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31138 lines
1.1 MiB
31138 lines
1.1 MiB
<!-- doc/src/sgml/func.sgml -->
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<chapter id="functions">
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<title>Functions and Operators</title>
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<indexterm zone="functions">
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<primary>function</primary>
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</indexterm>
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<indexterm zone="functions">
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<primary>operator</primary>
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</indexterm>
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<para>
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<productname>PostgreSQL</productname> provides a large number of
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functions and operators for the built-in data types. This chapter
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describes most of them, although additional special-purpose functions
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appear in relevant sections of the manual. Users can also
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define their own functions and operators, as described in
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<xref linkend="server-programming"/>. The
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<application>psql</application> commands <command>\df</command> and
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<command>\do</command> can be used to list all
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available functions and operators, respectively.
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</para>
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<para>
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The notation used throughout this chapter to describe the argument and
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result data types of a function or operator is like this:
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<synopsis>
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<function>repeat</function> ( <type>text</type>, <type>integer</type> ) <returnvalue>text</returnvalue>
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</synopsis>
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which says that the function <function>repeat</function> takes one text and
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one integer argument and returns a result of type text. The right arrow
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is also used to indicate the result of an example, thus:
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<programlisting>
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repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
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</programlisting>
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</para>
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<para>
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If you are concerned about portability then note that most of
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the functions and operators described in this chapter, with the
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exception of the most trivial arithmetic and comparison operators
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and some explicitly marked functions, are not specified by the
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<acronym>SQL</acronym> standard. Some of this extended functionality
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is present in other <acronym>SQL</acronym> database management
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systems, and in many cases this functionality is compatible and
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consistent between the various implementations.
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</para>
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<sect1 id="functions-logical">
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<title>Logical Operators</title>
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<indexterm zone="functions-logical">
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<primary>operator</primary>
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<secondary>logical</secondary>
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</indexterm>
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<indexterm>
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<primary>Boolean</primary>
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<secondary>operators</secondary>
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<see>operators, logical</see>
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</indexterm>
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<para>
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The usual logical operators are available:
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<indexterm>
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<primary>AND (operator)</primary>
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</indexterm>
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<indexterm>
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<primary>OR (operator)</primary>
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</indexterm>
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<indexterm>
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<primary>NOT (operator)</primary>
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</indexterm>
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<indexterm>
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<primary>conjunction</primary>
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</indexterm>
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<indexterm>
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<primary>disjunction</primary>
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</indexterm>
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<indexterm>
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<primary>negation</primary>
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</indexterm>
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<synopsis>
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<type>boolean</type> <literal>AND</literal> <type>boolean</type> <returnvalue>boolean</returnvalue>
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<type>boolean</type> <literal>OR</literal> <type>boolean</type> <returnvalue>boolean</returnvalue>
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<literal>NOT</literal> <type>boolean</type> <returnvalue>boolean</returnvalue>
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</synopsis>
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<acronym>SQL</acronym> uses a three-valued logic system with true,
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false, and <literal>null</literal>, which represents <quote>unknown</quote>.
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Observe the following truth tables:
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<informaltable>
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<tgroup cols="4">
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<thead>
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<row>
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<entry><replaceable>a</replaceable></entry>
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<entry><replaceable>b</replaceable></entry>
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<entry><replaceable>a</replaceable> AND <replaceable>b</replaceable></entry>
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<entry><replaceable>a</replaceable> OR <replaceable>b</replaceable></entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>TRUE</entry>
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<entry>TRUE</entry>
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<entry>TRUE</entry>
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<entry>TRUE</entry>
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</row>
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<row>
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<entry>TRUE</entry>
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<entry>FALSE</entry>
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<entry>FALSE</entry>
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<entry>TRUE</entry>
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</row>
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<row>
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<entry>TRUE</entry>
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<entry>NULL</entry>
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<entry>NULL</entry>
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<entry>TRUE</entry>
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</row>
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<row>
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<entry>FALSE</entry>
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<entry>FALSE</entry>
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<entry>FALSE</entry>
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<entry>FALSE</entry>
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</row>
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<row>
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<entry>FALSE</entry>
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<entry>NULL</entry>
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<entry>FALSE</entry>
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<entry>NULL</entry>
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</row>
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<row>
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<entry>NULL</entry>
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<entry>NULL</entry>
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<entry>NULL</entry>
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<entry>NULL</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry><replaceable>a</replaceable></entry>
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<entry>NOT <replaceable>a</replaceable></entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>TRUE</entry>
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<entry>FALSE</entry>
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</row>
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<row>
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<entry>FALSE</entry>
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<entry>TRUE</entry>
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</row>
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<row>
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<entry>NULL</entry>
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<entry>NULL</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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<para>
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The operators <literal>AND</literal> and <literal>OR</literal> are
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commutative, that is, you can switch the left and right operands
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without affecting the result. (However, it is not guaranteed that
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the left operand is evaluated before the right operand. See <xref
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linkend="syntax-express-eval"/> for more information about the
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order of evaluation of subexpressions.)
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</para>
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</sect1>
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<sect1 id="functions-comparison">
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<title>Comparison Functions and Operators</title>
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<indexterm zone="functions-comparison">
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<primary>comparison</primary>
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<secondary>operators</secondary>
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</indexterm>
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<para>
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The usual comparison operators are available, as shown in <xref
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linkend="functions-comparison-op-table"/>.
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</para>
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<table id="functions-comparison-op-table">
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<title>Comparison Operators</title>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Operator</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>
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<replaceable>datatype</replaceable> <literal><</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</entry>
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<entry>Less than</entry>
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</row>
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<row>
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<entry>
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<replaceable>datatype</replaceable> <literal>></literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</entry>
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<entry>Greater than</entry>
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</row>
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<row>
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<entry>
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<replaceable>datatype</replaceable> <literal><=</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</entry>
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<entry>Less than or equal to</entry>
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</row>
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<row>
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<entry>
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<replaceable>datatype</replaceable> <literal>>=</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</entry>
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<entry>Greater than or equal to</entry>
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</row>
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<row>
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<entry>
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<replaceable>datatype</replaceable> <literal>=</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</entry>
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<entry>Equal</entry>
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</row>
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<row>
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<entry>
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<replaceable>datatype</replaceable> <literal><></literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</entry>
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<entry>Not equal</entry>
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</row>
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<row>
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<entry>
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<replaceable>datatype</replaceable> <literal>!=</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</entry>
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<entry>Not equal</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<note>
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<para>
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<literal><></literal> is the standard SQL notation for <quote>not
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equal</quote>. <literal>!=</literal> is an alias, which is converted
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to <literal><></literal> at a very early stage of parsing.
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Hence, it is not possible to implement <literal>!=</literal>
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and <literal><></literal> operators that do different things.
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</para>
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</note>
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<para>
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These comparison operators are available for all built-in data types
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that have a natural ordering, including numeric, string, and date/time
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types. In addition, arrays, composite types, and ranges can be compared
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if their component data types are comparable.
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</para>
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<para>
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It is usually possible to compare values of related data
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types as well; for example <type>integer</type> <literal>></literal>
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<type>bigint</type> will work. Some cases of this sort are implemented
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directly by <quote>cross-type</quote> comparison operators, but if no
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such operator is available, the parser will coerce the less-general type
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to the more-general type and apply the latter's comparison operator.
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</para>
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<para>
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As shown above, all comparison operators are binary operators that
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return values of type <type>boolean</type>. Thus, expressions like
|
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<literal>1 < 2 < 3</literal> are not valid (because there is
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no <literal><</literal> operator to compare a Boolean value with
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<literal>3</literal>). Use the <literal>BETWEEN</literal> predicates
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shown below to perform range tests.
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</para>
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<para>
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There are also some comparison predicates, as shown in <xref
|
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linkend="functions-comparison-pred-table"/>. These behave much like
|
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operators, but have special syntax mandated by the SQL standard.
|
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</para>
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|
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<table id="functions-comparison-pred-table">
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<title>Comparison Predicates</title>
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<tgroup cols="1">
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<thead>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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Predicate
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</para>
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<para>
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Description
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</para>
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<para>
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Example(s)
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</para></entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<replaceable>datatype</replaceable> <literal>BETWEEN</literal> <replaceable>datatype</replaceable> <literal>AND</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Between (inclusive of the range endpoints).
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</para>
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<para>
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<literal>2 BETWEEN 1 AND 3</literal>
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<returnvalue>t</returnvalue>
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</para>
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<para>
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<literal>2 BETWEEN 3 AND 1</literal>
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<returnvalue>f</returnvalue>
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</para></entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<replaceable>datatype</replaceable> <literal>NOT BETWEEN</literal> <replaceable>datatype</replaceable> <literal>AND</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Not between (the negation of <literal>BETWEEN</literal>).
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</para>
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<para>
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<literal>2 NOT BETWEEN 1 AND 3</literal>
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<returnvalue>f</returnvalue>
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</para></entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<replaceable>datatype</replaceable> <literal>BETWEEN SYMMETRIC</literal> <replaceable>datatype</replaceable> <literal>AND</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Between, after sorting the two endpoint values.
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</para>
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<para>
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<literal>2 BETWEEN SYMMETRIC 3 AND 1</literal>
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<returnvalue>t</returnvalue>
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</para></entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<replaceable>datatype</replaceable> <literal>NOT BETWEEN SYMMETRIC</literal> <replaceable>datatype</replaceable> <literal>AND</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Not between, after sorting the two endpoint values.
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</para>
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<para>
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<literal>2 NOT BETWEEN SYMMETRIC 3 AND 1</literal>
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<returnvalue>f</returnvalue>
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</para></entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<replaceable>datatype</replaceable> <literal>IS DISTINCT FROM</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Not equal, treating null as a comparable value.
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</para>
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<para>
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<literal>1 IS DISTINCT FROM NULL</literal>
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<returnvalue>t</returnvalue> (rather than <literal>NULL</literal>)
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</para>
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<para>
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<literal>NULL IS DISTINCT FROM NULL</literal>
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<returnvalue>f</returnvalue> (rather than <literal>NULL</literal>)
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</para></entry>
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</row>
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|
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<row>
|
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<entry role="func_table_entry"><para role="func_signature">
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<replaceable>datatype</replaceable> <literal>IS NOT DISTINCT FROM</literal> <replaceable>datatype</replaceable>
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Equal, treating null as a comparable value.
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</para>
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<para>
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<literal>1 IS NOT DISTINCT FROM NULL</literal>
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<returnvalue>f</returnvalue> (rather than <literal>NULL</literal>)
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</para>
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<para>
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<literal>NULL IS NOT DISTINCT FROM NULL</literal>
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<returnvalue>t</returnvalue> (rather than <literal>NULL</literal>)
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</para></entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<replaceable>datatype</replaceable> <literal>IS NULL</literal>
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Test whether value is null.
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</para>
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<para>
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<literal>1.5 IS NULL</literal>
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<returnvalue>f</returnvalue>
|
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</para></entry>
|
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</row>
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|
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<row>
|
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<entry role="func_table_entry"><para role="func_signature">
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<replaceable>datatype</replaceable> <literal>IS NOT NULL</literal>
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<returnvalue>boolean</returnvalue>
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</para>
|
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<para>
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Test whether value is not null.
|
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</para>
|
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<para>
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<literal>'null' IS NOT NULL</literal>
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<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>datatype</replaceable> <literal>ISNULL</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test whether value is null (nonstandard syntax).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>datatype</replaceable> <literal>NOTNULL</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test whether value is not null (nonstandard syntax).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>boolean</type> <literal>IS TRUE</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test whether boolean expression yields true.
|
|
</para>
|
|
<para>
|
|
<literal>true IS TRUE</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>NULL::boolean IS TRUE</literal>
|
|
<returnvalue>f</returnvalue> (rather than <literal>NULL</literal>)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>boolean</type> <literal>IS NOT TRUE</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test whether boolean expression yields false or unknown.
|
|
</para>
|
|
<para>
|
|
<literal>true IS NOT TRUE</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>NULL::boolean IS NOT TRUE</literal>
|
|
<returnvalue>t</returnvalue> (rather than <literal>NULL</literal>)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>boolean</type> <literal>IS FALSE</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test whether boolean expression yields false.
|
|
</para>
|
|
<para>
|
|
<literal>true IS FALSE</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>NULL::boolean IS FALSE</literal>
|
|
<returnvalue>f</returnvalue> (rather than <literal>NULL</literal>)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>boolean</type> <literal>IS NOT FALSE</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test whether boolean expression yields true or unknown.
|
|
</para>
|
|
<para>
|
|
<literal>true IS NOT FALSE</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>NULL::boolean IS NOT FALSE</literal>
|
|
<returnvalue>t</returnvalue> (rather than <literal>NULL</literal>)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>boolean</type> <literal>IS UNKNOWN</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test whether boolean expression yields unknown.
|
|
</para>
|
|
<para>
|
|
<literal>true IS UNKNOWN</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>NULL::boolean IS UNKNOWN</literal>
|
|
<returnvalue>t</returnvalue> (rather than <literal>NULL</literal>)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>boolean</type> <literal>IS NOT UNKNOWN</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test whether boolean expression yields true or false.
|
|
</para>
|
|
<para>
|
|
<literal>true IS NOT UNKNOWN</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>NULL::boolean IS NOT UNKNOWN</literal>
|
|
<returnvalue>f</returnvalue> (rather than <literal>NULL</literal>)
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<indexterm>
|
|
<primary>BETWEEN</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>BETWEEN SYMMETRIC</primary>
|
|
</indexterm>
|
|
The <token>BETWEEN</token> predicate simplifies range tests:
|
|
<synopsis>
|
|
<replaceable>a</replaceable> BETWEEN <replaceable>x</replaceable> AND <replaceable>y</replaceable>
|
|
</synopsis>
|
|
is equivalent to
|
|
<synopsis>
|
|
<replaceable>a</replaceable> >= <replaceable>x</replaceable> AND <replaceable>a</replaceable> <= <replaceable>y</replaceable>
|
|
</synopsis>
|
|
Notice that <token>BETWEEN</token> treats the endpoint values as included
|
|
in the range.
|
|
<literal>BETWEEN SYMMETRIC</literal> is like <literal>BETWEEN</literal>
|
|
except there is no requirement that the argument to the left of
|
|
<literal>AND</literal> be less than or equal to the argument on the right.
|
|
If it is not, those two arguments are automatically swapped, so that
|
|
a nonempty range is always implied.
|
|
</para>
|
|
|
|
<para>
|
|
The various variants of <literal>BETWEEN</literal> are implemented in
|
|
terms of the ordinary comparison operators, and therefore will work for
|
|
any data type(s) that can be compared.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
The use of <literal>AND</literal> in the <literal>BETWEEN</literal>
|
|
syntax creates an ambiguity with the use of <literal>AND</literal> as a
|
|
logical operator. To resolve this, only a limited set of expression
|
|
types are allowed as the second argument of a <literal>BETWEEN</literal>
|
|
clause. If you need to write a more complex sub-expression
|
|
in <literal>BETWEEN</literal>, write parentheses around the
|
|
sub-expression.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
<indexterm>
|
|
<primary>IS DISTINCT FROM</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>IS NOT DISTINCT FROM</primary>
|
|
</indexterm>
|
|
Ordinary comparison operators yield null (signifying <quote>unknown</quote>),
|
|
not true or false, when either input is null. For example,
|
|
<literal>7 = NULL</literal> yields null, as does <literal>7 <> NULL</literal>. When
|
|
this behavior is not suitable, use the
|
|
<literal>IS <optional> NOT </optional> DISTINCT FROM</literal> predicates:
|
|
<synopsis>
|
|
<replaceable>a</replaceable> IS DISTINCT FROM <replaceable>b</replaceable>
|
|
<replaceable>a</replaceable> IS NOT DISTINCT FROM <replaceable>b</replaceable>
|
|
</synopsis>
|
|
For non-null inputs, <literal>IS DISTINCT FROM</literal> is
|
|
the same as the <literal><></literal> operator. However, if both
|
|
inputs are null it returns false, and if only one input is
|
|
null it returns true. Similarly, <literal>IS NOT DISTINCT
|
|
FROM</literal> is identical to <literal>=</literal> for non-null
|
|
inputs, but it returns true when both inputs are null, and false when only
|
|
one input is null. Thus, these predicates effectively act as though null
|
|
were a normal data value, rather than <quote>unknown</quote>.
|
|
</para>
|
|
|
|
<para>
|
|
<indexterm>
|
|
<primary>IS NULL</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>IS NOT NULL</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>ISNULL</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>NOTNULL</primary>
|
|
</indexterm>
|
|
To check whether a value is or is not null, use the predicates:
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> IS NULL
|
|
<replaceable>expression</replaceable> IS NOT NULL
|
|
</synopsis>
|
|
or the equivalent, but nonstandard, predicates:
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> ISNULL
|
|
<replaceable>expression</replaceable> NOTNULL
|
|
</synopsis>
|
|
<indexterm><primary>null value</primary><secondary>comparing</secondary></indexterm>
|
|
</para>
|
|
|
|
<para>
|
|
Do <emphasis>not</emphasis> write
|
|
<literal><replaceable>expression</replaceable> = NULL</literal>
|
|
because <literal>NULL</literal> is not <quote>equal to</quote>
|
|
<literal>NULL</literal>. (The null value represents an unknown value,
|
|
and it is not known whether two unknown values are equal.)
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
Some applications might expect that
|
|
<literal><replaceable>expression</replaceable> = NULL</literal>
|
|
returns true if <replaceable>expression</replaceable> evaluates to
|
|
the null value. It is highly recommended that these applications
|
|
be modified to comply with the SQL standard. However, if that
|
|
cannot be done the <xref linkend="guc-transform-null-equals"/>
|
|
configuration variable is available. If it is enabled,
|
|
<productname>PostgreSQL</productname> will convert <literal>x =
|
|
NULL</literal> clauses to <literal>x IS NULL</literal>.
|
|
</para>
|
|
</tip>
|
|
|
|
<para>
|
|
If the <replaceable>expression</replaceable> is row-valued, then
|
|
<literal>IS NULL</literal> is true when the row expression itself is null
|
|
or when all the row's fields are null, while
|
|
<literal>IS NOT NULL</literal> is true when the row expression itself is non-null
|
|
and all the row's fields are non-null. Because of this behavior,
|
|
<literal>IS NULL</literal> and <literal>IS NOT NULL</literal> do not always return
|
|
inverse results for row-valued expressions; in particular, a row-valued
|
|
expression that contains both null and non-null fields will return false
|
|
for both tests. For example:
|
|
|
|
<programlisting>
|
|
SELECT ROW(1,2.5,'this is a test') = ROW(1, 3, 'not the same');
|
|
|
|
SELECT ROW(table.*) IS NULL FROM table; -- detect all-null rows
|
|
|
|
SELECT ROW(table.*) IS NOT NULL FROM table; -- detect all-non-null rows
|
|
|
|
SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in rows
|
|
</programlisting>
|
|
|
|
In some cases, it may be preferable to
|
|
write <replaceable>row</replaceable> <literal>IS DISTINCT FROM NULL</literal>
|
|
or <replaceable>row</replaceable> <literal>IS NOT DISTINCT FROM NULL</literal>,
|
|
which will simply check whether the overall row value is null without any
|
|
additional tests on the row fields.
|
|
</para>
|
|
|
|
<para>
|
|
<indexterm>
|
|
<primary>IS TRUE</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>IS NOT TRUE</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>IS FALSE</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>IS NOT FALSE</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>IS UNKNOWN</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>IS NOT UNKNOWN</primary>
|
|
</indexterm>
|
|
Boolean values can also be tested using the predicates
|
|
<synopsis>
|
|
<replaceable>boolean_expression</replaceable> IS TRUE
|
|
<replaceable>boolean_expression</replaceable> IS NOT TRUE
|
|
<replaceable>boolean_expression</replaceable> IS FALSE
|
|
<replaceable>boolean_expression</replaceable> IS NOT FALSE
|
|
<replaceable>boolean_expression</replaceable> IS UNKNOWN
|
|
<replaceable>boolean_expression</replaceable> IS NOT UNKNOWN
|
|
</synopsis>
|
|
These will always return true or false, never a null value, even when the
|
|
operand is null.
|
|
A null input is treated as the logical value <quote>unknown</quote>.
|
|
Notice that <literal>IS UNKNOWN</literal> and <literal>IS NOT UNKNOWN</literal> are
|
|
effectively the same as <literal>IS NULL</literal> and
|
|
<literal>IS NOT NULL</literal>, respectively, except that the input
|
|
expression must be of Boolean type.
|
|
</para>
|
|
|
|
<para>
|
|
Some comparison-related functions are also available, as shown in <xref
|
|
linkend="functions-comparison-func-table"/>.
|
|
</para>
|
|
|
|
<table id="functions-comparison-func-table">
|
|
<title>Comparison Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>num_nonnulls</primary>
|
|
</indexterm>
|
|
<function>num_nonnulls</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of non-null arguments.
|
|
</para>
|
|
<para>
|
|
<literal>num_nonnulls(1, NULL, 2)</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>num_nulls</primary>
|
|
</indexterm>
|
|
<function>num_nulls</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of null arguments.
|
|
</para>
|
|
<para>
|
|
<literal>num_nulls(1, NULL, 2)</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="functions-math">
|
|
<title>Mathematical Functions and Operators</title>
|
|
|
|
<para>
|
|
Mathematical operators are provided for many
|
|
<productname>PostgreSQL</productname> types. For types without
|
|
standard mathematical conventions
|
|
(e.g., date/time types) we
|
|
describe the actual behavior in subsequent sections.
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="functions-math-op-table"/> shows the mathematical
|
|
operators that are available for the standard numeric types.
|
|
Unless otherwise noted, operators shown as
|
|
accepting <replaceable>numeric_type</replaceable> are available for all
|
|
the types <type>smallint</type>, <type>integer</type>,
|
|
<type>bigint</type>, <type>numeric</type>, <type>real</type>,
|
|
and <type>double precision</type>.
|
|
Operators shown as accepting <replaceable>integral_type</replaceable>
|
|
are available for the types <type>smallint</type>, <type>integer</type>,
|
|
and <type>bigint</type>.
|
|
Except where noted, each form of an operator returns the same data type
|
|
as its argument(s). Calls involving multiple argument data types, such
|
|
as <type>integer</type> <literal>+</literal> <type>numeric</type>,
|
|
are resolved by using the type appearing later in these lists.
|
|
</para>
|
|
|
|
<table id="functions-math-op-table">
|
|
<title>Mathematical Operators</title>
|
|
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>numeric_type</replaceable> <literal>+</literal> <replaceable>numeric_type</replaceable>
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Addition
|
|
</para>
|
|
<para>
|
|
<literal>2 + 3</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>+</literal> <replaceable>numeric_type</replaceable>
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Unary plus (no operation)
|
|
</para>
|
|
<para>
|
|
<literal>+ 3.5</literal>
|
|
<returnvalue>3.5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>numeric_type</replaceable> <literal>-</literal> <replaceable>numeric_type</replaceable>
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtraction
|
|
</para>
|
|
<para>
|
|
<literal>2 - 3</literal>
|
|
<returnvalue>-1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>-</literal> <replaceable>numeric_type</replaceable>
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Negation
|
|
</para>
|
|
<para>
|
|
<literal>- (-4)</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>numeric_type</replaceable> <literal>*</literal> <replaceable>numeric_type</replaceable>
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Multiplication
|
|
</para>
|
|
<para>
|
|
<literal>2 * 3</literal>
|
|
<returnvalue>6</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>numeric_type</replaceable> <literal>/</literal> <replaceable>numeric_type</replaceable>
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Division (for integral types, division truncates the result towards
|
|
zero)
|
|
</para>
|
|
<para>
|
|
<literal>5.0 / 2</literal>
|
|
<returnvalue>2.5000000000000000</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>5 / 2</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>(-5) / 2</literal>
|
|
<returnvalue>-2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>numeric_type</replaceable> <literal>%</literal> <replaceable>numeric_type</replaceable>
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Modulo (remainder); available for <type>smallint</type>,
|
|
<type>integer</type>, <type>bigint</type>, and <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
<literal>5 % 4</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>numeric</type> <literal>^</literal> <type>numeric</type>
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>double precision</type> <literal>^</literal> <type>double precision</type>
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Exponentiation
|
|
</para>
|
|
<para>
|
|
<literal>2 ^ 3</literal>
|
|
<returnvalue>8</returnvalue>
|
|
</para>
|
|
<para>
|
|
Unlike typical mathematical practice, multiple uses of
|
|
<literal>^</literal> will associate left to right by default:
|
|
</para>
|
|
<para>
|
|
<literal>2 ^ 3 ^ 3</literal>
|
|
<returnvalue>512</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>2 ^ (3 ^ 3)</literal>
|
|
<returnvalue>134217728</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>|/</literal> <type>double precision</type>
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Square root
|
|
</para>
|
|
<para>
|
|
<literal>|/ 25.0</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>||/</literal> <type>double precision</type>
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cube root
|
|
</para>
|
|
<para>
|
|
<literal>||/ 64.0</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>@</literal> <replaceable>numeric_type</replaceable>
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Absolute value
|
|
</para>
|
|
<para>
|
|
<literal>@ -5.0</literal>
|
|
<returnvalue>5.0</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>integral_type</replaceable> <literal>&</literal> <replaceable>integral_type</replaceable>
|
|
<returnvalue><replaceable>integral_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise AND
|
|
</para>
|
|
<para>
|
|
<literal>91 & 15</literal>
|
|
<returnvalue>11</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>integral_type</replaceable> <literal>|</literal> <replaceable>integral_type</replaceable>
|
|
<returnvalue><replaceable>integral_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise OR
|
|
</para>
|
|
<para>
|
|
<literal>32 | 3</literal>
|
|
<returnvalue>35</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>integral_type</replaceable> <literal>#</literal> <replaceable>integral_type</replaceable>
|
|
<returnvalue><replaceable>integral_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise exclusive OR
|
|
</para>
|
|
<para>
|
|
<literal>17 # 5</literal>
|
|
<returnvalue>20</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>~</literal> <replaceable>integral_type</replaceable>
|
|
<returnvalue><replaceable>integral_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise NOT
|
|
</para>
|
|
<para>
|
|
<literal>~1</literal>
|
|
<returnvalue>-2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>integral_type</replaceable> <literal><<</literal> <type>integer</type>
|
|
<returnvalue><replaceable>integral_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise shift left
|
|
</para>
|
|
<para>
|
|
<literal>1 << 4</literal>
|
|
<returnvalue>16</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>integral_type</replaceable> <literal>>></literal> <type>integer</type>
|
|
<returnvalue><replaceable>integral_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise shift right
|
|
</para>
|
|
<para>
|
|
<literal>8 >> 2</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-math-func-table"/> shows the available
|
|
mathematical functions.
|
|
Many of these functions are provided in multiple forms with different
|
|
argument types.
|
|
Except where noted, any given form of a function returns the same
|
|
data type as its argument(s); cross-type cases are resolved in the
|
|
same way as explained above for operators.
|
|
The functions working with <type>double precision</type> data are mostly
|
|
implemented on top of the host system's C library; accuracy and behavior in
|
|
boundary cases can therefore vary depending on the host system.
|
|
</para>
|
|
|
|
<table id="functions-math-func-table">
|
|
<title>Mathematical Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>abs</primary>
|
|
</indexterm>
|
|
<function>abs</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Absolute value
|
|
</para>
|
|
<para>
|
|
<literal>abs(-17.4)</literal>
|
|
<returnvalue>17.4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cbrt</primary>
|
|
</indexterm>
|
|
<function>cbrt</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cube root
|
|
</para>
|
|
<para>
|
|
<literal>cbrt(64.0)</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ceil</primary>
|
|
</indexterm>
|
|
<function>ceil</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>ceil</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Nearest integer greater than or equal to argument
|
|
</para>
|
|
<para>
|
|
<literal>ceil(42.2)</literal>
|
|
<returnvalue>43</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>ceil(-42.8)</literal>
|
|
<returnvalue>-42</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ceiling</primary>
|
|
</indexterm>
|
|
<function>ceiling</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>ceiling</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Nearest integer greater than or equal to argument (same
|
|
as <function>ceil</function>)
|
|
</para>
|
|
<para>
|
|
<literal>ceiling(95.3)</literal>
|
|
<returnvalue>96</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>degrees</primary>
|
|
</indexterm>
|
|
<function>degrees</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts radians to degrees
|
|
</para>
|
|
<para>
|
|
<literal>degrees(0.5)</literal>
|
|
<returnvalue>28.64788975654116</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>div</primary>
|
|
</indexterm>
|
|
<function>div</function> ( <parameter>y</parameter> <type>numeric</type>,
|
|
<parameter>x</parameter> <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Integer quotient of <parameter>y</parameter>/<parameter>x</parameter>
|
|
(truncates towards zero)
|
|
</para>
|
|
<para>
|
|
<literal>div(9, 4)</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>erf</primary>
|
|
</indexterm>
|
|
<function>erf</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Error function
|
|
</para>
|
|
<para>
|
|
<literal>erf(1.0)</literal>
|
|
<returnvalue>0.8427007929497149</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>erfc</primary>
|
|
</indexterm>
|
|
<function>erfc</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Complementary error function (<literal>1 - erf(x)</literal>, without
|
|
loss of precision for large inputs)
|
|
</para>
|
|
<para>
|
|
<literal>erfc(1.0)</literal>
|
|
<returnvalue>0.15729920705028513</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>exp</primary>
|
|
</indexterm>
|
|
<function>exp</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>exp</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Exponential (<literal>e</literal> raised to the given power)
|
|
</para>
|
|
<para>
|
|
<literal>exp(1.0)</literal>
|
|
<returnvalue>2.7182818284590452</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm id="function-factorial">
|
|
<primary>factorial</primary>
|
|
</indexterm>
|
|
<function>factorial</function> ( <type>bigint</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Factorial
|
|
</para>
|
|
<para>
|
|
<literal>factorial(5)</literal>
|
|
<returnvalue>120</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>floor</primary>
|
|
</indexterm>
|
|
<function>floor</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>floor</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Nearest integer less than or equal to argument
|
|
</para>
|
|
<para>
|
|
<literal>floor(42.8)</literal>
|
|
<returnvalue>42</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>floor(-42.8)</literal>
|
|
<returnvalue>-43</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>gcd</primary>
|
|
</indexterm>
|
|
<function>gcd</function> ( <replaceable>numeric_type</replaceable>, <replaceable>numeric_type</replaceable> )
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Greatest common divisor (the largest positive number that divides both
|
|
inputs with no remainder); returns <literal>0</literal> if both inputs
|
|
are zero; available for <type>integer</type>, <type>bigint</type>,
|
|
and <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
<literal>gcd(1071, 462)</literal>
|
|
<returnvalue>21</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lcm</primary>
|
|
</indexterm>
|
|
<function>lcm</function> ( <replaceable>numeric_type</replaceable>, <replaceable>numeric_type</replaceable> )
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Least common multiple (the smallest strictly positive number that is
|
|
an integral multiple of both inputs); returns <literal>0</literal> if
|
|
either input is zero; available for <type>integer</type>,
|
|
<type>bigint</type>, and <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
<literal>lcm(1071, 462)</literal>
|
|
<returnvalue>23562</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ln</primary>
|
|
</indexterm>
|
|
<function>ln</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>ln</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Natural logarithm
|
|
</para>
|
|
<para>
|
|
<literal>ln(2.0)</literal>
|
|
<returnvalue>0.6931471805599453</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>log</primary>
|
|
</indexterm>
|
|
<function>log</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>log</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Base 10 logarithm
|
|
</para>
|
|
<para>
|
|
<literal>log(100)</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>log10</primary>
|
|
</indexterm>
|
|
<function>log10</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>log10</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Base 10 logarithm (same as <function>log</function>)
|
|
</para>
|
|
<para>
|
|
<literal>log10(1000)</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>log</function> ( <parameter>b</parameter> <type>numeric</type>,
|
|
<parameter>x</parameter> <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Logarithm of <parameter>x</parameter> to base <parameter>b</parameter>
|
|
</para>
|
|
<para>
|
|
<literal>log(2.0, 64.0)</literal>
|
|
<returnvalue>6.0000000000000000</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>min_scale</primary>
|
|
</indexterm>
|
|
<function>min_scale</function> ( <type>numeric</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Minimum scale (number of fractional decimal digits) needed
|
|
to represent the supplied value precisely
|
|
</para>
|
|
<para>
|
|
<literal>min_scale(8.4100)</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>mod</primary>
|
|
</indexterm>
|
|
<function>mod</function> ( <parameter>y</parameter> <replaceable>numeric_type</replaceable>,
|
|
<parameter>x</parameter> <replaceable>numeric_type</replaceable> )
|
|
<returnvalue><replaceable>numeric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Remainder of <parameter>y</parameter>/<parameter>x</parameter>;
|
|
available for <type>smallint</type>, <type>integer</type>,
|
|
<type>bigint</type>, and <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
<literal>mod(9, 4)</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pi</primary>
|
|
</indexterm>
|
|
<function>pi</function> ( )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Approximate value of <phrase role="symbol_font">π</phrase>
|
|
</para>
|
|
<para>
|
|
<literal>pi()</literal>
|
|
<returnvalue>3.141592653589793</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>power</primary>
|
|
</indexterm>
|
|
<function>power</function> ( <parameter>a</parameter> <type>numeric</type>,
|
|
<parameter>b</parameter> <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>power</function> ( <parameter>a</parameter> <type>double precision</type>,
|
|
<parameter>b</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
<parameter>a</parameter> raised to the power of <parameter>b</parameter>
|
|
</para>
|
|
<para>
|
|
<literal>power(9, 3)</literal>
|
|
<returnvalue>729</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>radians</primary>
|
|
</indexterm>
|
|
<function>radians</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts degrees to radians
|
|
</para>
|
|
<para>
|
|
<literal>radians(45.0)</literal>
|
|
<returnvalue>0.7853981633974483</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>round</primary>
|
|
</indexterm>
|
|
<function>round</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>round</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Rounds to nearest integer. For <type>numeric</type>, ties are
|
|
broken by rounding away from zero. For <type>double precision</type>,
|
|
the tie-breaking behavior is platform dependent, but
|
|
<quote>round to nearest even</quote> is the most common rule.
|
|
</para>
|
|
<para>
|
|
<literal>round(42.4)</literal>
|
|
<returnvalue>42</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>round</function> ( <parameter>v</parameter> <type>numeric</type>, <parameter>s</parameter> <type>integer</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Rounds <parameter>v</parameter> to <parameter>s</parameter> decimal
|
|
places. Ties are broken by rounding away from zero.
|
|
</para>
|
|
<para>
|
|
<literal>round(42.4382, 2)</literal>
|
|
<returnvalue>42.44</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>round(1234.56, -1)</literal>
|
|
<returnvalue>1230</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>scale</primary>
|
|
</indexterm>
|
|
<function>scale</function> ( <type>numeric</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Scale of the argument (the number of decimal digits in the fractional part)
|
|
</para>
|
|
<para>
|
|
<literal>scale(8.4100)</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sign</primary>
|
|
</indexterm>
|
|
<function>sign</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sign</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sign of the argument (-1, 0, or +1)
|
|
</para>
|
|
<para>
|
|
<literal>sign(-8.4)</literal>
|
|
<returnvalue>-1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sqrt</primary>
|
|
</indexterm>
|
|
<function>sqrt</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sqrt</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Square root
|
|
</para>
|
|
<para>
|
|
<literal>sqrt(2)</literal>
|
|
<returnvalue>1.4142135623730951</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>trim_scale</primary>
|
|
</indexterm>
|
|
<function>trim_scale</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reduces the value's scale (number of fractional decimal digits) by
|
|
removing trailing zeroes
|
|
</para>
|
|
<para>
|
|
<literal>trim_scale(8.4100)</literal>
|
|
<returnvalue>8.41</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>trunc</primary>
|
|
</indexterm>
|
|
<function>trunc</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>trunc</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Truncates to integer (towards zero)
|
|
</para>
|
|
<para>
|
|
<literal>trunc(42.8)</literal>
|
|
<returnvalue>42</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>trunc(-42.8)</literal>
|
|
<returnvalue>-42</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>trunc</function> ( <parameter>v</parameter> <type>numeric</type>, <parameter>s</parameter> <type>integer</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Truncates <parameter>v</parameter> to <parameter>s</parameter>
|
|
decimal places
|
|
</para>
|
|
<para>
|
|
<literal>trunc(42.4382, 2)</literal>
|
|
<returnvalue>42.43</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>width_bucket</primary>
|
|
</indexterm>
|
|
<function>width_bucket</function> ( <parameter>operand</parameter> <type>numeric</type>, <parameter>low</parameter> <type>numeric</type>, <parameter>high</parameter> <type>numeric</type>, <parameter>count</parameter> <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>width_bucket</function> ( <parameter>operand</parameter> <type>double precision</type>, <parameter>low</parameter> <type>double precision</type>, <parameter>high</parameter> <type>double precision</type>, <parameter>count</parameter> <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of the bucket in
|
|
which <parameter>operand</parameter> falls in a histogram
|
|
having <parameter>count</parameter> equal-width buckets spanning the
|
|
range <parameter>low</parameter> to <parameter>high</parameter>.
|
|
Returns <literal>0</literal>
|
|
or <literal><parameter>count</parameter>+1</literal> for an input
|
|
outside that range.
|
|
</para>
|
|
<para>
|
|
<literal>width_bucket(5.35, 0.024, 10.06, 5)</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>width_bucket</function> ( <parameter>operand</parameter> <type>anycompatible</type>, <parameter>thresholds</parameter> <type>anycompatiblearray</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of the bucket in
|
|
which <parameter>operand</parameter> falls given an array listing the
|
|
lower bounds of the buckets. Returns <literal>0</literal> for an
|
|
input less than the first lower
|
|
bound. <parameter>operand</parameter> and the array elements can be
|
|
of any type having standard comparison operators.
|
|
The <parameter>thresholds</parameter> array <emphasis>must be
|
|
sorted</emphasis>, smallest first, or unexpected results will be
|
|
obtained.
|
|
</para>
|
|
<para>
|
|
<literal>width_bucket(now(), array['yesterday', 'today', 'tomorrow']::timestamptz[])</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-math-random-table"/> shows functions for
|
|
generating random numbers.
|
|
</para>
|
|
|
|
<table id="functions-math-random-table">
|
|
<title>Random Functions</title>
|
|
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>random</primary>
|
|
</indexterm>
|
|
<function>random</function> ( )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a random value in the range 0.0 <= x < 1.0
|
|
</para>
|
|
<para>
|
|
<literal>random()</literal>
|
|
<returnvalue>0.897124072839091</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>random</primary>
|
|
</indexterm>
|
|
<function>random</function> ( <parameter>min</parameter> <type>integer</type>, <parameter>max</parameter> <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>random</function> ( <parameter>min</parameter> <type>bigint</type>, <parameter>max</parameter> <type>bigint</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>random</function> ( <parameter>min</parameter> <type>numeric</type>, <parameter>max</parameter> <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a random value in the range
|
|
<parameter>min</parameter> <= x <= <parameter>max</parameter>.
|
|
For type <type>numeric</type>, the result will have the same number of
|
|
fractional decimal digits as <parameter>min</parameter> or
|
|
<parameter>max</parameter>, whichever has more.
|
|
</para>
|
|
<para>
|
|
<literal>random(1, 10)</literal>
|
|
<returnvalue>7</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>random(-0.499, 0.499)</literal>
|
|
<returnvalue>0.347</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>random_normal</primary>
|
|
</indexterm>
|
|
|
|
<function>random_normal</function> (
|
|
<optional> <parameter>mean</parameter> <type>double precision</type>
|
|
<optional>, <parameter>stddev</parameter> <type>double precision</type> </optional></optional> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a random value from the normal distribution with the given
|
|
parameters; <parameter>mean</parameter> defaults to 0.0
|
|
and <parameter>stddev</parameter> defaults to 1.0
|
|
</para>
|
|
<para>
|
|
<literal>random_normal(0.0, 1.0)</literal>
|
|
<returnvalue>0.051285419</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>setseed</primary>
|
|
</indexterm>
|
|
<function>setseed</function> ( <type>double precision</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets the seed for subsequent <literal>random()</literal> and
|
|
<literal>random_normal()</literal> calls;
|
|
argument must be between -1.0 and 1.0, inclusive
|
|
</para>
|
|
<para>
|
|
<literal>setseed(0.12345)</literal>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The <function>random()</function> and <function>random_normal()</function>
|
|
functions listed in <xref linkend="functions-math-random-table"/> use a
|
|
deterministic pseudo-random number generator.
|
|
It is fast but not suitable for cryptographic
|
|
applications; see the <xref linkend="pgcrypto"/> module for a more
|
|
secure alternative.
|
|
If <function>setseed()</function> is called, the series of results of
|
|
subsequent calls to these functions in the current session
|
|
can be repeated by re-issuing <function>setseed()</function> with the same
|
|
argument.
|
|
Without any prior <function>setseed()</function> call in the same
|
|
session, the first call to any of these functions obtains a seed
|
|
from a platform-dependent source of random bits.
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="functions-math-trig-table"/> shows the
|
|
available trigonometric functions. Each of these functions comes in
|
|
two variants, one that measures angles in radians and one that
|
|
measures angles in degrees.
|
|
</para>
|
|
|
|
<table id="functions-math-trig-table">
|
|
<title>Trigonometric Functions</title>
|
|
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>acos</primary>
|
|
</indexterm>
|
|
<function>acos</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse cosine, result in radians
|
|
</para>
|
|
<para>
|
|
<literal>acos(1)</literal>
|
|
<returnvalue>0</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>acosd</primary>
|
|
</indexterm>
|
|
<function>acosd</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse cosine, result in degrees
|
|
</para>
|
|
<para>
|
|
<literal>acosd(0.5)</literal>
|
|
<returnvalue>60</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>asin</primary>
|
|
</indexterm>
|
|
<function>asin</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse sine, result in radians
|
|
</para>
|
|
<para>
|
|
<literal>asin(1)</literal>
|
|
<returnvalue>1.5707963267948966</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>asind</primary>
|
|
</indexterm>
|
|
<function>asind</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse sine, result in degrees
|
|
</para>
|
|
<para>
|
|
<literal>asind(0.5)</literal>
|
|
<returnvalue>30</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>atan</primary>
|
|
</indexterm>
|
|
<function>atan</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse tangent, result in radians
|
|
</para>
|
|
<para>
|
|
<literal>atan(1)</literal>
|
|
<returnvalue>0.7853981633974483</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>atand</primary>
|
|
</indexterm>
|
|
<function>atand</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse tangent, result in degrees
|
|
</para>
|
|
<para>
|
|
<literal>atand(1)</literal>
|
|
<returnvalue>45</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>atan2</primary>
|
|
</indexterm>
|
|
<function>atan2</function> ( <parameter>y</parameter> <type>double precision</type>,
|
|
<parameter>x</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse tangent of
|
|
<parameter>y</parameter>/<parameter>x</parameter>,
|
|
result in radians
|
|
</para>
|
|
<para>
|
|
<literal>atan2(1, 0)</literal>
|
|
<returnvalue>1.5707963267948966</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>atan2d</primary>
|
|
</indexterm>
|
|
<function>atan2d</function> ( <parameter>y</parameter> <type>double precision</type>,
|
|
<parameter>x</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse tangent of
|
|
<parameter>y</parameter>/<parameter>x</parameter>,
|
|
result in degrees
|
|
</para>
|
|
<para>
|
|
<literal>atan2d(1, 0)</literal>
|
|
<returnvalue>90</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cos</primary>
|
|
</indexterm>
|
|
<function>cos</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cosine, argument in radians
|
|
</para>
|
|
<para>
|
|
<literal>cos(0)</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cosd</primary>
|
|
</indexterm>
|
|
<function>cosd</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cosine, argument in degrees
|
|
</para>
|
|
<para>
|
|
<literal>cosd(60)</literal>
|
|
<returnvalue>0.5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cot</primary>
|
|
</indexterm>
|
|
<function>cot</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cotangent, argument in radians
|
|
</para>
|
|
<para>
|
|
<literal>cot(0.5)</literal>
|
|
<returnvalue>1.830487721712452</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cotd</primary>
|
|
</indexterm>
|
|
<function>cotd</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cotangent, argument in degrees
|
|
</para>
|
|
<para>
|
|
<literal>cotd(45)</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sin</primary>
|
|
</indexterm>
|
|
<function>sin</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sine, argument in radians
|
|
</para>
|
|
<para>
|
|
<literal>sin(1)</literal>
|
|
<returnvalue>0.8414709848078965</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sind</primary>
|
|
</indexterm>
|
|
<function>sind</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sine, argument in degrees
|
|
</para>
|
|
<para>
|
|
<literal>sind(30)</literal>
|
|
<returnvalue>0.5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>tan</primary>
|
|
</indexterm>
|
|
<function>tan</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tangent, argument in radians
|
|
</para>
|
|
<para>
|
|
<literal>tan(1)</literal>
|
|
<returnvalue>1.5574077246549023</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>tand</primary>
|
|
</indexterm>
|
|
<function>tand</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tangent, argument in degrees
|
|
</para>
|
|
<para>
|
|
<literal>tand(45)</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>
|
|
Another way to work with angles measured in degrees is to use the unit
|
|
transformation functions <literal><function>radians()</function></literal>
|
|
and <literal><function>degrees()</function></literal> shown earlier.
|
|
However, using the degree-based trigonometric functions is preferred,
|
|
as that way avoids round-off error for special cases such
|
|
as <literal>sind(30)</literal>.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
<xref linkend="functions-math-hyp-table"/> shows the
|
|
available hyperbolic functions.
|
|
</para>
|
|
|
|
<table id="functions-math-hyp-table">
|
|
<title>Hyperbolic Functions</title>
|
|
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sinh</primary>
|
|
</indexterm>
|
|
<function>sinh</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Hyperbolic sine
|
|
</para>
|
|
<para>
|
|
<literal>sinh(1)</literal>
|
|
<returnvalue>1.1752011936438014</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cosh</primary>
|
|
</indexterm>
|
|
<function>cosh</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Hyperbolic cosine
|
|
</para>
|
|
<para>
|
|
<literal>cosh(0)</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>tanh</primary>
|
|
</indexterm>
|
|
<function>tanh</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Hyperbolic tangent
|
|
</para>
|
|
<para>
|
|
<literal>tanh(1)</literal>
|
|
<returnvalue>0.7615941559557649</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>asinh</primary>
|
|
</indexterm>
|
|
<function>asinh</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse hyperbolic sine
|
|
</para>
|
|
<para>
|
|
<literal>asinh(1)</literal>
|
|
<returnvalue>0.881373587019543</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>acosh</primary>
|
|
</indexterm>
|
|
<function>acosh</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse hyperbolic cosine
|
|
</para>
|
|
<para>
|
|
<literal>acosh(1)</literal>
|
|
<returnvalue>0</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>atanh</primary>
|
|
</indexterm>
|
|
<function>atanh</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Inverse hyperbolic tangent
|
|
</para>
|
|
<para>
|
|
<literal>atanh(0.5)</literal>
|
|
<returnvalue>0.5493061443340548</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-string">
|
|
<title>String Functions and Operators</title>
|
|
|
|
<para>
|
|
This section describes functions and operators for examining and
|
|
manipulating string values. Strings in this context include values
|
|
of the types <type>character</type>, <type>character varying</type>,
|
|
and <type>text</type>. Except where noted, these functions and operators
|
|
are declared to accept and return type <type>text</type>. They will
|
|
interchangeably accept <type>character varying</type> arguments.
|
|
Values of type <type>character</type> will be converted
|
|
to <type>text</type> before the function or operator is applied, resulting
|
|
in stripping any trailing spaces in the <type>character</type> value.
|
|
</para>
|
|
|
|
<para>
|
|
<acronym>SQL</acronym> defines some string functions that use
|
|
key words, rather than commas, to separate
|
|
arguments. Details are in
|
|
<xref linkend="functions-string-sql"/>.
|
|
<productname>PostgreSQL</productname> also provides versions of these functions
|
|
that use the regular function invocation syntax
|
|
(see <xref linkend="functions-string-other"/>).
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
The string concatenation operator (<literal>||</literal>) will accept
|
|
non-string input, so long as at least one input is of string type, as shown
|
|
in <xref linkend="functions-string-sql"/>. For other cases, inserting an
|
|
explicit coercion to <type>text</type> can be used to have non-string input
|
|
accepted.
|
|
</para>
|
|
</note>
|
|
|
|
<table id="functions-string-sql">
|
|
<title><acronym>SQL</acronym> String Functions and Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function/Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>character string</primary>
|
|
<secondary>concatenation</secondary>
|
|
</indexterm>
|
|
<type>text</type> <literal>||</literal> <type>text</type>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates the two strings.
|
|
</para>
|
|
<para>
|
|
<literal>'Post' || 'greSQL'</literal>
|
|
<returnvalue>PostgreSQL</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>text</type> <literal>||</literal> <type>anynonarray</type>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>anynonarray</type> <literal>||</literal> <type>text</type>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the non-string input to text, then concatenates the two
|
|
strings. (The non-string input cannot be of an array type, because
|
|
that would create ambiguity with the array <literal>||</literal>
|
|
operators. If you want to concatenate an array's text equivalent,
|
|
cast it to <type>text</type> explicitly.)
|
|
</para>
|
|
<para>
|
|
<literal>'Value: ' || 42</literal>
|
|
<returnvalue>Value: 42</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>btrim</primary>
|
|
</indexterm>
|
|
<function>btrim</function> ( <parameter>string</parameter> <type>text</type>
|
|
<optional>, <parameter>characters</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes the longest string containing only characters
|
|
in <parameter>characters</parameter> (a space by default)
|
|
from the start and end of <parameter>string</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>btrim('xyxtrimyyx', 'xyz')</literal>
|
|
<returnvalue>trim</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>normalized</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>Unicode normalization</primary>
|
|
</indexterm>
|
|
<type>text</type> <literal>IS</literal> <optional><literal>NOT</literal></optional> <optional><parameter>form</parameter></optional> <literal>NORMALIZED</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Checks whether the string is in the specified Unicode normalization
|
|
form. The optional <parameter>form</parameter> key word specifies the
|
|
form: <literal>NFC</literal> (the default), <literal>NFD</literal>,
|
|
<literal>NFKC</literal>, or <literal>NFKD</literal>. This expression can
|
|
only be used when the server encoding is <literal>UTF8</literal>. Note
|
|
that checking for normalization using this expression is often faster
|
|
than normalizing possibly already normalized strings.
|
|
</para>
|
|
<para>
|
|
<literal>U&'\0061\0308bc' IS NFD NORMALIZED</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bit_length</primary>
|
|
</indexterm>
|
|
<function>bit_length</function> ( <type>text</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns number of bits in the string (8
|
|
times the <function>octet_length</function>).
|
|
</para>
|
|
<para>
|
|
<literal>bit_length('jose')</literal>
|
|
<returnvalue>32</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>char_length</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>character string</primary>
|
|
<secondary>length</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>length</primary>
|
|
<secondary sortas="character string">of a character string</secondary>
|
|
<see>character string, length</see>
|
|
</indexterm>
|
|
<function>char_length</function> ( <type>text</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>character_length</primary>
|
|
</indexterm>
|
|
<function>character_length</function> ( <type>text</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns number of characters in the string.
|
|
</para>
|
|
<para>
|
|
<literal>char_length('josé')</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lower</primary>
|
|
</indexterm>
|
|
<function>lower</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the string to all lower case, according to the rules of the
|
|
database's locale.
|
|
</para>
|
|
<para>
|
|
<literal>lower('TOM')</literal>
|
|
<returnvalue>tom</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lpad</primary>
|
|
</indexterm>
|
|
<function>lpad</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>length</parameter> <type>integer</type>
|
|
<optional>, <parameter>fill</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extends the <parameter>string</parameter> to length
|
|
<parameter>length</parameter> by prepending the characters
|
|
<parameter>fill</parameter> (a space by default). If the
|
|
<parameter>string</parameter> is already longer than
|
|
<parameter>length</parameter> then it is truncated (on the right).
|
|
</para>
|
|
<para>
|
|
<literal>lpad('hi', 5, 'xy')</literal>
|
|
<returnvalue>xyxhi</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ltrim</primary>
|
|
</indexterm>
|
|
<function>ltrim</function> ( <parameter>string</parameter> <type>text</type>
|
|
<optional>, <parameter>characters</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes the longest string containing only characters in
|
|
<parameter>characters</parameter> (a space by default) from the start of
|
|
<parameter>string</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>ltrim('zzzytest', 'xyz')</literal>
|
|
<returnvalue>test</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>normalize</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>Unicode normalization</primary>
|
|
</indexterm>
|
|
<function>normalize</function> ( <type>text</type>
|
|
<optional>, <parameter>form</parameter> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the string to the specified Unicode
|
|
normalization form. The optional <parameter>form</parameter> key word
|
|
specifies the form: <literal>NFC</literal> (the default),
|
|
<literal>NFD</literal>, <literal>NFKC</literal>, or
|
|
<literal>NFKD</literal>. This function can only be used when the
|
|
server encoding is <literal>UTF8</literal>.
|
|
</para>
|
|
<para>
|
|
<literal>normalize(U&'\0061\0308bc', NFC)</literal>
|
|
<returnvalue>U&'\00E4bc'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>octet_length</primary>
|
|
</indexterm>
|
|
<function>octet_length</function> ( <type>text</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns number of bytes in the string.
|
|
</para>
|
|
<para>
|
|
<literal>octet_length('josé')</literal>
|
|
<returnvalue>5</returnvalue> (if server encoding is UTF8)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>octet_length</primary>
|
|
</indexterm>
|
|
<function>octet_length</function> ( <type>character</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns number of bytes in the string. Since this version of the
|
|
function accepts type <type>character</type> directly, it will not
|
|
strip trailing spaces.
|
|
</para>
|
|
<para>
|
|
<literal>octet_length('abc '::character(4))</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>overlay</primary>
|
|
</indexterm>
|
|
<function>overlay</function> ( <parameter>string</parameter> <type>text</type> <literal>PLACING</literal> <parameter>newsubstring</parameter> <type>text</type> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces the substring of <parameter>string</parameter> that starts at
|
|
the <parameter>start</parameter>'th character and extends
|
|
for <parameter>count</parameter> characters
|
|
with <parameter>newsubstring</parameter>.
|
|
If <parameter>count</parameter> is omitted, it defaults to the length
|
|
of <parameter>newsubstring</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>overlay('Txxxxas' placing 'hom' from 2 for 4)</literal>
|
|
<returnvalue>Thomas</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>position</primary>
|
|
</indexterm>
|
|
<function>position</function> ( <parameter>substring</parameter> <type>text</type> <literal>IN</literal> <parameter>string</parameter> <type>text</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns first starting index of the specified
|
|
<parameter>substring</parameter> within
|
|
<parameter>string</parameter>, or zero if it's not present.
|
|
</para>
|
|
<para>
|
|
<literal>position('om' in 'Thomas')</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>rpad</primary>
|
|
</indexterm>
|
|
<function>rpad</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>length</parameter> <type>integer</type>
|
|
<optional>, <parameter>fill</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extends the <parameter>string</parameter> to length
|
|
<parameter>length</parameter> by appending the characters
|
|
<parameter>fill</parameter> (a space by default). If the
|
|
<parameter>string</parameter> is already longer than
|
|
<parameter>length</parameter> then it is truncated.
|
|
</para>
|
|
<para>
|
|
<literal>rpad('hi', 5, 'xy')</literal>
|
|
<returnvalue>hixyx</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>rtrim</primary>
|
|
</indexterm>
|
|
<function>rtrim</function> ( <parameter>string</parameter> <type>text</type>
|
|
<optional>, <parameter>characters</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes the longest string containing only characters in
|
|
<parameter>characters</parameter> (a space by default) from the end of
|
|
<parameter>string</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>rtrim('testxxzx', 'xyz')</literal>
|
|
<returnvalue>test</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>substring</primary>
|
|
</indexterm>
|
|
<function>substring</function> ( <parameter>string</parameter> <type>text</type> <optional> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> </optional> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the substring of <parameter>string</parameter> starting at
|
|
the <parameter>start</parameter>'th character if that is specified,
|
|
and stopping after <parameter>count</parameter> characters if that is
|
|
specified. Provide at least one of <parameter>start</parameter>
|
|
and <parameter>count</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>substring('Thomas' from 2 for 3)</literal>
|
|
<returnvalue>hom</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>substring('Thomas' from 3)</literal>
|
|
<returnvalue>omas</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>substring('Thomas' for 2)</literal>
|
|
<returnvalue>Th</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>substring</function> ( <parameter>string</parameter> <type>text</type> <literal>FROM</literal> <parameter>pattern</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the first substring matching POSIX regular expression; see
|
|
<xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>substring('Thomas' from '...$')</literal>
|
|
<returnvalue>mas</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>substring</function> ( <parameter>string</parameter> <type>text</type> <literal>SIMILAR</literal> <parameter>pattern</parameter> <type>text</type> <literal>ESCAPE</literal> <parameter>escape</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>substring</function> ( <parameter>string</parameter> <type>text</type> <literal>FROM</literal> <parameter>pattern</parameter> <type>text</type> <literal>FOR</literal> <parameter>escape</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the first substring matching <acronym>SQL</acronym> regular expression;
|
|
see <xref linkend="functions-similarto-regexp"/>. The first form has
|
|
been specified since SQL:2003; the second form was only in SQL:1999
|
|
and should be considered obsolete.
|
|
</para>
|
|
<para>
|
|
<literal>substring('Thomas' similar '%#"o_a#"_' escape '#')</literal>
|
|
<returnvalue>oma</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>trim</primary>
|
|
</indexterm>
|
|
<function>trim</function> ( <optional> <literal>LEADING</literal> | <literal>TRAILING</literal> | <literal>BOTH</literal> </optional>
|
|
<optional> <parameter>characters</parameter> <type>text</type> </optional> <literal>FROM</literal>
|
|
<parameter>string</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes the longest string containing only characters in
|
|
<parameter>characters</parameter> (a space by default) from the
|
|
start, end, or both ends (<literal>BOTH</literal> is the default)
|
|
of <parameter>string</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>trim(both 'xyz' from 'yxTomxx')</literal>
|
|
<returnvalue>Tom</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>trim</function> ( <optional> <literal>LEADING</literal> | <literal>TRAILING</literal> | <literal>BOTH</literal> </optional> <optional> <literal>FROM</literal> </optional>
|
|
<parameter>string</parameter> <type>text</type> <optional>,
|
|
<parameter>characters</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
This is a non-standard syntax for <function>trim()</function>.
|
|
</para>
|
|
<para>
|
|
<literal>trim(both from 'yxTomxx', 'xyz')</literal>
|
|
<returnvalue>Tom</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>unicode_assigned</primary>
|
|
</indexterm>
|
|
<function>unicode_assigned</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns <literal>true</literal> if all characters in the string are
|
|
assigned Unicode codepoints; <literal>false</literal> otherwise. This
|
|
function can only be used when the server encoding is
|
|
<literal>UTF8</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>upper</primary>
|
|
</indexterm>
|
|
<function>upper</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the string to all upper case, according to the rules of the
|
|
database's locale.
|
|
</para>
|
|
<para>
|
|
<literal>upper('tom')</literal>
|
|
<returnvalue>TOM</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Additional string manipulation functions and operators are available
|
|
and are listed in <xref linkend="functions-string-other"/>. (Some of
|
|
these are used internally to implement
|
|
the <acronym>SQL</acronym>-standard string functions listed in
|
|
<xref linkend="functions-string-sql"/>.)
|
|
There are also pattern-matching operators, which are described in
|
|
<xref linkend="functions-matching"/>, and operators for full-text
|
|
search, which are described in <xref linkend="textsearch"/>.
|
|
</para>
|
|
|
|
<table id="functions-string-other">
|
|
<title>Other String Functions and Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function/Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>character string</primary>
|
|
<secondary>prefix test</secondary>
|
|
</indexterm>
|
|
<type>text</type> <literal>^@</literal> <type>text</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns true if the first string starts with the second string
|
|
(equivalent to the <function>starts_with()</function> function).
|
|
</para>
|
|
<para>
|
|
<literal>'alphabet' ^@ 'alph'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ascii</primary>
|
|
</indexterm>
|
|
<function>ascii</function> ( <type>text</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the numeric code of the first character of the argument.
|
|
In <acronym>UTF8</acronym> encoding, returns the Unicode code point
|
|
of the character. In other multibyte encodings, the argument must
|
|
be an <acronym>ASCII</acronym> character.
|
|
</para>
|
|
<para>
|
|
<literal>ascii('x')</literal>
|
|
<returnvalue>120</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>chr</primary>
|
|
</indexterm>
|
|
<function>chr</function> ( <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the character with the given code. In <acronym>UTF8</acronym>
|
|
encoding the argument is treated as a Unicode code point. In other
|
|
multibyte encodings the argument must designate
|
|
an <acronym>ASCII</acronym> character. <literal>chr(0)</literal> is
|
|
disallowed because text data types cannot store that character.
|
|
</para>
|
|
<para>
|
|
<literal>chr(65)</literal>
|
|
<returnvalue>A</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>concat</primary>
|
|
</indexterm>
|
|
<function>concat</function> ( <parameter>val1</parameter> <type>"any"</type>
|
|
[, <parameter>val2</parameter> <type>"any"</type> [, ...] ] )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates the text representations of all the arguments.
|
|
NULL arguments are ignored.
|
|
</para>
|
|
<para>
|
|
<literal>concat('abcde', 2, NULL, 22)</literal>
|
|
<returnvalue>abcde222</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>concat_ws</primary>
|
|
</indexterm>
|
|
<function>concat_ws</function> ( <parameter>sep</parameter> <type>text</type>,
|
|
<parameter>val1</parameter> <type>"any"</type>
|
|
[, <parameter>val2</parameter> <type>"any"</type> [, ...] ] )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates all but the first argument, with separators. The first
|
|
argument is used as the separator string, and should not be NULL.
|
|
Other NULL arguments are ignored.
|
|
</para>
|
|
<para>
|
|
<literal>concat_ws(',', 'abcde', 2, NULL, 22)</literal>
|
|
<returnvalue>abcde,2,22</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>format</primary>
|
|
</indexterm>
|
|
<function>format</function> ( <parameter>formatstr</parameter> <type>text</type>
|
|
[, <parameter>formatarg</parameter> <type>"any"</type> [, ...] ] )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Formats arguments according to a format string;
|
|
see <xref linkend="functions-string-format"/>.
|
|
This function is similar to the C function <function>sprintf</function>.
|
|
</para>
|
|
<para>
|
|
<literal>format('Hello %s, %1$s', 'World')</literal>
|
|
<returnvalue>Hello World, World</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>initcap</primary>
|
|
</indexterm>
|
|
<function>initcap</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the first letter of each word to upper case and the
|
|
rest to lower case. Words are sequences of alphanumeric
|
|
characters separated by non-alphanumeric characters.
|
|
</para>
|
|
<para>
|
|
<literal>initcap('hi THOMAS')</literal>
|
|
<returnvalue>Hi Thomas</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>left</primary>
|
|
</indexterm>
|
|
<function>left</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>n</parameter> <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns first <parameter>n</parameter> characters in the
|
|
string, or when <parameter>n</parameter> is negative, returns
|
|
all but last |<parameter>n</parameter>| characters.
|
|
</para>
|
|
<para>
|
|
<literal>left('abcde', 2)</literal>
|
|
<returnvalue>ab</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>length</primary>
|
|
</indexterm>
|
|
<function>length</function> ( <type>text</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of characters in the string.
|
|
</para>
|
|
<para>
|
|
<literal>length('jose')</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>md5</primary>
|
|
</indexterm>
|
|
<function>md5</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the MD5 <link linkend="functions-hash-note">hash</link> of
|
|
the argument, with the result written in hexadecimal.
|
|
</para>
|
|
<para>
|
|
<literal>md5('abc')</literal>
|
|
<returnvalue>900150983cd24fb0&zwsp;d6963f7d28e17f72</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>parse_ident</primary>
|
|
</indexterm>
|
|
<function>parse_ident</function> ( <parameter>qualified_identifier</parameter> <type>text</type>
|
|
[, <parameter>strict_mode</parameter> <type>boolean</type> <literal>DEFAULT</literal> <literal>true</literal> ] )
|
|
<returnvalue>text[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Splits <parameter>qualified_identifier</parameter> into an array of
|
|
identifiers, removing any quoting of individual identifiers. By
|
|
default, extra characters after the last identifier are considered an
|
|
error; but if the second parameter is <literal>false</literal>, then such
|
|
extra characters are ignored. (This behavior is useful for parsing
|
|
names for objects like functions.) Note that this function does not
|
|
truncate over-length identifiers. If you want truncation you can cast
|
|
the result to <type>name[]</type>.
|
|
</para>
|
|
<para>
|
|
<literal>parse_ident('"SomeSchema".someTable')</literal>
|
|
<returnvalue>{SomeSchema,sometable}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_client_encoding</primary>
|
|
</indexterm>
|
|
<function>pg_client_encoding</function> ( )
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns current client encoding name.
|
|
</para>
|
|
<para>
|
|
<literal>pg_client_encoding()</literal>
|
|
<returnvalue>UTF8</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>quote_ident</primary>
|
|
</indexterm>
|
|
<function>quote_ident</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the given string suitably quoted to be used as an identifier
|
|
in an <acronym>SQL</acronym> statement string.
|
|
Quotes are added only if necessary (i.e., if the string contains
|
|
non-identifier characters or would be case-folded).
|
|
Embedded quotes are properly doubled.
|
|
See also <xref linkend="plpgsql-quote-literal-example"/>.
|
|
</para>
|
|
<para>
|
|
<literal>quote_ident('Foo bar')</literal>
|
|
<returnvalue>"Foo bar"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>quote_literal</primary>
|
|
</indexterm>
|
|
<function>quote_literal</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the given string suitably quoted to be used as a string literal
|
|
in an <acronym>SQL</acronym> statement string.
|
|
Embedded single-quotes and backslashes are properly doubled.
|
|
Note that <function>quote_literal</function> returns null on null
|
|
input; if the argument might be null,
|
|
<function>quote_nullable</function> is often more suitable.
|
|
See also <xref linkend="plpgsql-quote-literal-example"/>.
|
|
</para>
|
|
<para>
|
|
<literal>quote_literal(E'O\'Reilly')</literal>
|
|
<returnvalue>'O''Reilly'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>quote_literal</function> ( <type>anyelement</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the given value to text and then quotes it as a literal.
|
|
Embedded single-quotes and backslashes are properly doubled.
|
|
</para>
|
|
<para>
|
|
<literal>quote_literal(42.5)</literal>
|
|
<returnvalue>'42.5'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>quote_nullable</primary>
|
|
</indexterm>
|
|
<function>quote_nullable</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the given string suitably quoted to be used as a string literal
|
|
in an <acronym>SQL</acronym> statement string; or, if the argument
|
|
is null, returns <literal>NULL</literal>.
|
|
Embedded single-quotes and backslashes are properly doubled.
|
|
See also <xref linkend="plpgsql-quote-literal-example"/>.
|
|
</para>
|
|
<para>
|
|
<literal>quote_nullable(NULL)</literal>
|
|
<returnvalue>NULL</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>quote_nullable</function> ( <type>anyelement</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the given value to text and then quotes it as a literal;
|
|
or, if the argument is null, returns <literal>NULL</literal>.
|
|
Embedded single-quotes and backslashes are properly doubled.
|
|
</para>
|
|
<para>
|
|
<literal>quote_nullable(42.5)</literal>
|
|
<returnvalue>'42.5'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regexp_count</primary>
|
|
</indexterm>
|
|
<function>regexp_count</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>
|
|
[, <parameter>start</parameter> <type>integer</type>
|
|
[, <parameter>flags</parameter> <type>text</type> ] ] )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of times the POSIX regular
|
|
expression <parameter>pattern</parameter> matches in
|
|
the <parameter>string</parameter>; see
|
|
<xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_count('123456789012', '\d\d\d', 2)</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regexp_instr</primary>
|
|
</indexterm>
|
|
<function>regexp_instr</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>
|
|
[, <parameter>start</parameter> <type>integer</type>
|
|
[, <parameter>N</parameter> <type>integer</type>
|
|
[, <parameter>endoption</parameter> <type>integer</type>
|
|
[, <parameter>flags</parameter> <type>text</type>
|
|
[, <parameter>subexpr</parameter> <type>integer</type> ] ] ] ] ] )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the position within <parameter>string</parameter> where
|
|
the <parameter>N</parameter>'th match of the POSIX regular
|
|
expression <parameter>pattern</parameter> occurs, or zero if there is
|
|
no such match; see <xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_instr('ABCDEF', 'c(.)(..)', 1, 1, 0, 'i')</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>regexp_instr('ABCDEF', 'c(.)(..)', 1, 1, 0, 'i', 2)</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regexp_like</primary>
|
|
</indexterm>
|
|
<function>regexp_like</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>
|
|
[, <parameter>flags</parameter> <type>text</type> ] )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Checks whether a match of the POSIX regular
|
|
expression <parameter>pattern</parameter> occurs
|
|
within <parameter>string</parameter>; see
|
|
<xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_like('Hello World', 'world$', 'i')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regexp_match</primary>
|
|
</indexterm>
|
|
<function>regexp_match</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> [, <parameter>flags</parameter> <type>text</type> ] )
|
|
<returnvalue>text[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns substrings within the first match of the POSIX regular
|
|
expression <parameter>pattern</parameter> to
|
|
the <parameter>string</parameter>; see
|
|
<xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_match('foobarbequebaz', '(bar)(beque)')</literal>
|
|
<returnvalue>{bar,beque}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regexp_matches</primary>
|
|
</indexterm>
|
|
<function>regexp_matches</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> [, <parameter>flags</parameter> <type>text</type> ] )
|
|
<returnvalue>setof text[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns substrings within the first match of the POSIX regular
|
|
expression <parameter>pattern</parameter> to
|
|
the <parameter>string</parameter>, or substrings within all
|
|
such matches if the <literal>g</literal> flag is used;
|
|
see <xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_matches('foobarbequebaz', 'ba.', 'g')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
{bar}
|
|
{baz}
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regexp_replace</primary>
|
|
</indexterm>
|
|
<function>regexp_replace</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>, <parameter>replacement</parameter> <type>text</type>
|
|
[, <parameter>start</parameter> <type>integer</type> ]
|
|
[, <parameter>flags</parameter> <type>text</type> ] )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces the substring that is the first match to the POSIX
|
|
regular expression <parameter>pattern</parameter>, or all such
|
|
matches if the <literal>g</literal> flag is used; see
|
|
<xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_replace('Thomas', '.[mN]a.', 'M')</literal>
|
|
<returnvalue>ThM</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>regexp_replace</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>, <parameter>replacement</parameter> <type>text</type>,
|
|
<parameter>start</parameter> <type>integer</type>,
|
|
<parameter>N</parameter> <type>integer</type>
|
|
[, <parameter>flags</parameter> <type>text</type> ] )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces the substring that is the <parameter>N</parameter>'th
|
|
match to the POSIX regular expression <parameter>pattern</parameter>,
|
|
or all such matches if <parameter>N</parameter> is zero; see
|
|
<xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_replace('Thomas', '.', 'X', 3, 2)</literal>
|
|
<returnvalue>ThoXas</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regexp_split_to_array</primary>
|
|
</indexterm>
|
|
<function>regexp_split_to_array</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> [, <parameter>flags</parameter> <type>text</type> ] )
|
|
<returnvalue>text[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Splits <parameter>string</parameter> using a POSIX regular
|
|
expression as the delimiter, producing an array of results; see
|
|
<xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_split_to_array('hello world', '\s+')</literal>
|
|
<returnvalue>{hello,world}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regexp_split_to_table</primary>
|
|
</indexterm>
|
|
<function>regexp_split_to_table</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> [, <parameter>flags</parameter> <type>text</type> ] )
|
|
<returnvalue>setof text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Splits <parameter>string</parameter> using a POSIX regular
|
|
expression as the delimiter, producing a set of results; see
|
|
<xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_split_to_table('hello world', '\s+')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
hello
|
|
world
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regexp_substr</primary>
|
|
</indexterm>
|
|
<function>regexp_substr</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>
|
|
[, <parameter>start</parameter> <type>integer</type>
|
|
[, <parameter>N</parameter> <type>integer</type>
|
|
[, <parameter>flags</parameter> <type>text</type>
|
|
[, <parameter>subexpr</parameter> <type>integer</type> ] ] ] ] )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the substring within <parameter>string</parameter> that
|
|
matches the <parameter>N</parameter>'th occurrence of the POSIX
|
|
regular expression <parameter>pattern</parameter>,
|
|
or <literal>NULL</literal> if there is no such match; see
|
|
<xref linkend="functions-posix-regexp"/>.
|
|
</para>
|
|
<para>
|
|
<literal>regexp_substr('ABCDEF', 'c(.)(..)', 1, 1, 'i')</literal>
|
|
<returnvalue>CDEF</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>regexp_substr('ABCDEF', 'c(.)(..)', 1, 1, 'i', 2)</literal>
|
|
<returnvalue>EF</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>repeat</primary>
|
|
</indexterm>
|
|
<function>repeat</function> ( <parameter>string</parameter> <type>text</type>, <parameter>number</parameter> <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Repeats <parameter>string</parameter> the specified
|
|
<parameter>number</parameter> of times.
|
|
</para>
|
|
<para>
|
|
<literal>repeat('Pg', 4)</literal>
|
|
<returnvalue>PgPgPgPg</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>replace</primary>
|
|
</indexterm>
|
|
<function>replace</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>from</parameter> <type>text</type>,
|
|
<parameter>to</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces all occurrences in <parameter>string</parameter> of
|
|
substring <parameter>from</parameter> with
|
|
substring <parameter>to</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>replace('abcdefabcdef', 'cd', 'XX')</literal>
|
|
<returnvalue>abXXefabXXef</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>reverse</primary>
|
|
</indexterm>
|
|
<function>reverse</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reverses the order of the characters in the string.
|
|
</para>
|
|
<para>
|
|
<literal>reverse('abcde')</literal>
|
|
<returnvalue>edcba</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>right</primary>
|
|
</indexterm>
|
|
<function>right</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>n</parameter> <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns last <parameter>n</parameter> characters in the string,
|
|
or when <parameter>n</parameter> is negative, returns all but
|
|
first |<parameter>n</parameter>| characters.
|
|
</para>
|
|
<para>
|
|
<literal>right('abcde', 2)</literal>
|
|
<returnvalue>de</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>split_part</primary>
|
|
</indexterm>
|
|
<function>split_part</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>delimiter</parameter> <type>text</type>,
|
|
<parameter>n</parameter> <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Splits <parameter>string</parameter> at occurrences
|
|
of <parameter>delimiter</parameter> and returns
|
|
the <parameter>n</parameter>'th field (counting from one),
|
|
or when <parameter>n</parameter> is negative, returns
|
|
the |<parameter>n</parameter>|'th-from-last field.
|
|
</para>
|
|
<para>
|
|
<literal>split_part('abc~@~def~@~ghi', '~@~', 2)</literal>
|
|
<returnvalue>def</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>split_part('abc,def,ghi,jkl', ',', -2)</literal>
|
|
<returnvalue>ghi</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>starts_with</primary>
|
|
</indexterm>
|
|
<function>starts_with</function> ( <parameter>string</parameter> <type>text</type>, <parameter>prefix</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns true if <parameter>string</parameter> starts
|
|
with <parameter>prefix</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>starts_with('alphabet', 'alph')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm id="function-string-to-array">
|
|
<primary>string_to_array</primary>
|
|
</indexterm>
|
|
<function>string_to_array</function> ( <parameter>string</parameter> <type>text</type>, <parameter>delimiter</parameter> <type>text</type> <optional>, <parameter>null_string</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Splits the <parameter>string</parameter> at occurrences
|
|
of <parameter>delimiter</parameter> and forms the resulting fields
|
|
into a <type>text</type> array.
|
|
If <parameter>delimiter</parameter> is <literal>NULL</literal>,
|
|
each character in the <parameter>string</parameter> will become a
|
|
separate element in the array.
|
|
If <parameter>delimiter</parameter> is an empty string, then
|
|
the <parameter>string</parameter> is treated as a single field.
|
|
If <parameter>null_string</parameter> is supplied and is
|
|
not <literal>NULL</literal>, fields matching that string are
|
|
replaced by <literal>NULL</literal>.
|
|
See also <link linkend="function-array-to-string"><function>array_to_string</function></link>.
|
|
</para>
|
|
<para>
|
|
<literal>string_to_array('xx~~yy~~zz', '~~', 'yy')</literal>
|
|
<returnvalue>{xx,NULL,zz}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>string_to_table</primary>
|
|
</indexterm>
|
|
<function>string_to_table</function> ( <parameter>string</parameter> <type>text</type>, <parameter>delimiter</parameter> <type>text</type> <optional>, <parameter>null_string</parameter> <type>text</type> </optional> )
|
|
<returnvalue>setof text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Splits the <parameter>string</parameter> at occurrences
|
|
of <parameter>delimiter</parameter> and returns the resulting fields
|
|
as a set of <type>text</type> rows.
|
|
If <parameter>delimiter</parameter> is <literal>NULL</literal>,
|
|
each character in the <parameter>string</parameter> will become a
|
|
separate row of the result.
|
|
If <parameter>delimiter</parameter> is an empty string, then
|
|
the <parameter>string</parameter> is treated as a single field.
|
|
If <parameter>null_string</parameter> is supplied and is
|
|
not <literal>NULL</literal>, fields matching that string are
|
|
replaced by <literal>NULL</literal>.
|
|
</para>
|
|
<para>
|
|
<literal>string_to_table('xx~^~yy~^~zz', '~^~', 'yy')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
xx
|
|
NULL
|
|
zz
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>strpos</primary>
|
|
</indexterm>
|
|
<function>strpos</function> ( <parameter>string</parameter> <type>text</type>, <parameter>substring</parameter> <type>text</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns first starting index of the specified <parameter>substring</parameter>
|
|
within <parameter>string</parameter>, or zero if it's not present.
|
|
(Same as <literal>position(<parameter>substring</parameter> in
|
|
<parameter>string</parameter>)</literal>, but note the reversed
|
|
argument order.)
|
|
</para>
|
|
<para>
|
|
<literal>strpos('high', 'ig')</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>substr</primary>
|
|
</indexterm>
|
|
<function>substr</function> ( <parameter>string</parameter> <type>text</type>, <parameter>start</parameter> <type>integer</type> <optional>, <parameter>count</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the substring of <parameter>string</parameter> starting at
|
|
the <parameter>start</parameter>'th character,
|
|
and extending for <parameter>count</parameter> characters if that is
|
|
specified. (Same
|
|
as <literal>substring(<parameter>string</parameter>
|
|
from <parameter>start</parameter>
|
|
for <parameter>count</parameter>)</literal>.)
|
|
</para>
|
|
<para>
|
|
<literal>substr('alphabet', 3)</literal>
|
|
<returnvalue>phabet</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>substr('alphabet', 3, 2)</literal>
|
|
<returnvalue>ph</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_ascii</primary>
|
|
</indexterm>
|
|
<function>to_ascii</function> ( <parameter>string</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>to_ascii</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>encoding</parameter> <type>name</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>to_ascii</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>encoding</parameter> <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts <parameter>string</parameter> to <acronym>ASCII</acronym>
|
|
from another encoding, which may be identified by name or number.
|
|
If <parameter>encoding</parameter> is omitted the database encoding
|
|
is assumed (which in practice is the only useful case).
|
|
The conversion consists primarily of dropping accents.
|
|
Conversion is only supported
|
|
from <literal>LATIN1</literal>, <literal>LATIN2</literal>,
|
|
<literal>LATIN9</literal>, and <literal>WIN1250</literal> encodings.
|
|
(See the <xref linkend="unaccent"/> module for another, more flexible
|
|
solution.)
|
|
</para>
|
|
<para>
|
|
<literal>to_ascii('Karél')</literal>
|
|
<returnvalue>Karel</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_bin</primary>
|
|
</indexterm>
|
|
<function>to_bin</function> ( <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>to_bin</function> ( <type>bigint</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the number to its equivalent two's complement binary
|
|
representation.
|
|
</para>
|
|
<para>
|
|
<literal>to_bin(2147483647)</literal>
|
|
<returnvalue>1111111111111111111111111111111</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>to_bin(-1234)</literal>
|
|
<returnvalue>11111111111111111111101100101110</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_hex</primary>
|
|
</indexterm>
|
|
<function>to_hex</function> ( <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>to_hex</function> ( <type>bigint</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the number to its equivalent two's complement hexadecimal
|
|
representation.
|
|
</para>
|
|
<para>
|
|
<literal>to_hex(2147483647)</literal>
|
|
<returnvalue>7fffffff</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>to_hex(-1234)</literal>
|
|
<returnvalue>fffffb2e</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_oct</primary>
|
|
</indexterm>
|
|
<function>to_oct</function> ( <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>to_oct</function> ( <type>bigint</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the number to its equivalent two's complement octal
|
|
representation.
|
|
</para>
|
|
<para>
|
|
<literal>to_oct(2147483647)</literal>
|
|
<returnvalue>17777777777</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>to_oct(-1234)</literal>
|
|
<returnvalue>37777775456</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>translate</primary>
|
|
</indexterm>
|
|
<function>translate</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>from</parameter> <type>text</type>,
|
|
<parameter>to</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces each character in <parameter>string</parameter> that
|
|
matches a character in the <parameter>from</parameter> set with the
|
|
corresponding character in the <parameter>to</parameter>
|
|
set. If <parameter>from</parameter> is longer than
|
|
<parameter>to</parameter>, occurrences of the extra characters in
|
|
<parameter>from</parameter> are deleted.
|
|
</para>
|
|
<para>
|
|
<literal>translate('12345', '143', 'ax')</literal>
|
|
<returnvalue>a2x5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>unistr</primary>
|
|
</indexterm>
|
|
<function>unistr</function> ( <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Evaluate escaped Unicode characters in the argument. Unicode characters
|
|
can be specified as
|
|
<literal>\<replaceable>XXXX</replaceable></literal> (4 hexadecimal
|
|
digits), <literal>\+<replaceable>XXXXXX</replaceable></literal> (6
|
|
hexadecimal digits),
|
|
<literal>\u<replaceable>XXXX</replaceable></literal> (4 hexadecimal
|
|
digits), or <literal>\U<replaceable>XXXXXXXX</replaceable></literal>
|
|
(8 hexadecimal digits). To specify a backslash, write two
|
|
backslashes. All other characters are taken literally.
|
|
</para>
|
|
|
|
<para>
|
|
If the server encoding is not UTF-8, the Unicode code point identified
|
|
by one of these escape sequences is converted to the actual server
|
|
encoding; an error is reported if that's not possible.
|
|
</para>
|
|
|
|
<para>
|
|
This function provides a (non-standard) alternative to string
|
|
constants with Unicode escapes (see <xref
|
|
linkend="sql-syntax-strings-uescape"/>).
|
|
</para>
|
|
|
|
<para>
|
|
<literal>unistr('d\0061t\+000061')</literal>
|
|
<returnvalue>data</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>unistr('d\u0061t\U00000061')</literal>
|
|
<returnvalue>data</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The <function>concat</function>, <function>concat_ws</function> and
|
|
<function>format</function> functions are variadic, so it is possible to
|
|
pass the values to be concatenated or formatted as an array marked with
|
|
the <literal>VARIADIC</literal> keyword (see <xref
|
|
linkend="xfunc-sql-variadic-functions"/>). The array's elements are
|
|
treated as if they were separate ordinary arguments to the function.
|
|
If the variadic array argument is NULL, <function>concat</function>
|
|
and <function>concat_ws</function> return NULL, but
|
|
<function>format</function> treats a NULL as a zero-element array.
|
|
</para>
|
|
|
|
<para>
|
|
See also the aggregate function <function>string_agg</function> in
|
|
<xref linkend="functions-aggregate"/>, and the functions for
|
|
converting between strings and the <type>bytea</type> type in
|
|
<xref linkend="functions-binarystring-conversions"/>.
|
|
</para>
|
|
|
|
<sect2 id="functions-string-format">
|
|
<title><function>format</function></title>
|
|
|
|
<indexterm>
|
|
<primary>format</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The function <function>format</function> produces output formatted according to
|
|
a format string, in a style similar to the C function
|
|
<function>sprintf</function>.
|
|
</para>
|
|
|
|
<para>
|
|
<synopsis>
|
|
<function>format</function>(<parameter>formatstr</parameter> <type>text</type> [, <parameter>formatarg</parameter> <type>"any"</type> [, ...] ])
|
|
</synopsis>
|
|
<parameter>formatstr</parameter> is a format string that specifies how the
|
|
result should be formatted. Text in the format string is copied
|
|
directly to the result, except where <firstterm>format specifiers</firstterm> are
|
|
used. Format specifiers act as placeholders in the string, defining how
|
|
subsequent function arguments should be formatted and inserted into the
|
|
result. Each <parameter>formatarg</parameter> argument is converted to text
|
|
according to the usual output rules for its data type, and then formatted
|
|
and inserted into the result string according to the format specifier(s).
|
|
</para>
|
|
|
|
<para>
|
|
Format specifiers are introduced by a <literal>%</literal> character and have
|
|
the form
|
|
<synopsis>
|
|
%[<parameter>position</parameter>][<parameter>flags</parameter>][<parameter>width</parameter>]<parameter>type</parameter>
|
|
</synopsis>
|
|
where the component fields are:
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><parameter>position</parameter> (optional)</term>
|
|
<listitem>
|
|
<para>
|
|
A string of the form <literal><parameter>n</parameter>$</literal> where
|
|
<parameter>n</parameter> is the index of the argument to print.
|
|
Index 1 means the first argument after
|
|
<parameter>formatstr</parameter>. If the <parameter>position</parameter> is
|
|
omitted, the default is to use the next argument in sequence.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><parameter>flags</parameter> (optional)</term>
|
|
<listitem>
|
|
<para>
|
|
Additional options controlling how the format specifier's output is
|
|
formatted. Currently the only supported flag is a minus sign
|
|
(<literal>-</literal>) which will cause the format specifier's output to be
|
|
left-justified. This has no effect unless the <parameter>width</parameter>
|
|
field is also specified.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><parameter>width</parameter> (optional)</term>
|
|
<listitem>
|
|
<para>
|
|
Specifies the <emphasis>minimum</emphasis> number of characters to use to
|
|
display the format specifier's output. The output is padded on the
|
|
left or right (depending on the <literal>-</literal> flag) with spaces as
|
|
needed to fill the width. A too-small width does not cause
|
|
truncation of the output, but is simply ignored. The width may be
|
|
specified using any of the following: a positive integer; an
|
|
asterisk (<literal>*</literal>) to use the next function argument as the
|
|
width; or a string of the form <literal>*<parameter>n</parameter>$</literal> to
|
|
use the <parameter>n</parameter>th function argument as the width.
|
|
</para>
|
|
|
|
<para>
|
|
If the width comes from a function argument, that argument is
|
|
consumed before the argument that is used for the format specifier's
|
|
value. If the width argument is negative, the result is left
|
|
aligned (as if the <literal>-</literal> flag had been specified) within a
|
|
field of length <function>abs</function>(<parameter>width</parameter>).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><parameter>type</parameter> (required)</term>
|
|
<listitem>
|
|
<para>
|
|
The type of format conversion to use to produce the format
|
|
specifier's output. The following types are supported:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
<literal>s</literal> formats the argument value as a simple
|
|
string. A null value is treated as an empty string.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>I</literal> treats the argument value as an SQL
|
|
identifier, double-quoting it if necessary.
|
|
It is an error for the value to be null (equivalent to
|
|
<function>quote_ident</function>).
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>L</literal> quotes the argument value as an SQL literal.
|
|
A null value is displayed as the string <literal>NULL</literal>, without
|
|
quotes (equivalent to <function>quote_nullable</function>).
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
|
|
<para>
|
|
In addition to the format specifiers described above, the special sequence
|
|
<literal>%%</literal> may be used to output a literal <literal>%</literal> character.
|
|
</para>
|
|
|
|
<para>
|
|
Here are some examples of the basic format conversions:
|
|
|
|
<screen>
|
|
SELECT format('Hello %s', 'World');
|
|
<lineannotation>Result: </lineannotation><computeroutput>Hello World</computeroutput>
|
|
|
|
SELECT format('Testing %s, %s, %s, %%', 'one', 'two', 'three');
|
|
<lineannotation>Result: </lineannotation><computeroutput>Testing one, two, three, %</computeroutput>
|
|
|
|
SELECT format('INSERT INTO %I VALUES(%L)', 'Foo bar', E'O\'Reilly');
|
|
<lineannotation>Result: </lineannotation><computeroutput>INSERT INTO "Foo bar" VALUES('O''Reilly')</computeroutput>
|
|
|
|
SELECT format('INSERT INTO %I VALUES(%L)', 'locations', 'C:\Program Files');
|
|
<lineannotation>Result: </lineannotation><computeroutput>INSERT INTO locations VALUES('C:\Program Files')</computeroutput>
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
Here are examples using <parameter>width</parameter> fields
|
|
and the <literal>-</literal> flag:
|
|
|
|
<screen>
|
|
SELECT format('|%10s|', 'foo');
|
|
<lineannotation>Result: </lineannotation><computeroutput>| foo|</computeroutput>
|
|
|
|
SELECT format('|%-10s|', 'foo');
|
|
<lineannotation>Result: </lineannotation><computeroutput>|foo |</computeroutput>
|
|
|
|
SELECT format('|%*s|', 10, 'foo');
|
|
<lineannotation>Result: </lineannotation><computeroutput>| foo|</computeroutput>
|
|
|
|
SELECT format('|%*s|', -10, 'foo');
|
|
<lineannotation>Result: </lineannotation><computeroutput>|foo |</computeroutput>
|
|
|
|
SELECT format('|%-*s|', 10, 'foo');
|
|
<lineannotation>Result: </lineannotation><computeroutput>|foo |</computeroutput>
|
|
|
|
SELECT format('|%-*s|', -10, 'foo');
|
|
<lineannotation>Result: </lineannotation><computeroutput>|foo |</computeroutput>
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
These examples show use of <parameter>position</parameter> fields:
|
|
|
|
<screen>
|
|
SELECT format('Testing %3$s, %2$s, %1$s', 'one', 'two', 'three');
|
|
<lineannotation>Result: </lineannotation><computeroutput>Testing three, two, one</computeroutput>
|
|
|
|
SELECT format('|%*2$s|', 'foo', 10, 'bar');
|
|
<lineannotation>Result: </lineannotation><computeroutput>| bar|</computeroutput>
|
|
|
|
SELECT format('|%1$*2$s|', 'foo', 10, 'bar');
|
|
<lineannotation>Result: </lineannotation><computeroutput>| foo|</computeroutput>
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
Unlike the standard C function <function>sprintf</function>,
|
|
<productname>PostgreSQL</productname>'s <function>format</function> function allows format
|
|
specifiers with and without <parameter>position</parameter> fields to be mixed
|
|
in the same format string. A format specifier without a
|
|
<parameter>position</parameter> field always uses the next argument after the
|
|
last argument consumed.
|
|
In addition, the <function>format</function> function does not require all
|
|
function arguments to be used in the format string.
|
|
For example:
|
|
|
|
<screen>
|
|
SELECT format('Testing %3$s, %2$s, %s', 'one', 'two', 'three');
|
|
<lineannotation>Result: </lineannotation><computeroutput>Testing three, two, three</computeroutput>
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
The <literal>%I</literal> and <literal>%L</literal> format specifiers are particularly
|
|
useful for safely constructing dynamic SQL statements. See
|
|
<xref linkend="plpgsql-quote-literal-example"/>.
|
|
</para>
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-binarystring">
|
|
<title>Binary String Functions and Operators</title>
|
|
|
|
<indexterm zone="functions-binarystring">
|
|
<primary>binary data</primary>
|
|
<secondary>functions</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
This section describes functions and operators for examining and
|
|
manipulating binary strings, that is values of type <type>bytea</type>.
|
|
Many of these are equivalent, in purpose and syntax, to the
|
|
text-string functions described in the previous section.
|
|
</para>
|
|
|
|
<para>
|
|
<acronym>SQL</acronym> defines some string functions that use
|
|
key words, rather than commas, to separate
|
|
arguments. Details are in
|
|
<xref linkend="functions-binarystring-sql"/>.
|
|
<productname>PostgreSQL</productname> also provides versions of these functions
|
|
that use the regular function invocation syntax
|
|
(see <xref linkend="functions-binarystring-other"/>).
|
|
</para>
|
|
|
|
<table id="functions-binarystring-sql">
|
|
<title><acronym>SQL</acronym> Binary String Functions and Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function/Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>binary string</primary>
|
|
<secondary>concatenation</secondary>
|
|
</indexterm>
|
|
<type>bytea</type> <literal>||</literal> <type>bytea</type>
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates the two binary strings.
|
|
</para>
|
|
<para>
|
|
<literal>'\x123456'::bytea || '\x789a00bcde'::bytea</literal>
|
|
<returnvalue>\x123456789a00bcde</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bit_length</primary>
|
|
</indexterm>
|
|
<function>bit_length</function> ( <type>bytea</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns number of bits in the binary string (8
|
|
times the <function>octet_length</function>).
|
|
</para>
|
|
<para>
|
|
<literal>bit_length('\x123456'::bytea)</literal>
|
|
<returnvalue>24</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>btrim</primary>
|
|
</indexterm>
|
|
<function>btrim</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>bytesremoved</parameter> <type>bytea</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes the longest string containing only bytes appearing in
|
|
<parameter>bytesremoved</parameter> from the start and end of
|
|
<parameter>bytes</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>btrim('\x1234567890'::bytea, '\x9012'::bytea)</literal>
|
|
<returnvalue>\x345678</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ltrim</primary>
|
|
</indexterm>
|
|
<function>ltrim</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>bytesremoved</parameter> <type>bytea</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes the longest string containing only bytes appearing in
|
|
<parameter>bytesremoved</parameter> from the start of
|
|
<parameter>bytes</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>ltrim('\x1234567890'::bytea, '\x9012'::bytea)</literal>
|
|
<returnvalue>\x34567890</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>octet_length</primary>
|
|
</indexterm>
|
|
<function>octet_length</function> ( <type>bytea</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns number of bytes in the binary string.
|
|
</para>
|
|
<para>
|
|
<literal>octet_length('\x123456'::bytea)</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>overlay</primary>
|
|
</indexterm>
|
|
<function>overlay</function> ( <parameter>bytes</parameter> <type>bytea</type> <literal>PLACING</literal> <parameter>newsubstring</parameter> <type>bytea</type> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces the substring of <parameter>bytes</parameter> that starts at
|
|
the <parameter>start</parameter>'th byte and extends
|
|
for <parameter>count</parameter> bytes
|
|
with <parameter>newsubstring</parameter>.
|
|
If <parameter>count</parameter> is omitted, it defaults to the length
|
|
of <parameter>newsubstring</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>overlay('\x1234567890'::bytea placing '\002\003'::bytea from 2 for 3)</literal>
|
|
<returnvalue>\x12020390</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>position</primary>
|
|
</indexterm>
|
|
<function>position</function> ( <parameter>substring</parameter> <type>bytea</type> <literal>IN</literal> <parameter>bytes</parameter> <type>bytea</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns first starting index of the specified
|
|
<parameter>substring</parameter> within
|
|
<parameter>bytes</parameter>, or zero if it's not present.
|
|
</para>
|
|
<para>
|
|
<literal>position('\x5678'::bytea in '\x1234567890'::bytea)</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>rtrim</primary>
|
|
</indexterm>
|
|
<function>rtrim</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>bytesremoved</parameter> <type>bytea</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes the longest string containing only bytes appearing in
|
|
<parameter>bytesremoved</parameter> from the end of
|
|
<parameter>bytes</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>rtrim('\x1234567890'::bytea, '\x9012'::bytea)</literal>
|
|
<returnvalue>\x12345678</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>substring</primary>
|
|
</indexterm>
|
|
<function>substring</function> ( <parameter>bytes</parameter> <type>bytea</type> <optional> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> </optional> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the substring of <parameter>bytes</parameter> starting at
|
|
the <parameter>start</parameter>'th byte if that is specified,
|
|
and stopping after <parameter>count</parameter> bytes if that is
|
|
specified. Provide at least one of <parameter>start</parameter>
|
|
and <parameter>count</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>substring('\x1234567890'::bytea from 3 for 2)</literal>
|
|
<returnvalue>\x5678</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>trim</primary>
|
|
</indexterm>
|
|
<function>trim</function> ( <optional> <literal>LEADING</literal> | <literal>TRAILING</literal> | <literal>BOTH</literal> </optional>
|
|
<parameter>bytesremoved</parameter> <type>bytea</type> <literal>FROM</literal>
|
|
<parameter>bytes</parameter> <type>bytea</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes the longest string containing only bytes appearing in
|
|
<parameter>bytesremoved</parameter> from the start,
|
|
end, or both ends (<literal>BOTH</literal> is the default)
|
|
of <parameter>bytes</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>trim('\x9012'::bytea from '\x1234567890'::bytea)</literal>
|
|
<returnvalue>\x345678</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>trim</function> ( <optional> <literal>LEADING</literal> | <literal>TRAILING</literal> | <literal>BOTH</literal> </optional> <optional> <literal>FROM</literal> </optional>
|
|
<parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>bytesremoved</parameter> <type>bytea</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
This is a non-standard syntax for <function>trim()</function>.
|
|
</para>
|
|
<para>
|
|
<literal>trim(both from '\x1234567890'::bytea, '\x9012'::bytea)</literal>
|
|
<returnvalue>\x345678</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Additional binary string manipulation functions are available and
|
|
are listed in <xref linkend="functions-binarystring-other"/>. Some
|
|
of them are used internally to implement the
|
|
<acronym>SQL</acronym>-standard string functions listed in <xref
|
|
linkend="functions-binarystring-sql"/>.
|
|
</para>
|
|
|
|
<table id="functions-binarystring-other">
|
|
<title>Other Binary String Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bit_count</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>popcount</primary>
|
|
<see>bit_count</see>
|
|
</indexterm>
|
|
<function>bit_count</function> ( <parameter>bytes</parameter> <type>bytea</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of bits set in the binary string (also known as
|
|
<quote>popcount</quote>).
|
|
</para>
|
|
<para>
|
|
<literal>bit_count('\x1234567890'::bytea)</literal>
|
|
<returnvalue>15</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>get_bit</primary>
|
|
</indexterm>
|
|
<function>get_bit</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>n</parameter> <type>bigint</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts <link linkend="functions-zerobased-note">n'th</link> bit
|
|
from binary string.
|
|
</para>
|
|
<para>
|
|
<literal>get_bit('\x1234567890'::bytea, 30)</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>get_byte</primary>
|
|
</indexterm>
|
|
<function>get_byte</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>n</parameter> <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts <link linkend="functions-zerobased-note">n'th</link> byte
|
|
from binary string.
|
|
</para>
|
|
<para>
|
|
<literal>get_byte('\x1234567890'::bytea, 4)</literal>
|
|
<returnvalue>144</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>length</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>binary string</primary>
|
|
<secondary>length</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>length</primary>
|
|
<secondary sortas="binary string">of a binary string</secondary>
|
|
<see>binary strings, length</see>
|
|
</indexterm>
|
|
<function>length</function> ( <type>bytea</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of bytes in the binary string.
|
|
</para>
|
|
<para>
|
|
<literal>length('\x1234567890'::bytea)</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>length</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>encoding</parameter> <type>name</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of characters in the binary string, assuming
|
|
that it is text in the given <parameter>encoding</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>length('jose'::bytea, 'UTF8')</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>md5</primary>
|
|
</indexterm>
|
|
<function>md5</function> ( <type>bytea</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the MD5 <link linkend="functions-hash-note">hash</link> of
|
|
the binary string, with the result written in hexadecimal.
|
|
</para>
|
|
<para>
|
|
<literal>md5('Th\000omas'::bytea)</literal>
|
|
<returnvalue>8ab2d3c9689aaf18&zwsp;b4958c334c82d8b1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>set_bit</primary>
|
|
</indexterm>
|
|
<function>set_bit</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>n</parameter> <type>bigint</type>,
|
|
<parameter>newvalue</parameter> <type>integer</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets <link linkend="functions-zerobased-note">n'th</link> bit in
|
|
binary string to <parameter>newvalue</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>set_bit('\x1234567890'::bytea, 30, 0)</literal>
|
|
<returnvalue>\x1234563890</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>set_byte</primary>
|
|
</indexterm>
|
|
<function>set_byte</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>n</parameter> <type>integer</type>,
|
|
<parameter>newvalue</parameter> <type>integer</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets <link linkend="functions-zerobased-note">n'th</link> byte in
|
|
binary string to <parameter>newvalue</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>set_byte('\x1234567890'::bytea, 4, 64)</literal>
|
|
<returnvalue>\x1234567840</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sha224</primary>
|
|
</indexterm>
|
|
<function>sha224</function> ( <type>bytea</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the SHA-224 <link linkend="functions-hash-note">hash</link>
|
|
of the binary string.
|
|
</para>
|
|
<para>
|
|
<literal>sha224('abc'::bytea)</literal>
|
|
<returnvalue>\x23097d223405d8228642a477bda2&zwsp;55b32aadbce4bda0b3f7e36c9da7</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sha256</primary>
|
|
</indexterm>
|
|
<function>sha256</function> ( <type>bytea</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the SHA-256 <link linkend="functions-hash-note">hash</link>
|
|
of the binary string.
|
|
</para>
|
|
<para>
|
|
<literal>sha256('abc'::bytea)</literal>
|
|
<returnvalue>\xba7816bf8f01cfea414140de5dae2223&zwsp;b00361a396177a9cb410ff61f20015ad</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sha384</primary>
|
|
</indexterm>
|
|
<function>sha384</function> ( <type>bytea</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the SHA-384 <link linkend="functions-hash-note">hash</link>
|
|
of the binary string.
|
|
</para>
|
|
<para>
|
|
<literal>sha384('abc'::bytea)</literal>
|
|
<returnvalue>\xcb00753f45a35e8bb5a03d699ac65007&zwsp;272c32ab0eded1631a8b605a43ff5bed&zwsp;8086072ba1e7cc2358baeca134c825a7</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sha512</primary>
|
|
</indexterm>
|
|
<function>sha512</function> ( <type>bytea</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the SHA-512 <link linkend="functions-hash-note">hash</link>
|
|
of the binary string.
|
|
</para>
|
|
<para>
|
|
<literal>sha512('abc'::bytea)</literal>
|
|
<returnvalue>\xddaf35a193617abacc417349ae204131&zwsp;12e6fa4e89a97ea20a9eeee64b55d39a&zwsp;2192992a274fc1a836ba3c23a3feebbd&zwsp;454d4423643ce80e2a9ac94fa54ca49f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>substr</primary>
|
|
</indexterm>
|
|
<function>substr</function> ( <parameter>bytes</parameter> <type>bytea</type>, <parameter>start</parameter> <type>integer</type> <optional>, <parameter>count</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the substring of <parameter>bytes</parameter> starting at
|
|
the <parameter>start</parameter>'th byte,
|
|
and extending for <parameter>count</parameter> bytes if that is
|
|
specified. (Same
|
|
as <literal>substring(<parameter>bytes</parameter>
|
|
from <parameter>start</parameter>
|
|
for <parameter>count</parameter>)</literal>.)
|
|
</para>
|
|
<para>
|
|
<literal>substr('\x1234567890'::bytea, 3, 2)</literal>
|
|
<returnvalue>\x5678</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para id="functions-zerobased-note">
|
|
Functions <function>get_byte</function> and <function>set_byte</function>
|
|
number the first byte of a binary string as byte 0.
|
|
Functions <function>get_bit</function> and <function>set_bit</function>
|
|
number bits from the right within each byte; for example bit 0 is the least
|
|
significant bit of the first byte, and bit 15 is the most significant bit
|
|
of the second byte.
|
|
</para>
|
|
|
|
<para id="functions-hash-note">
|
|
For historical reasons, the function <function>md5</function>
|
|
returns a hex-encoded value of type <type>text</type> whereas the SHA-2
|
|
functions return type <type>bytea</type>. Use the functions
|
|
<link linkend="function-encode"><function>encode</function></link>
|
|
and <link linkend="function-decode"><function>decode</function></link> to
|
|
convert between the two. For example write <literal>encode(sha256('abc'),
|
|
'hex')</literal> to get a hex-encoded text representation,
|
|
or <literal>decode(md5('abc'), 'hex')</literal> to get
|
|
a <type>bytea</type> value.
|
|
</para>
|
|
|
|
<para>
|
|
<indexterm>
|
|
<primary>character string</primary>
|
|
<secondary>converting to binary string</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>binary string</primary>
|
|
<secondary>converting to character string</secondary>
|
|
</indexterm>
|
|
Functions for converting strings between different character sets
|
|
(encodings), and for representing arbitrary binary data in textual
|
|
form, are shown in
|
|
<xref linkend="functions-binarystring-conversions"/>. For these
|
|
functions, an argument or result of type <type>text</type> is expressed
|
|
in the database's default encoding, while arguments or results of
|
|
type <type>bytea</type> are in an encoding named by another argument.
|
|
</para>
|
|
|
|
<table id="functions-binarystring-conversions">
|
|
<title>Text/Binary String Conversion Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>convert</primary>
|
|
</indexterm>
|
|
<function>convert</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>src_encoding</parameter> <type>name</type>,
|
|
<parameter>dest_encoding</parameter> <type>name</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts a binary string representing text in
|
|
encoding <parameter>src_encoding</parameter>
|
|
to a binary string in encoding <parameter>dest_encoding</parameter>
|
|
(see <xref linkend="multibyte-conversions-supported"/> for
|
|
available conversions).
|
|
</para>
|
|
<para>
|
|
<literal>convert('text_in_utf8', 'UTF8', 'LATIN1')</literal>
|
|
<returnvalue>\x746578745f696e5f75746638</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>convert_from</primary>
|
|
</indexterm>
|
|
<function>convert_from</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>src_encoding</parameter> <type>name</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts a binary string representing text in
|
|
encoding <parameter>src_encoding</parameter>
|
|
to <type>text</type> in the database encoding
|
|
(see <xref linkend="multibyte-conversions-supported"/> for
|
|
available conversions).
|
|
</para>
|
|
<para>
|
|
<literal>convert_from('text_in_utf8', 'UTF8')</literal>
|
|
<returnvalue>text_in_utf8</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>convert_to</primary>
|
|
</indexterm>
|
|
<function>convert_to</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>dest_encoding</parameter> <type>name</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts a <type>text</type> string (in the database encoding) to a
|
|
binary string encoded in encoding <parameter>dest_encoding</parameter>
|
|
(see <xref linkend="multibyte-conversions-supported"/> for
|
|
available conversions).
|
|
</para>
|
|
<para>
|
|
<literal>convert_to('some_text', 'UTF8')</literal>
|
|
<returnvalue>\x736f6d655f74657874</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm id="function-encode">
|
|
<primary>encode</primary>
|
|
</indexterm>
|
|
<function>encode</function> ( <parameter>bytes</parameter> <type>bytea</type>,
|
|
<parameter>format</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Encodes binary data into a textual representation; supported
|
|
<parameter>format</parameter> values are:
|
|
<link linkend="encode-format-base64"><literal>base64</literal></link>,
|
|
<link linkend="encode-format-escape"><literal>escape</literal></link>,
|
|
<link linkend="encode-format-hex"><literal>hex</literal></link>.
|
|
</para>
|
|
<para>
|
|
<literal>encode('123\000\001', 'base64')</literal>
|
|
<returnvalue>MTIzAAE=</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm id="function-decode">
|
|
<primary>decode</primary>
|
|
</indexterm>
|
|
<function>decode</function> ( <parameter>string</parameter> <type>text</type>,
|
|
<parameter>format</parameter> <type>text</type> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Decodes binary data from a textual representation; supported
|
|
<parameter>format</parameter> values are the same as
|
|
for <function>encode</function>.
|
|
</para>
|
|
<para>
|
|
<literal>decode('MTIzAAE=', 'base64')</literal>
|
|
<returnvalue>\x3132330001</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The <function>encode</function> and <function>decode</function>
|
|
functions support the following textual formats:
|
|
|
|
<variablelist>
|
|
<varlistentry id="encode-format-base64">
|
|
<term>base64
|
|
<indexterm>
|
|
<primary>base64 format</primary>
|
|
</indexterm></term>
|
|
<listitem>
|
|
<para>
|
|
The <literal>base64</literal> format is that
|
|
of <ulink url="https://datatracker.ietf.org/doc/html/rfc2045#section-6.8">RFC
|
|
2045 Section 6.8</ulink>. As per the <acronym>RFC</acronym>, encoded lines are
|
|
broken at 76 characters. However instead of the MIME CRLF
|
|
end-of-line marker, only a newline is used for end-of-line.
|
|
The <function>decode</function> function ignores carriage-return,
|
|
newline, space, and tab characters. Otherwise, an error is
|
|
raised when <function>decode</function> is supplied invalid
|
|
base64 data — including when trailing padding is incorrect.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="encode-format-escape">
|
|
<term>escape
|
|
<indexterm>
|
|
<primary>escape format</primary>
|
|
</indexterm></term>
|
|
<listitem>
|
|
<para>
|
|
The <literal>escape</literal> format converts zero bytes and
|
|
bytes with the high bit set into octal escape sequences
|
|
(<literal>\</literal><replaceable>nnn</replaceable>), and it doubles
|
|
backslashes. Other byte values are represented literally.
|
|
The <function>decode</function> function will raise an error if a
|
|
backslash is not followed by either a second backslash or three
|
|
octal digits; it accepts other byte values unchanged.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="encode-format-hex">
|
|
<term>hex
|
|
<indexterm>
|
|
<primary>hex format</primary>
|
|
</indexterm></term>
|
|
<listitem>
|
|
<para>
|
|
The <literal>hex</literal> format represents each 4 bits of
|
|
data as one hexadecimal digit, <literal>0</literal>
|
|
through <literal>f</literal>, writing the higher-order digit of
|
|
each byte first. The <function>encode</function> function outputs
|
|
the <literal>a</literal>-<literal>f</literal> hex digits in lower
|
|
case. Because the smallest unit of data is 8 bits, there are
|
|
always an even number of characters returned
|
|
by <function>encode</function>.
|
|
The <function>decode</function> function
|
|
accepts the <literal>a</literal>-<literal>f</literal> characters in
|
|
either upper or lower case. An error is raised
|
|
when <function>decode</function> is given invalid hex data
|
|
— including when given an odd number of characters.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
|
|
<para>
|
|
See also the aggregate function <function>string_agg</function> in
|
|
<xref linkend="functions-aggregate"/> and the large object functions
|
|
in <xref linkend="lo-funcs"/>.
|
|
</para>
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-bitstring">
|
|
<title>Bit String Functions and Operators</title>
|
|
|
|
<indexterm zone="functions-bitstring">
|
|
<primary>bit strings</primary>
|
|
<secondary>functions</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
This section describes functions and operators for examining and
|
|
manipulating bit strings, that is values of the types
|
|
<type>bit</type> and <type>bit varying</type>. (While only
|
|
type <type>bit</type> is mentioned in these tables, values of
|
|
type <type>bit varying</type> can be used interchangeably.)
|
|
Bit strings support the usual comparison operators shown in
|
|
<xref linkend="functions-comparison-op-table"/>, as well as the
|
|
operators shown in <xref linkend="functions-bit-string-op-table"/>.
|
|
</para>
|
|
|
|
<table id="functions-bit-string-op-table">
|
|
<title>Bit String Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>bit</type> <literal>||</literal> <type>bit</type>
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenation
|
|
</para>
|
|
<para>
|
|
<literal>B'10001' || B'011'</literal>
|
|
<returnvalue>10001011</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>bit</type> <literal>&</literal> <type>bit</type>
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise AND (inputs must be of equal length)
|
|
</para>
|
|
<para>
|
|
<literal>B'10001' & B'01101'</literal>
|
|
<returnvalue>00001</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>bit</type> <literal>|</literal> <type>bit</type>
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise OR (inputs must be of equal length)
|
|
</para>
|
|
<para>
|
|
<literal>B'10001' | B'01101'</literal>
|
|
<returnvalue>11101</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>bit</type> <literal>#</literal> <type>bit</type>
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise exclusive OR (inputs must be of equal length)
|
|
</para>
|
|
<para>
|
|
<literal>B'10001' # B'01101'</literal>
|
|
<returnvalue>11100</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>~</literal> <type>bit</type>
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise NOT
|
|
</para>
|
|
<para>
|
|
<literal>~ B'10001'</literal>
|
|
<returnvalue>01110</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>bit</type> <literal><<</literal> <type>integer</type>
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise shift left
|
|
(string length is preserved)
|
|
</para>
|
|
<para>
|
|
<literal>B'10001' << 3</literal>
|
|
<returnvalue>01000</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>bit</type> <literal>>></literal> <type>integer</type>
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Bitwise shift right
|
|
(string length is preserved)
|
|
</para>
|
|
<para>
|
|
<literal>B'10001' >> 2</literal>
|
|
<returnvalue>00100</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Some of the functions available for binary strings are also available
|
|
for bit strings, as shown in <xref linkend="functions-bit-string-table"/>.
|
|
</para>
|
|
|
|
<table id="functions-bit-string-table">
|
|
<title>Bit String Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bit_count</primary>
|
|
</indexterm>
|
|
<function>bit_count</function> ( <type>bit</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of bits set in the bit string (also known as
|
|
<quote>popcount</quote>).
|
|
</para>
|
|
<para>
|
|
<literal>bit_count(B'10111')</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bit_length</primary>
|
|
</indexterm>
|
|
<function>bit_length</function> ( <type>bit</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns number of bits in the bit string.
|
|
</para>
|
|
<para>
|
|
<literal>bit_length(B'10111')</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>length</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>bit string</primary>
|
|
<secondary>length</secondary>
|
|
</indexterm>
|
|
<function>length</function> ( <type>bit</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns number of bits in the bit string.
|
|
</para>
|
|
<para>
|
|
<literal>length(B'10111')</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>octet_length</primary>
|
|
</indexterm>
|
|
<function>octet_length</function> ( <type>bit</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns number of bytes in the bit string.
|
|
</para>
|
|
<para>
|
|
<literal>octet_length(B'1011111011')</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>overlay</primary>
|
|
</indexterm>
|
|
<function>overlay</function> ( <parameter>bits</parameter> <type>bit</type> <literal>PLACING</literal> <parameter>newsubstring</parameter> <type>bit</type> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces the substring of <parameter>bits</parameter> that starts at
|
|
the <parameter>start</parameter>'th bit and extends
|
|
for <parameter>count</parameter> bits
|
|
with <parameter>newsubstring</parameter>.
|
|
If <parameter>count</parameter> is omitted, it defaults to the length
|
|
of <parameter>newsubstring</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>overlay(B'01010101010101010' placing B'11111' from 2 for 3)</literal>
|
|
<returnvalue>0111110101010101010</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>position</primary>
|
|
</indexterm>
|
|
<function>position</function> ( <parameter>substring</parameter> <type>bit</type> <literal>IN</literal> <parameter>bits</parameter> <type>bit</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns first starting index of the specified <parameter>substring</parameter>
|
|
within <parameter>bits</parameter>, or zero if it's not present.
|
|
</para>
|
|
<para>
|
|
<literal>position(B'010' in B'000001101011')</literal>
|
|
<returnvalue>8</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>substring</primary>
|
|
</indexterm>
|
|
<function>substring</function> ( <parameter>bits</parameter> <type>bit</type> <optional> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> </optional> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the substring of <parameter>bits</parameter> starting at
|
|
the <parameter>start</parameter>'th bit if that is specified,
|
|
and stopping after <parameter>count</parameter> bits if that is
|
|
specified. Provide at least one of <parameter>start</parameter>
|
|
and <parameter>count</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>substring(B'110010111111' from 3 for 2)</literal>
|
|
<returnvalue>00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>get_bit</primary>
|
|
</indexterm>
|
|
<function>get_bit</function> ( <parameter>bits</parameter> <type>bit</type>,
|
|
<parameter>n</parameter> <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts <parameter>n</parameter>'th bit
|
|
from bit string; the first (leftmost) bit is bit 0.
|
|
</para>
|
|
<para>
|
|
<literal>get_bit(B'101010101010101010', 6)</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>set_bit</primary>
|
|
</indexterm>
|
|
<function>set_bit</function> ( <parameter>bits</parameter> <type>bit</type>,
|
|
<parameter>n</parameter> <type>integer</type>,
|
|
<parameter>newvalue</parameter> <type>integer</type> )
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets <parameter>n</parameter>'th bit in
|
|
bit string to <parameter>newvalue</parameter>;
|
|
the first (leftmost) bit is bit 0.
|
|
</para>
|
|
<para>
|
|
<literal>set_bit(B'101010101010101010', 6, 0)</literal>
|
|
<returnvalue>101010001010101010</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
In addition, it is possible to cast integral values to and from type
|
|
<type>bit</type>.
|
|
Casting an integer to <type>bit(n)</type> copies the rightmost
|
|
<literal>n</literal> bits. Casting an integer to a bit string width wider
|
|
than the integer itself will sign-extend on the left.
|
|
Some examples:
|
|
<programlisting>
|
|
44::bit(10) <lineannotation>0000101100</lineannotation>
|
|
44::bit(3) <lineannotation>100</lineannotation>
|
|
cast(-44 as bit(12)) <lineannotation>111111010100</lineannotation>
|
|
'1110'::bit(4)::integer <lineannotation>14</lineannotation>
|
|
</programlisting>
|
|
Note that casting to just <quote>bit</quote> means casting to
|
|
<literal>bit(1)</literal>, and so will deliver only the least significant
|
|
bit of the integer.
|
|
</para>
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-matching">
|
|
<title>Pattern Matching</title>
|
|
|
|
<indexterm zone="functions-matching">
|
|
<primary>pattern matching</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
There are three separate approaches to pattern matching provided
|
|
by <productname>PostgreSQL</productname>: the traditional
|
|
<acronym>SQL</acronym> <function>LIKE</function> operator, the
|
|
more recent <function>SIMILAR TO</function> operator (added in
|
|
SQL:1999), and <acronym>POSIX</acronym>-style regular
|
|
expressions. Aside from the basic <quote>does this string match
|
|
this pattern?</quote> operators, functions are available to extract
|
|
or replace matching substrings and to split a string at matching
|
|
locations.
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
If you have pattern matching needs that go beyond this,
|
|
consider writing a user-defined function in Perl or Tcl.
|
|
</para>
|
|
</tip>
|
|
|
|
<caution>
|
|
<para>
|
|
While most regular-expression searches can be executed very quickly,
|
|
regular expressions can be contrived that take arbitrary amounts of
|
|
time and memory to process. Be wary of accepting regular-expression
|
|
search patterns from hostile sources. If you must do so, it is
|
|
advisable to impose a statement timeout.
|
|
</para>
|
|
|
|
<para>
|
|
Searches using <function>SIMILAR TO</function> patterns have the same
|
|
security hazards, since <function>SIMILAR TO</function> provides many
|
|
of the same capabilities as <acronym>POSIX</acronym>-style regular
|
|
expressions.
|
|
</para>
|
|
|
|
<para>
|
|
<function>LIKE</function> searches, being much simpler than the other
|
|
two options, are safer to use with possibly-hostile pattern sources.
|
|
</para>
|
|
</caution>
|
|
|
|
<para>
|
|
The pattern matching operators of all three kinds do not support
|
|
nondeterministic collations. If required, apply a different collation to
|
|
the expression to work around this limitation.
|
|
</para>
|
|
|
|
<sect2 id="functions-like">
|
|
<title><function>LIKE</function></title>
|
|
|
|
<indexterm>
|
|
<primary>LIKE</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<replaceable>string</replaceable> LIKE <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
|
|
<replaceable>string</replaceable> NOT LIKE <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>LIKE</function> expression returns true if the
|
|
<replaceable>string</replaceable> matches the supplied
|
|
<replaceable>pattern</replaceable>. (As
|
|
expected, the <function>NOT LIKE</function> expression returns
|
|
false if <function>LIKE</function> returns true, and vice versa.
|
|
An equivalent expression is
|
|
<literal>NOT (<replaceable>string</replaceable> LIKE
|
|
<replaceable>pattern</replaceable>)</literal>.)
|
|
</para>
|
|
|
|
<para>
|
|
If <replaceable>pattern</replaceable> does not contain percent
|
|
signs or underscores, then the pattern only represents the string
|
|
itself; in that case <function>LIKE</function> acts like the
|
|
equals operator. An underscore (<literal>_</literal>) in
|
|
<replaceable>pattern</replaceable> stands for (matches) any single
|
|
character; a percent sign (<literal>%</literal>) matches any sequence
|
|
of zero or more characters.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
'abc' LIKE 'abc' <lineannotation>true</lineannotation>
|
|
'abc' LIKE 'a%' <lineannotation>true</lineannotation>
|
|
'abc' LIKE '_b_' <lineannotation>true</lineannotation>
|
|
'abc' LIKE 'c' <lineannotation>false</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
<function>LIKE</function> pattern matching always covers the entire
|
|
string. Therefore, if it's desired to match a sequence anywhere within
|
|
a string, the pattern must start and end with a percent sign.
|
|
</para>
|
|
|
|
<para>
|
|
To match a literal underscore or percent sign without matching
|
|
other characters, the respective character in
|
|
<replaceable>pattern</replaceable> must be
|
|
preceded by the escape character. The default escape
|
|
character is the backslash but a different one can be selected by
|
|
using the <literal>ESCAPE</literal> clause. To match the escape
|
|
character itself, write two escape characters.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
If you have <xref linkend="guc-standard-conforming-strings"/> turned off,
|
|
any backslashes you write in literal string constants will need to be
|
|
doubled. See <xref linkend="sql-syntax-strings"/> for more information.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
It's also possible to select no escape character by writing
|
|
<literal>ESCAPE ''</literal>. This effectively disables the
|
|
escape mechanism, which makes it impossible to turn off the
|
|
special meaning of underscore and percent signs in the pattern.
|
|
</para>
|
|
|
|
<para>
|
|
According to the SQL standard, omitting <literal>ESCAPE</literal>
|
|
means there is no escape character (rather than defaulting to a
|
|
backslash), and a zero-length <literal>ESCAPE</literal> value is
|
|
disallowed. <productname>PostgreSQL</productname>'s behavior in
|
|
this regard is therefore slightly nonstandard.
|
|
</para>
|
|
|
|
<para>
|
|
The key word <token>ILIKE</token> can be used instead of
|
|
<token>LIKE</token> to make the match case-insensitive according
|
|
to the active locale. This is not in the <acronym>SQL</acronym> standard but is a
|
|
<productname>PostgreSQL</productname> extension.
|
|
</para>
|
|
|
|
<para>
|
|
The operator <literal>~~</literal> is equivalent to
|
|
<function>LIKE</function>, and <literal>~~*</literal> corresponds to
|
|
<function>ILIKE</function>. There are also
|
|
<literal>!~~</literal> and <literal>!~~*</literal> operators that
|
|
represent <function>NOT LIKE</function> and <function>NOT
|
|
ILIKE</function>, respectively. All of these operators are
|
|
<productname>PostgreSQL</productname>-specific. You may see these
|
|
operator names in <command>EXPLAIN</command> output and similar
|
|
places, since the parser actually translates <function>LIKE</function>
|
|
et al. to these operators.
|
|
</para>
|
|
|
|
<para>
|
|
The phrases <function>LIKE</function>, <function>ILIKE</function>,
|
|
<function>NOT LIKE</function>, and <function>NOT ILIKE</function> are
|
|
generally treated as operators
|
|
in <productname>PostgreSQL</productname> syntax; for example they can
|
|
be used in <replaceable>expression</replaceable>
|
|
<replaceable>operator</replaceable> ANY
|
|
(<replaceable>subquery</replaceable>) constructs, although
|
|
an <literal>ESCAPE</literal> clause cannot be included there. In some
|
|
obscure cases it may be necessary to use the underlying operator names
|
|
instead.
|
|
</para>
|
|
|
|
<para>
|
|
Also see the starts-with operator <literal>^@</literal> and the
|
|
corresponding <function>starts_with()</function> function, which are
|
|
useful in cases where simply matching the beginning of a string is
|
|
needed.
|
|
</para>
|
|
</sect2>
|
|
|
|
|
|
<sect2 id="functions-similarto-regexp">
|
|
<title><function>SIMILAR TO</function> Regular Expressions</title>
|
|
|
|
<indexterm>
|
|
<primary>regular expression</primary>
|
|
<!-- <seealso>pattern matching</seealso> breaks index build -->
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>SIMILAR TO</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>substring</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<replaceable>string</replaceable> SIMILAR TO <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
|
|
<replaceable>string</replaceable> NOT SIMILAR TO <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>SIMILAR TO</function> operator returns true or
|
|
false depending on whether its pattern matches the given string.
|
|
It is similar to <function>LIKE</function>, except that it
|
|
interprets the pattern using the SQL standard's definition of a
|
|
regular expression. SQL regular expressions are a curious cross
|
|
between <function>LIKE</function> notation and common (POSIX) regular
|
|
expression notation.
|
|
</para>
|
|
|
|
<para>
|
|
Like <function>LIKE</function>, the <function>SIMILAR TO</function>
|
|
operator succeeds only if its pattern matches the entire string;
|
|
this is unlike common regular expression behavior where the pattern
|
|
can match any part of the string.
|
|
Also like
|
|
<function>LIKE</function>, <function>SIMILAR TO</function> uses
|
|
<literal>_</literal> and <literal>%</literal> as wildcard characters denoting
|
|
any single character and any string, respectively (these are
|
|
comparable to <literal>.</literal> and <literal>.*</literal> in POSIX regular
|
|
expressions).
|
|
</para>
|
|
|
|
<para>
|
|
In addition to these facilities borrowed from <function>LIKE</function>,
|
|
<function>SIMILAR TO</function> supports these pattern-matching
|
|
metacharacters borrowed from POSIX regular expressions:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
<literal>|</literal> denotes alternation (either of two alternatives).
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>*</literal> denotes repetition of the previous item zero
|
|
or more times.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>+</literal> denotes repetition of the previous item one
|
|
or more times.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>?</literal> denotes repetition of the previous item zero
|
|
or one time.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>{</literal><replaceable>m</replaceable><literal>}</literal> denotes repetition
|
|
of the previous item exactly <replaceable>m</replaceable> times.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>{</literal><replaceable>m</replaceable><literal>,}</literal> denotes repetition
|
|
of the previous item <replaceable>m</replaceable> or more times.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>{</literal><replaceable>m</replaceable><literal>,</literal><replaceable>n</replaceable><literal>}</literal>
|
|
denotes repetition of the previous item at least <replaceable>m</replaceable> and
|
|
not more than <replaceable>n</replaceable> times.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Parentheses <literal>()</literal> can be used to group items into
|
|
a single logical item.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
A bracket expression <literal>[...]</literal> specifies a character
|
|
class, just as in POSIX regular expressions.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
Notice that the period (<literal>.</literal>) is not a metacharacter
|
|
for <function>SIMILAR TO</function>.
|
|
</para>
|
|
|
|
<para>
|
|
As with <function>LIKE</function>, a backslash disables the special
|
|
meaning of any of these metacharacters. A different escape character
|
|
can be specified with <literal>ESCAPE</literal>, or the escape
|
|
capability can be disabled by writing <literal>ESCAPE ''</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
According to the SQL standard, omitting <literal>ESCAPE</literal>
|
|
means there is no escape character (rather than defaulting to a
|
|
backslash), and a zero-length <literal>ESCAPE</literal> value is
|
|
disallowed. <productname>PostgreSQL</productname>'s behavior in
|
|
this regard is therefore slightly nonstandard.
|
|
</para>
|
|
|
|
<para>
|
|
Another nonstandard extension is that following the escape character
|
|
with a letter or digit provides access to the escape sequences
|
|
defined for POSIX regular expressions; see
|
|
<xref linkend="posix-character-entry-escapes-table"/>,
|
|
<xref linkend="posix-class-shorthand-escapes-table"/>, and
|
|
<xref linkend="posix-constraint-escapes-table"/> below.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
'abc' SIMILAR TO 'abc' <lineannotation>true</lineannotation>
|
|
'abc' SIMILAR TO 'a' <lineannotation>false</lineannotation>
|
|
'abc' SIMILAR TO '%(b|d)%' <lineannotation>true</lineannotation>
|
|
'abc' SIMILAR TO '(b|c)%' <lineannotation>false</lineannotation>
|
|
'-abc-' SIMILAR TO '%\mabc\M%' <lineannotation>true</lineannotation>
|
|
'xabcy' SIMILAR TO '%\mabc\M%' <lineannotation>false</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The <function>substring</function> function with three parameters
|
|
provides extraction of a substring that matches an SQL
|
|
regular expression pattern. The function can be written according
|
|
to standard SQL syntax:
|
|
<synopsis>
|
|
substring(<replaceable>string</replaceable> similar <replaceable>pattern</replaceable> escape <replaceable>escape-character</replaceable>)
|
|
</synopsis>
|
|
or using the now obsolete SQL:1999 syntax:
|
|
<synopsis>
|
|
substring(<replaceable>string</replaceable> from <replaceable>pattern</replaceable> for <replaceable>escape-character</replaceable>)
|
|
</synopsis>
|
|
or as a plain three-argument function:
|
|
<synopsis>
|
|
substring(<replaceable>string</replaceable>, <replaceable>pattern</replaceable>, <replaceable>escape-character</replaceable>)
|
|
</synopsis>
|
|
As with <literal>SIMILAR TO</literal>, the
|
|
specified pattern must match the entire data string, or else the
|
|
function fails and returns null. To indicate the part of the
|
|
pattern for which the matching data sub-string is of interest,
|
|
the pattern should contain
|
|
two occurrences of the escape character followed by a double quote
|
|
(<literal>"</literal>). <!-- " font-lock sanity -->
|
|
The text matching the portion of the pattern
|
|
between these separators is returned when the match is successful.
|
|
</para>
|
|
|
|
<para>
|
|
The escape-double-quote separators actually
|
|
divide <function>substring</function>'s pattern into three independent
|
|
regular expressions; for example, a vertical bar (<literal>|</literal>)
|
|
in any of the three sections affects only that section. Also, the first
|
|
and third of these regular expressions are defined to match the smallest
|
|
possible amount of text, not the largest, when there is any ambiguity
|
|
about how much of the data string matches which pattern. (In POSIX
|
|
parlance, the first and third regular expressions are forced to be
|
|
non-greedy.)
|
|
</para>
|
|
|
|
<para>
|
|
As an extension to the SQL standard, <productname>PostgreSQL</productname>
|
|
allows there to be just one escape-double-quote separator, in which case
|
|
the third regular expression is taken as empty; or no separators, in which
|
|
case the first and third regular expressions are taken as empty.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples, with <literal>#"</literal> delimiting the return string:
|
|
<programlisting>
|
|
substring('foobar' similar '%#"o_b#"%' escape '#') <lineannotation>oob</lineannotation>
|
|
substring('foobar' similar '#"o_b#"%' escape '#') <lineannotation>NULL</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-posix-regexp">
|
|
<title><acronym>POSIX</acronym> Regular Expressions</title>
|
|
|
|
<indexterm zone="functions-posix-regexp">
|
|
<primary>regular expression</primary>
|
|
<seealso>pattern matching</seealso>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>substring</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regexp_count</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regexp_instr</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regexp_like</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regexp_match</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regexp_matches</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regexp_replace</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regexp_split_to_table</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regexp_split_to_array</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regexp_substr</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<xref linkend="functions-posix-table"/> lists the available
|
|
operators for pattern matching using POSIX regular expressions.
|
|
</para>
|
|
|
|
<table id="functions-posix-table">
|
|
<title>Regular Expression Match Operators</title>
|
|
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>text</type> <literal>~</literal> <type>text</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
String matches regular expression, case sensitively
|
|
</para>
|
|
<para>
|
|
<literal>'thomas' ~ 't.*ma'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>text</type> <literal>~*</literal> <type>text</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
String matches regular expression, case-insensitively
|
|
</para>
|
|
<para>
|
|
<literal>'thomas' ~* 'T.*ma'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>text</type> <literal>!~</literal> <type>text</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
String does not match regular expression, case sensitively
|
|
</para>
|
|
<para>
|
|
<literal>'thomas' !~ 't.*max'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>text</type> <literal>!~*</literal> <type>text</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
String does not match regular expression, case-insensitively
|
|
</para>
|
|
<para>
|
|
<literal>'thomas' !~* 'T.*ma'</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<acronym>POSIX</acronym> regular expressions provide a more
|
|
powerful means for pattern matching than the <function>LIKE</function> and
|
|
<function>SIMILAR TO</function> operators.
|
|
Many Unix tools such as <command>egrep</command>,
|
|
<command>sed</command>, or <command>awk</command> use a pattern
|
|
matching language that is similar to the one described here.
|
|
</para>
|
|
|
|
<para>
|
|
A regular expression is a character sequence that is an
|
|
abbreviated definition of a set of strings (a <firstterm>regular
|
|
set</firstterm>). A string is said to match a regular expression
|
|
if it is a member of the regular set described by the regular
|
|
expression. As with <function>LIKE</function>, pattern characters
|
|
match string characters exactly unless they are special characters
|
|
in the regular expression language — but regular expressions use
|
|
different special characters than <function>LIKE</function> does.
|
|
Unlike <function>LIKE</function> patterns, a
|
|
regular expression is allowed to match anywhere within a string, unless
|
|
the regular expression is explicitly anchored to the beginning or
|
|
end of the string.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
'abcd' ~ 'bc' <lineannotation>true</lineannotation>
|
|
'abcd' ~ 'a.c' <lineannotation>true — dot matches any character</lineannotation>
|
|
'abcd' ~ 'a.*d' <lineannotation>true — <literal>*</literal> repeats the preceding pattern item</lineannotation>
|
|
'abcd' ~ '(b|x)' <lineannotation>true — <literal>|</literal> means OR, parentheses group</lineannotation>
|
|
'abcd' ~ '^a' <lineannotation>true — <literal>^</literal> anchors to start of string</lineannotation>
|
|
'abcd' ~ '^(b|c)' <lineannotation>false — would match except for anchoring</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The <acronym>POSIX</acronym> pattern language is described in much
|
|
greater detail below.
|
|
</para>
|
|
|
|
<para>
|
|
The <function>substring</function> function with two parameters,
|
|
<function>substring(<replaceable>string</replaceable> from
|
|
<replaceable>pattern</replaceable>)</function>, provides extraction of a
|
|
substring
|
|
that matches a POSIX regular expression pattern. It returns null if
|
|
there is no match, otherwise the first portion of the text that matched the
|
|
pattern. But if the pattern contains any parentheses, the portion
|
|
of the text that matched the first parenthesized subexpression (the
|
|
one whose left parenthesis comes first) is
|
|
returned. You can put parentheses around the whole expression
|
|
if you want to use parentheses within it without triggering this
|
|
exception. If you need parentheses in the pattern before the
|
|
subexpression you want to extract, see the non-capturing parentheses
|
|
described below.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
substring('foobar' from 'o.b') <lineannotation>oob</lineannotation>
|
|
substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The <function>regexp_count</function> function counts the number of
|
|
places where a POSIX regular expression pattern matches a string.
|
|
It has the syntax
|
|
<function>regexp_count</function>(<replaceable>string</replaceable>,
|
|
<replaceable>pattern</replaceable>
|
|
<optional>, <replaceable>start</replaceable>
|
|
<optional>, <replaceable>flags</replaceable>
|
|
</optional></optional>).
|
|
<replaceable>pattern</replaceable> is searched for
|
|
in <replaceable>string</replaceable>, normally from the beginning of
|
|
the string, but if the <replaceable>start</replaceable> parameter is
|
|
provided then beginning from that character index.
|
|
The <replaceable>flags</replaceable> parameter is an optional text
|
|
string containing zero or more single-letter flags that change the
|
|
function's behavior. For example, including <literal>i</literal> in
|
|
<replaceable>flags</replaceable> specifies case-insensitive matching.
|
|
Supported flags are described in
|
|
<xref linkend="posix-embedded-options-table"/>.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
regexp_count('ABCABCAXYaxy', 'A.') <lineannotation>3</lineannotation>
|
|
regexp_count('ABCABCAXYaxy', 'A.', 1, 'i') <lineannotation>4</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The <function>regexp_instr</function> function returns the starting or
|
|
ending position of the <replaceable>N</replaceable>'th match of a
|
|
POSIX regular expression pattern to a string, or zero if there is no
|
|
such match. It has the syntax
|
|
<function>regexp_instr</function>(<replaceable>string</replaceable>,
|
|
<replaceable>pattern</replaceable>
|
|
<optional>, <replaceable>start</replaceable>
|
|
<optional>, <replaceable>N</replaceable>
|
|
<optional>, <replaceable>endoption</replaceable>
|
|
<optional>, <replaceable>flags</replaceable>
|
|
<optional>, <replaceable>subexpr</replaceable>
|
|
</optional></optional></optional></optional></optional>).
|
|
<replaceable>pattern</replaceable> is searched for
|
|
in <replaceable>string</replaceable>, normally from the beginning of
|
|
the string, but if the <replaceable>start</replaceable> parameter is
|
|
provided then beginning from that character index.
|
|
If <replaceable>N</replaceable> is specified
|
|
then the <replaceable>N</replaceable>'th match of the pattern
|
|
is located, otherwise the first match is located.
|
|
If the <replaceable>endoption</replaceable> parameter is omitted or
|
|
specified as zero, the function returns the position of the first
|
|
character of the match. Otherwise, <replaceable>endoption</replaceable>
|
|
must be one, and the function returns the position of the character
|
|
following the match.
|
|
The <replaceable>flags</replaceable> parameter is an optional text
|
|
string containing zero or more single-letter flags that change the
|
|
function's behavior. Supported flags are described
|
|
in <xref linkend="posix-embedded-options-table"/>.
|
|
For a pattern containing parenthesized
|
|
subexpressions, <replaceable>subexpr</replaceable> is an integer
|
|
indicating which subexpression is of interest: the result identifies
|
|
the position of the substring matching that subexpression.
|
|
Subexpressions are numbered in the order of their leading parentheses.
|
|
When <replaceable>subexpr</replaceable> is omitted or zero, the result
|
|
identifies the position of the whole match regardless of
|
|
parenthesized subexpressions.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
regexp_instr('number of your street, town zip, FR', '[^,]+', 1, 2)
|
|
<lineannotation>23</lineannotation>
|
|
regexp_instr('ABCDEFGHI', '(c..)(...)', 1, 1, 0, 'i', 2)
|
|
<lineannotation>6</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The <function>regexp_like</function> function checks whether a match
|
|
of a POSIX regular expression pattern occurs within a string,
|
|
returning boolean true or false. It has the syntax
|
|
<function>regexp_like</function>(<replaceable>string</replaceable>,
|
|
<replaceable>pattern</replaceable>
|
|
<optional>, <replaceable>flags</replaceable> </optional>).
|
|
The <replaceable>flags</replaceable> parameter is an optional text
|
|
string containing zero or more single-letter flags that change the
|
|
function's behavior. Supported flags are described
|
|
in <xref linkend="posix-embedded-options-table"/>.
|
|
This function has the same results as the <literal>~</literal>
|
|
operator if no flags are specified. If only the <literal>i</literal>
|
|
flag is specified, it has the same results as
|
|
the <literal>~*</literal> operator.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
regexp_like('Hello World', 'world') <lineannotation>false</lineannotation>
|
|
regexp_like('Hello World', 'world', 'i') <lineannotation>true</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The <function>regexp_match</function> function returns a text array of
|
|
matching substring(s) within the first match of a POSIX
|
|
regular expression pattern to a string. It has the syntax
|
|
<function>regexp_match</function>(<replaceable>string</replaceable>,
|
|
<replaceable>pattern</replaceable> <optional>, <replaceable>flags</replaceable> </optional>).
|
|
If there is no match, the result is <literal>NULL</literal>.
|
|
If a match is found, and the <replaceable>pattern</replaceable> contains no
|
|
parenthesized subexpressions, then the result is a single-element text
|
|
array containing the substring matching the whole pattern.
|
|
If a match is found, and the <replaceable>pattern</replaceable> contains
|
|
parenthesized subexpressions, then the result is a text array
|
|
whose <replaceable>n</replaceable>'th element is the substring matching
|
|
the <replaceable>n</replaceable>'th parenthesized subexpression of
|
|
the <replaceable>pattern</replaceable> (not counting <quote>non-capturing</quote>
|
|
parentheses; see below for details).
|
|
The <replaceable>flags</replaceable> parameter is an optional text string
|
|
containing zero or more single-letter flags that change the function's
|
|
behavior. Supported flags are described
|
|
in <xref linkend="posix-embedded-options-table"/>.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
SELECT regexp_match('foobarbequebaz', 'bar.*que');
|
|
regexp_match
|
|
--------------
|
|
{barbeque}
|
|
(1 row)
|
|
|
|
SELECT regexp_match('foobarbequebaz', '(bar)(beque)');
|
|
regexp_match
|
|
--------------
|
|
{bar,beque}
|
|
(1 row)
|
|
</programlisting>
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
In the common case where you just want the whole matching substring
|
|
or <literal>NULL</literal> for no match, the best solution is to
|
|
use <function>regexp_substr()</function>.
|
|
However, <function>regexp_substr()</function> only exists
|
|
in <productname>PostgreSQL</productname> version 15 and up. When
|
|
working in older versions, you can extract the first element
|
|
of <function>regexp_match()</function>'s result, for example:
|
|
<programlisting>
|
|
SELECT (regexp_match('foobarbequebaz', 'bar.*que'))[1];
|
|
regexp_match
|
|
--------------
|
|
barbeque
|
|
(1 row)
|
|
</programlisting>
|
|
</para>
|
|
</tip>
|
|
|
|
<para>
|
|
The <function>regexp_matches</function> function returns a set of text arrays
|
|
of matching substring(s) within matches of a POSIX regular
|
|
expression pattern to a string. It has the same syntax as
|
|
<function>regexp_match</function>.
|
|
This function returns no rows if there is no match, one row if there is
|
|
a match and the <literal>g</literal> flag is not given, or <replaceable>N</replaceable>
|
|
rows if there are <replaceable>N</replaceable> matches and the <literal>g</literal> flag
|
|
is given. Each returned row is a text array containing the whole
|
|
matched substring or the substrings matching parenthesized
|
|
subexpressions of the <replaceable>pattern</replaceable>, just as described above
|
|
for <function>regexp_match</function>.
|
|
<function>regexp_matches</function> accepts all the flags shown
|
|
in <xref linkend="posix-embedded-options-table"/>, plus
|
|
the <literal>g</literal> flag which commands it to return all matches, not
|
|
just the first one.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
SELECT regexp_matches('foo', 'not there');
|
|
regexp_matches
|
|
----------------
|
|
(0 rows)
|
|
|
|
SELECT regexp_matches('foobarbequebazilbarfbonk', '(b[^b]+)(b[^b]+)', 'g');
|
|
regexp_matches
|
|
----------------
|
|
{bar,beque}
|
|
{bazil,barf}
|
|
(2 rows)
|
|
</programlisting>
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
In most cases <function>regexp_matches()</function> should be used with
|
|
the <literal>g</literal> flag, since if you only want the first match, it's
|
|
easier and more efficient to use <function>regexp_match()</function>.
|
|
However, <function>regexp_match()</function> only exists
|
|
in <productname>PostgreSQL</productname> version 10 and up. When working in older
|
|
versions, a common trick is to place a <function>regexp_matches()</function>
|
|
call in a sub-select, for example:
|
|
<programlisting>
|
|
SELECT col1, (SELECT regexp_matches(col2, '(bar)(beque)')) FROM tab;
|
|
</programlisting>
|
|
This produces a text array if there's a match, or <literal>NULL</literal> if
|
|
not, the same as <function>regexp_match()</function> would do. Without the
|
|
sub-select, this query would produce no output at all for table rows
|
|
without a match, which is typically not the desired behavior.
|
|
</para>
|
|
</tip>
|
|
|
|
<para>
|
|
The <function>regexp_replace</function> function provides substitution of
|
|
new text for substrings that match POSIX regular expression patterns.
|
|
It has the syntax
|
|
<function>regexp_replace</function>(<replaceable>source</replaceable>,
|
|
<replaceable>pattern</replaceable>, <replaceable>replacement</replaceable>
|
|
<optional>, <replaceable>start</replaceable>
|
|
<optional>, <replaceable>N</replaceable>
|
|
</optional></optional>
|
|
<optional>, <replaceable>flags</replaceable> </optional>).
|
|
(Notice that <replaceable>N</replaceable> cannot be specified
|
|
unless <replaceable>start</replaceable> is,
|
|
but <replaceable>flags</replaceable> can be given in any case.)
|
|
The <replaceable>source</replaceable> string is returned unchanged if
|
|
there is no match to the <replaceable>pattern</replaceable>. If there is a
|
|
match, the <replaceable>source</replaceable> string is returned with the
|
|
<replaceable>replacement</replaceable> string substituted for the matching
|
|
substring. The <replaceable>replacement</replaceable> string can contain
|
|
<literal>\</literal><replaceable>n</replaceable>, where <replaceable>n</replaceable> is 1
|
|
through 9, to indicate that the source substring matching the
|
|
<replaceable>n</replaceable>'th parenthesized subexpression of the pattern should be
|
|
inserted, and it can contain <literal>\&</literal> to indicate that the
|
|
substring matching the entire pattern should be inserted. Write
|
|
<literal>\\</literal> if you need to put a literal backslash in the replacement
|
|
text.
|
|
<replaceable>pattern</replaceable> is searched for
|
|
in <replaceable>string</replaceable>, normally from the beginning of
|
|
the string, but if the <replaceable>start</replaceable> parameter is
|
|
provided then beginning from that character index.
|
|
By default, only the first match of the pattern is replaced.
|
|
If <replaceable>N</replaceable> is specified and is greater than zero,
|
|
then the <replaceable>N</replaceable>'th match of the pattern
|
|
is replaced.
|
|
If the <literal>g</literal> flag is given, or
|
|
if <replaceable>N</replaceable> is specified and is zero, then all
|
|
matches at or after the <replaceable>start</replaceable> position are
|
|
replaced. (The <literal>g</literal> flag is ignored
|
|
when <replaceable>N</replaceable> is specified.)
|
|
The <replaceable>flags</replaceable> parameter is an optional text
|
|
string containing zero or more single-letter flags that change the
|
|
function's behavior. Supported flags (though
|
|
not <literal>g</literal>) are
|
|
described in <xref linkend="posix-embedded-options-table"/>.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
regexp_replace('foobarbaz', 'b..', 'X')
|
|
<lineannotation>fooXbaz</lineannotation>
|
|
regexp_replace('foobarbaz', 'b..', 'X', 'g')
|
|
<lineannotation>fooXX</lineannotation>
|
|
regexp_replace('foobarbaz', 'b(..)', 'X\1Y', 'g')
|
|
<lineannotation>fooXarYXazY</lineannotation>
|
|
regexp_replace('A PostgreSQL function', 'a|e|i|o|u', 'X', 1, 0, 'i')
|
|
<lineannotation>X PXstgrXSQL fXnctXXn</lineannotation>
|
|
regexp_replace('A PostgreSQL function', 'a|e|i|o|u', 'X', 1, 3, 'i')
|
|
<lineannotation>A PostgrXSQL function</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The <function>regexp_split_to_table</function> function splits a string using a POSIX
|
|
regular expression pattern as a delimiter. It has the syntax
|
|
<function>regexp_split_to_table</function>(<replaceable>string</replaceable>, <replaceable>pattern</replaceable>
|
|
<optional>, <replaceable>flags</replaceable> </optional>).
|
|
If there is no match to the <replaceable>pattern</replaceable>, the function returns the
|
|
<replaceable>string</replaceable>. If there is at least one match, for each match it returns
|
|
the text from the end of the last match (or the beginning of the string)
|
|
to the beginning of the match. When there are no more matches, it
|
|
returns the text from the end of the last match to the end of the string.
|
|
The <replaceable>flags</replaceable> parameter is an optional text string containing
|
|
zero or more single-letter flags that change the function's behavior.
|
|
<function>regexp_split_to_table</function> supports the flags described in
|
|
<xref linkend="posix-embedded-options-table"/>.
|
|
</para>
|
|
|
|
<para>
|
|
The <function>regexp_split_to_array</function> function behaves the same as
|
|
<function>regexp_split_to_table</function>, except that <function>regexp_split_to_array</function>
|
|
returns its result as an array of <type>text</type>. It has the syntax
|
|
<function>regexp_split_to_array</function>(<replaceable>string</replaceable>, <replaceable>pattern</replaceable>
|
|
<optional>, <replaceable>flags</replaceable> </optional>).
|
|
The parameters are the same as for <function>regexp_split_to_table</function>.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
SELECT foo FROM regexp_split_to_table('the quick brown fox jumps over the lazy dog', '\s+') AS foo;
|
|
foo
|
|
-------
|
|
the
|
|
quick
|
|
brown
|
|
fox
|
|
jumps
|
|
over
|
|
the
|
|
lazy
|
|
dog
|
|
(9 rows)
|
|
|
|
SELECT regexp_split_to_array('the quick brown fox jumps over the lazy dog', '\s+');
|
|
regexp_split_to_array
|
|
-----------------------------------------------
|
|
{the,quick,brown,fox,jumps,over,the,lazy,dog}
|
|
(1 row)
|
|
|
|
SELECT foo FROM regexp_split_to_table('the quick brown fox', '\s*') AS foo;
|
|
foo
|
|
-----
|
|
t
|
|
h
|
|
e
|
|
q
|
|
u
|
|
i
|
|
c
|
|
k
|
|
b
|
|
r
|
|
o
|
|
w
|
|
n
|
|
f
|
|
o
|
|
x
|
|
(16 rows)
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
As the last example demonstrates, the regexp split functions ignore
|
|
zero-length matches that occur at the start or end of the string
|
|
or immediately after a previous match. This is contrary to the strict
|
|
definition of regexp matching that is implemented by
|
|
the other regexp functions, but is usually the most convenient behavior
|
|
in practice. Other software systems such as Perl use similar definitions.
|
|
</para>
|
|
|
|
<para>
|
|
The <function>regexp_substr</function> function returns the substring
|
|
that matches a POSIX regular expression pattern,
|
|
or <literal>NULL</literal> if there is no match. It has the syntax
|
|
<function>regexp_substr</function>(<replaceable>string</replaceable>,
|
|
<replaceable>pattern</replaceable>
|
|
<optional>, <replaceable>start</replaceable>
|
|
<optional>, <replaceable>N</replaceable>
|
|
<optional>, <replaceable>flags</replaceable>
|
|
<optional>, <replaceable>subexpr</replaceable>
|
|
</optional></optional></optional></optional>).
|
|
<replaceable>pattern</replaceable> is searched for
|
|
in <replaceable>string</replaceable>, normally from the beginning of
|
|
the string, but if the <replaceable>start</replaceable> parameter is
|
|
provided then beginning from that character index.
|
|
If <replaceable>N</replaceable> is specified
|
|
then the <replaceable>N</replaceable>'th match of the pattern
|
|
is returned, otherwise the first match is returned.
|
|
The <replaceable>flags</replaceable> parameter is an optional text
|
|
string containing zero or more single-letter flags that change the
|
|
function's behavior. Supported flags are described
|
|
in <xref linkend="posix-embedded-options-table"/>.
|
|
For a pattern containing parenthesized
|
|
subexpressions, <replaceable>subexpr</replaceable> is an integer
|
|
indicating which subexpression is of interest: the result is the
|
|
substring matching that subexpression.
|
|
Subexpressions are numbered in the order of their leading parentheses.
|
|
When <replaceable>subexpr</replaceable> is omitted or zero, the result
|
|
is the whole match regardless of parenthesized subexpressions.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<programlisting>
|
|
regexp_substr('number of your street, town zip, FR', '[^,]+', 1, 2)
|
|
<lineannotation> town zip</lineannotation>
|
|
regexp_substr('ABCDEFGHI', '(c..)(...)', 1, 1, 'i', 2)
|
|
<lineannotation>FGH</lineannotation>
|
|
</programlisting>
|
|
</para>
|
|
|
|
<!-- derived from the re_syntax.n man page -->
|
|
|
|
<sect3 id="posix-syntax-details">
|
|
<title>Regular Expression Details</title>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname>'s regular expressions are implemented
|
|
using a software package written by Henry Spencer. Much of
|
|
the description of regular expressions below is copied verbatim from his
|
|
manual.
|
|
</para>
|
|
|
|
<para>
|
|
Regular expressions (<acronym>RE</acronym>s), as defined in
|
|
<acronym>POSIX</acronym> 1003.2, come in two forms:
|
|
<firstterm>extended</firstterm> <acronym>RE</acronym>s or <acronym>ERE</acronym>s
|
|
(roughly those of <command>egrep</command>), and
|
|
<firstterm>basic</firstterm> <acronym>RE</acronym>s or <acronym>BRE</acronym>s
|
|
(roughly those of <command>ed</command>).
|
|
<productname>PostgreSQL</productname> supports both forms, and
|
|
also implements some extensions
|
|
that are not in the POSIX standard, but have become widely used
|
|
due to their availability in programming languages such as Perl and Tcl.
|
|
<acronym>RE</acronym>s using these non-POSIX extensions are called
|
|
<firstterm>advanced</firstterm> <acronym>RE</acronym>s or <acronym>ARE</acronym>s
|
|
in this documentation. AREs are almost an exact superset of EREs,
|
|
but BREs have several notational incompatibilities (as well as being
|
|
much more limited).
|
|
We first describe the ARE and ERE forms, noting features that apply
|
|
only to AREs, and then describe how BREs differ.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
<productname>PostgreSQL</productname> always initially presumes that a regular
|
|
expression follows the ARE rules. However, the more limited ERE or
|
|
BRE rules can be chosen by prepending an <firstterm>embedded option</firstterm>
|
|
to the RE pattern, as described in <xref linkend="posix-metasyntax"/>.
|
|
This can be useful for compatibility with applications that expect
|
|
exactly the <acronym>POSIX</acronym> 1003.2 rules.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
A regular expression is defined as one or more
|
|
<firstterm>branches</firstterm>, separated by
|
|
<literal>|</literal>. It matches anything that matches one of the
|
|
branches.
|
|
</para>
|
|
|
|
<para>
|
|
A branch is zero or more <firstterm>quantified atoms</firstterm> or
|
|
<firstterm>constraints</firstterm>, concatenated.
|
|
It matches a match for the first, followed by a match for the second, etc.;
|
|
an empty branch matches the empty string.
|
|
</para>
|
|
|
|
<para>
|
|
A quantified atom is an <firstterm>atom</firstterm> possibly followed
|
|
by a single <firstterm>quantifier</firstterm>.
|
|
Without a quantifier, it matches a match for the atom.
|
|
With a quantifier, it can match some number of matches of the atom.
|
|
An <firstterm>atom</firstterm> can be any of the possibilities
|
|
shown in <xref linkend="posix-atoms-table"/>.
|
|
The possible quantifiers and their meanings are shown in
|
|
<xref linkend="posix-quantifiers-table"/>.
|
|
</para>
|
|
|
|
<para>
|
|
A <firstterm>constraint</firstterm> matches an empty string, but matches only when
|
|
specific conditions are met. A constraint can be used where an atom
|
|
could be used, except it cannot be followed by a quantifier.
|
|
The simple constraints are shown in
|
|
<xref linkend="posix-constraints-table"/>;
|
|
some more constraints are described later.
|
|
</para>
|
|
|
|
|
|
<table id="posix-atoms-table">
|
|
<title>Regular Expression Atoms</title>
|
|
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Atom</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry> <literal>(</literal><replaceable>re</replaceable><literal>)</literal> </entry>
|
|
<entry> (where <replaceable>re</replaceable> is any regular expression)
|
|
matches a match for
|
|
<replaceable>re</replaceable>, with the match noted for possible reporting </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>(?:</literal><replaceable>re</replaceable><literal>)</literal> </entry>
|
|
<entry> as above, but the match is not noted for reporting
|
|
(a <quote>non-capturing</quote> set of parentheses)
|
|
(AREs only) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>.</literal> </entry>
|
|
<entry> matches any single character </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>[</literal><replaceable>chars</replaceable><literal>]</literal> </entry>
|
|
<entry> a <firstterm>bracket expression</firstterm>,
|
|
matching any one of the <replaceable>chars</replaceable> (see
|
|
<xref linkend="posix-bracket-expressions"/> for more detail) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\</literal><replaceable>k</replaceable> </entry>
|
|
<entry> (where <replaceable>k</replaceable> is a non-alphanumeric character)
|
|
matches that character taken as an ordinary character,
|
|
e.g., <literal>\\</literal> matches a backslash character </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\</literal><replaceable>c</replaceable> </entry>
|
|
<entry> where <replaceable>c</replaceable> is alphanumeric
|
|
(possibly followed by other characters)
|
|
is an <firstterm>escape</firstterm>, see <xref linkend="posix-escape-sequences"/>
|
|
(AREs only; in EREs and BREs, this matches <replaceable>c</replaceable>) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>{</literal> </entry>
|
|
<entry> when followed by a character other than a digit,
|
|
matches the left-brace character <literal>{</literal>;
|
|
when followed by a digit, it is the beginning of a
|
|
<replaceable>bound</replaceable> (see below) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <replaceable>x</replaceable> </entry>
|
|
<entry> where <replaceable>x</replaceable> is a single character with no other
|
|
significance, matches that character </entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
An RE cannot end with a backslash (<literal>\</literal>).
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
If you have <xref linkend="guc-standard-conforming-strings"/> turned off,
|
|
any backslashes you write in literal string constants will need to be
|
|
doubled. See <xref linkend="sql-syntax-strings"/> for more information.
|
|
</para>
|
|
</note>
|
|
|
|
<table id="posix-quantifiers-table">
|
|
<title>Regular Expression Quantifiers</title>
|
|
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Quantifier</entry>
|
|
<entry>Matches</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry> <literal>*</literal> </entry>
|
|
<entry> a sequence of 0 or more matches of the atom </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>+</literal> </entry>
|
|
<entry> a sequence of 1 or more matches of the atom </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>?</literal> </entry>
|
|
<entry> a sequence of 0 or 1 matches of the atom </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>{</literal><replaceable>m</replaceable><literal>}</literal> </entry>
|
|
<entry> a sequence of exactly <replaceable>m</replaceable> matches of the atom </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>{</literal><replaceable>m</replaceable><literal>,}</literal> </entry>
|
|
<entry> a sequence of <replaceable>m</replaceable> or more matches of the atom </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>
|
|
<literal>{</literal><replaceable>m</replaceable><literal>,</literal><replaceable>n</replaceable><literal>}</literal> </entry>
|
|
<entry> a sequence of <replaceable>m</replaceable> through <replaceable>n</replaceable>
|
|
(inclusive) matches of the atom; <replaceable>m</replaceable> cannot exceed
|
|
<replaceable>n</replaceable> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>*?</literal> </entry>
|
|
<entry> non-greedy version of <literal>*</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>+?</literal> </entry>
|
|
<entry> non-greedy version of <literal>+</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>??</literal> </entry>
|
|
<entry> non-greedy version of <literal>?</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>{</literal><replaceable>m</replaceable><literal>}?</literal> </entry>
|
|
<entry> non-greedy version of <literal>{</literal><replaceable>m</replaceable><literal>}</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>{</literal><replaceable>m</replaceable><literal>,}?</literal> </entry>
|
|
<entry> non-greedy version of <literal>{</literal><replaceable>m</replaceable><literal>,}</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>
|
|
<literal>{</literal><replaceable>m</replaceable><literal>,</literal><replaceable>n</replaceable><literal>}?</literal> </entry>
|
|
<entry> non-greedy version of <literal>{</literal><replaceable>m</replaceable><literal>,</literal><replaceable>n</replaceable><literal>}</literal> </entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The forms using <literal>{</literal><replaceable>...</replaceable><literal>}</literal>
|
|
are known as <firstterm>bounds</firstterm>.
|
|
The numbers <replaceable>m</replaceable> and <replaceable>n</replaceable> within a bound are
|
|
unsigned decimal integers with permissible values from 0 to 255 inclusive.
|
|
</para>
|
|
|
|
<para>
|
|
<firstterm>Non-greedy</firstterm> quantifiers (available in AREs only) match the
|
|
same possibilities as their corresponding normal (<firstterm>greedy</firstterm>)
|
|
counterparts, but prefer the smallest number rather than the largest
|
|
number of matches.
|
|
See <xref linkend="posix-matching-rules"/> for more detail.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
A quantifier cannot immediately follow another quantifier, e.g.,
|
|
<literal>**</literal> is invalid.
|
|
A quantifier cannot
|
|
begin an expression or subexpression or follow
|
|
<literal>^</literal> or <literal>|</literal>.
|
|
</para>
|
|
</note>
|
|
|
|
<table id="posix-constraints-table">
|
|
<title>Regular Expression Constraints</title>
|
|
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Constraint</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry> <literal>^</literal> </entry>
|
|
<entry> matches at the beginning of the string </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>$</literal> </entry>
|
|
<entry> matches at the end of the string </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>(?=</literal><replaceable>re</replaceable><literal>)</literal> </entry>
|
|
<entry> <firstterm>positive lookahead</firstterm> matches at any point
|
|
where a substring matching <replaceable>re</replaceable> begins
|
|
(AREs only) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>(?!</literal><replaceable>re</replaceable><literal>)</literal> </entry>
|
|
<entry> <firstterm>negative lookahead</firstterm> matches at any point
|
|
where no substring matching <replaceable>re</replaceable> begins
|
|
(AREs only) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>(?<=</literal><replaceable>re</replaceable><literal>)</literal> </entry>
|
|
<entry> <firstterm>positive lookbehind</firstterm> matches at any point
|
|
where a substring matching <replaceable>re</replaceable> ends
|
|
(AREs only) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>(?<!</literal><replaceable>re</replaceable><literal>)</literal> </entry>
|
|
<entry> <firstterm>negative lookbehind</firstterm> matches at any point
|
|
where no substring matching <replaceable>re</replaceable> ends
|
|
(AREs only) </entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Lookahead and lookbehind constraints cannot contain <firstterm>back
|
|
references</firstterm> (see <xref linkend="posix-escape-sequences"/>),
|
|
and all parentheses within them are considered non-capturing.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="posix-bracket-expressions">
|
|
<title>Bracket Expressions</title>
|
|
|
|
<para>
|
|
A <firstterm>bracket expression</firstterm> is a list of
|
|
characters enclosed in <literal>[]</literal>. It normally matches
|
|
any single character from the list (but see below). If the list
|
|
begins with <literal>^</literal>, it matches any single character
|
|
<emphasis>not</emphasis> from the rest of the list.
|
|
If two characters
|
|
in the list are separated by <literal>-</literal>, this is
|
|
shorthand for the full range of characters between those two
|
|
(inclusive) in the collating sequence,
|
|
e.g., <literal>[0-9]</literal> in <acronym>ASCII</acronym> matches
|
|
any decimal digit. It is illegal for two ranges to share an
|
|
endpoint, e.g., <literal>a-c-e</literal>. Ranges are very
|
|
collating-sequence-dependent, so portable programs should avoid
|
|
relying on them.
|
|
</para>
|
|
|
|
<para>
|
|
To include a literal <literal>]</literal> in the list, make it the
|
|
first character (after <literal>^</literal>, if that is used). To
|
|
include a literal <literal>-</literal>, make it the first or last
|
|
character, or the second endpoint of a range. To use a literal
|
|
<literal>-</literal> as the first endpoint of a range, enclose it
|
|
in <literal>[.</literal> and <literal>.]</literal> to make it a
|
|
collating element (see below). With the exception of these characters,
|
|
some combinations using <literal>[</literal>
|
|
(see next paragraphs), and escapes (AREs only), all other special
|
|
characters lose their special significance within a bracket expression.
|
|
In particular, <literal>\</literal> is not special when following
|
|
ERE or BRE rules, though it is special (as introducing an escape)
|
|
in AREs.
|
|
</para>
|
|
|
|
<para>
|
|
Within a bracket expression, a collating element (a character, a
|
|
multiple-character sequence that collates as if it were a single
|
|
character, or a collating-sequence name for either) enclosed in
|
|
<literal>[.</literal> and <literal>.]</literal> stands for the
|
|
sequence of characters of that collating element. The sequence is
|
|
treated as a single element of the bracket expression's list. This
|
|
allows a bracket
|
|
expression containing a multiple-character collating element to
|
|
match more than one character, e.g., if the collating sequence
|
|
includes a <literal>ch</literal> collating element, then the RE
|
|
<literal>[[.ch.]]*c</literal> matches the first five characters of
|
|
<literal>chchcc</literal>.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
<productname>PostgreSQL</productname> currently does not support multi-character collating
|
|
elements. This information describes possible future behavior.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
Within a bracket expression, a collating element enclosed in
|
|
<literal>[=</literal> and <literal>=]</literal> is an <firstterm>equivalence
|
|
class</firstterm>, standing for the sequences of characters of all collating
|
|
elements equivalent to that one, including itself. (If there are
|
|
no other equivalent collating elements, the treatment is as if the
|
|
enclosing delimiters were <literal>[.</literal> and
|
|
<literal>.]</literal>.) For example, if <literal>o</literal> and
|
|
<literal>^</literal> are the members of an equivalence class, then
|
|
<literal>[[=o=]]</literal>, <literal>[[=^=]]</literal>, and
|
|
<literal>[o^]</literal> are all synonymous. An equivalence class
|
|
cannot be an endpoint of a range.
|
|
</para>
|
|
|
|
<para>
|
|
Within a bracket expression, the name of a character class
|
|
enclosed in <literal>[:</literal> and <literal>:]</literal> stands
|
|
for the list of all characters belonging to that class. A character
|
|
class cannot be used as an endpoint of a range.
|
|
The <acronym>POSIX</acronym> standard defines these character class
|
|
names:
|
|
<literal>alnum</literal> (letters and numeric digits),
|
|
<literal>alpha</literal> (letters),
|
|
<literal>blank</literal> (space and tab),
|
|
<literal>cntrl</literal> (control characters),
|
|
<literal>digit</literal> (numeric digits),
|
|
<literal>graph</literal> (printable characters except space),
|
|
<literal>lower</literal> (lower-case letters),
|
|
<literal>print</literal> (printable characters including space),
|
|
<literal>punct</literal> (punctuation),
|
|
<literal>space</literal> (any white space),
|
|
<literal>upper</literal> (upper-case letters),
|
|
and <literal>xdigit</literal> (hexadecimal digits).
|
|
The behavior of these standard character classes is generally
|
|
consistent across platforms for characters in the 7-bit ASCII set.
|
|
Whether a given non-ASCII character is considered to belong to one
|
|
of these classes depends on the <firstterm>collation</firstterm>
|
|
that is used for the regular-expression function or operator
|
|
(see <xref linkend="collation"/>), or by default on the
|
|
database's <envar>LC_CTYPE</envar> locale setting (see
|
|
<xref linkend="locale"/>). The classification of non-ASCII
|
|
characters can vary across platforms even in similarly-named
|
|
locales. (But the <literal>C</literal> locale never considers any
|
|
non-ASCII characters to belong to any of these classes.)
|
|
In addition to these standard character
|
|
classes, <productname>PostgreSQL</productname> defines
|
|
the <literal>word</literal> character class, which is the same as
|
|
<literal>alnum</literal> plus the underscore (<literal>_</literal>)
|
|
character, and
|
|
the <literal>ascii</literal> character class, which contains exactly
|
|
the 7-bit ASCII set.
|
|
</para>
|
|
|
|
<para>
|
|
There are two special cases of bracket expressions: the bracket
|
|
expressions <literal>[[:<:]]</literal> and
|
|
<literal>[[:>:]]</literal> are constraints,
|
|
matching empty strings at the beginning
|
|
and end of a word respectively. A word is defined as a sequence
|
|
of word characters that is neither preceded nor followed by word
|
|
characters. A word character is any character belonging to the
|
|
<literal>word</literal> character class, that is, any letter, digit,
|
|
or underscore. This is an extension, compatible with but not
|
|
specified by <acronym>POSIX</acronym> 1003.2, and should be used with
|
|
caution in software intended to be portable to other systems.
|
|
The constraint escapes described below are usually preferable; they
|
|
are no more standard, but are easier to type.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="posix-escape-sequences">
|
|
<title>Regular Expression Escapes</title>
|
|
|
|
<para>
|
|
<firstterm>Escapes</firstterm> are special sequences beginning with <literal>\</literal>
|
|
followed by an alphanumeric character. Escapes come in several varieties:
|
|
character entry, class shorthands, constraint escapes, and back references.
|
|
A <literal>\</literal> followed by an alphanumeric character but not constituting
|
|
a valid escape is illegal in AREs.
|
|
In EREs, there are no escapes: outside a bracket expression,
|
|
a <literal>\</literal> followed by an alphanumeric character merely stands for
|
|
that character as an ordinary character, and inside a bracket expression,
|
|
<literal>\</literal> is an ordinary character.
|
|
(The latter is the one actual incompatibility between EREs and AREs.)
|
|
</para>
|
|
|
|
<para>
|
|
<firstterm>Character-entry escapes</firstterm> exist to make it easier to specify
|
|
non-printing and other inconvenient characters in REs. They are
|
|
shown in <xref linkend="posix-character-entry-escapes-table"/>.
|
|
</para>
|
|
|
|
<para>
|
|
<firstterm>Class-shorthand escapes</firstterm> provide shorthands for certain
|
|
commonly-used character classes. They are
|
|
shown in <xref linkend="posix-class-shorthand-escapes-table"/>.
|
|
</para>
|
|
|
|
<para>
|
|
A <firstterm>constraint escape</firstterm> is a constraint,
|
|
matching the empty string if specific conditions are met,
|
|
written as an escape. They are
|
|
shown in <xref linkend="posix-constraint-escapes-table"/>.
|
|
</para>
|
|
|
|
<para>
|
|
A <firstterm>back reference</firstterm> (<literal>\</literal><replaceable>n</replaceable>) matches the
|
|
same string matched by the previous parenthesized subexpression specified
|
|
by the number <replaceable>n</replaceable>
|
|
(see <xref linkend="posix-constraint-backref-table"/>). For example,
|
|
<literal>([bc])\1</literal> matches <literal>bb</literal> or <literal>cc</literal>
|
|
but not <literal>bc</literal> or <literal>cb</literal>.
|
|
The subexpression must entirely precede the back reference in the RE.
|
|
Subexpressions are numbered in the order of their leading parentheses.
|
|
Non-capturing parentheses do not define subexpressions.
|
|
The back reference considers only the string characters matched by the
|
|
referenced subexpression, not any constraints contained in it. For
|
|
example, <literal>(^\d)\1</literal> will match <literal>22</literal>.
|
|
</para>
|
|
|
|
<table id="posix-character-entry-escapes-table">
|
|
<title>Regular Expression Character-Entry Escapes</title>
|
|
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Escape</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry> <literal>\a</literal> </entry>
|
|
<entry> alert (bell) character, as in C </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\b</literal> </entry>
|
|
<entry> backspace, as in C </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\B</literal> </entry>
|
|
<entry> synonym for backslash (<literal>\</literal>) to help reduce the need for backslash
|
|
doubling </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\c</literal><replaceable>X</replaceable> </entry>
|
|
<entry> (where <replaceable>X</replaceable> is any character) the character whose
|
|
low-order 5 bits are the same as those of
|
|
<replaceable>X</replaceable>, and whose other bits are all zero </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\e</literal> </entry>
|
|
<entry> the character whose collating-sequence name
|
|
is <literal>ESC</literal>,
|
|
or failing that, the character with octal value <literal>033</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\f</literal> </entry>
|
|
<entry> form feed, as in C </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\n</literal> </entry>
|
|
<entry> newline, as in C </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\r</literal> </entry>
|
|
<entry> carriage return, as in C </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\t</literal> </entry>
|
|
<entry> horizontal tab, as in C </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\u</literal><replaceable>wxyz</replaceable> </entry>
|
|
<entry> (where <replaceable>wxyz</replaceable> is exactly four hexadecimal digits)
|
|
the character whose hexadecimal value is
|
|
<literal>0x</literal><replaceable>wxyz</replaceable>
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\U</literal><replaceable>stuvwxyz</replaceable> </entry>
|
|
<entry> (where <replaceable>stuvwxyz</replaceable> is exactly eight hexadecimal
|
|
digits)
|
|
the character whose hexadecimal value is
|
|
<literal>0x</literal><replaceable>stuvwxyz</replaceable>
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\v</literal> </entry>
|
|
<entry> vertical tab, as in C </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\x</literal><replaceable>hhh</replaceable> </entry>
|
|
<entry> (where <replaceable>hhh</replaceable> is any sequence of hexadecimal
|
|
digits)
|
|
the character whose hexadecimal value is
|
|
<literal>0x</literal><replaceable>hhh</replaceable>
|
|
(a single character no matter how many hexadecimal digits are used)
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\0</literal> </entry>
|
|
<entry> the character whose value is <literal>0</literal> (the null byte)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\</literal><replaceable>xy</replaceable> </entry>
|
|
<entry> (where <replaceable>xy</replaceable> is exactly two octal digits,
|
|
and is not a <firstterm>back reference</firstterm>)
|
|
the character whose octal value is
|
|
<literal>0</literal><replaceable>xy</replaceable> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\</literal><replaceable>xyz</replaceable> </entry>
|
|
<entry> (where <replaceable>xyz</replaceable> is exactly three octal digits,
|
|
and is not a <firstterm>back reference</firstterm>)
|
|
the character whose octal value is
|
|
<literal>0</literal><replaceable>xyz</replaceable> </entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Hexadecimal digits are <literal>0</literal>-<literal>9</literal>,
|
|
<literal>a</literal>-<literal>f</literal>, and <literal>A</literal>-<literal>F</literal>.
|
|
Octal digits are <literal>0</literal>-<literal>7</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
Numeric character-entry escapes specifying values outside the ASCII range
|
|
(0–127) have meanings dependent on the database encoding. When the
|
|
encoding is UTF-8, escape values are equivalent to Unicode code points,
|
|
for example <literal>\u1234</literal> means the character <literal>U+1234</literal>.
|
|
For other multibyte encodings, character-entry escapes usually just
|
|
specify the concatenation of the byte values for the character. If the
|
|
escape value does not correspond to any legal character in the database
|
|
encoding, no error will be raised, but it will never match any data.
|
|
</para>
|
|
|
|
<para>
|
|
The character-entry escapes are always taken as ordinary characters.
|
|
For example, <literal>\135</literal> is <literal>]</literal> in ASCII, but
|
|
<literal>\135</literal> does not terminate a bracket expression.
|
|
</para>
|
|
|
|
<table id="posix-class-shorthand-escapes-table">
|
|
<title>Regular Expression Class-Shorthand Escapes</title>
|
|
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Escape</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry> <literal>\d</literal> </entry>
|
|
<entry> matches any digit, like
|
|
<literal>[[:digit:]]</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\s</literal> </entry>
|
|
<entry> matches any whitespace character, like
|
|
<literal>[[:space:]]</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\w</literal> </entry>
|
|
<entry> matches any word character, like
|
|
<literal>[[:word:]]</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\D</literal> </entry>
|
|
<entry> matches any non-digit, like
|
|
<literal>[^[:digit:]]</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\S</literal> </entry>
|
|
<entry> matches any non-whitespace character, like
|
|
<literal>[^[:space:]]</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\W</literal> </entry>
|
|
<entry> matches any non-word character, like
|
|
<literal>[^[:word:]]</literal> </entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The class-shorthand escapes also work within bracket expressions,
|
|
although the definitions shown above are not quite syntactically
|
|
valid in that context.
|
|
For example, <literal>[a-c\d]</literal> is equivalent to
|
|
<literal>[a-c[:digit:]]</literal>.
|
|
</para>
|
|
|
|
<table id="posix-constraint-escapes-table">
|
|
<title>Regular Expression Constraint Escapes</title>
|
|
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Escape</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry> <literal>\A</literal> </entry>
|
|
<entry> matches only at the beginning of the string
|
|
(see <xref linkend="posix-matching-rules"/> for how this differs from
|
|
<literal>^</literal>) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\m</literal> </entry>
|
|
<entry> matches only at the beginning of a word </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\M</literal> </entry>
|
|
<entry> matches only at the end of a word </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\y</literal> </entry>
|
|
<entry> matches only at the beginning or end of a word </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\Y</literal> </entry>
|
|
<entry> matches only at a point that is not the beginning or end of a
|
|
word </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\Z</literal> </entry>
|
|
<entry> matches only at the end of the string
|
|
(see <xref linkend="posix-matching-rules"/> for how this differs from
|
|
<literal>$</literal>) </entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
A word is defined as in the specification of
|
|
<literal>[[:<:]]</literal> and <literal>[[:>:]]</literal> above.
|
|
Constraint escapes are illegal within bracket expressions.
|
|
</para>
|
|
|
|
<table id="posix-constraint-backref-table">
|
|
<title>Regular Expression Back References</title>
|
|
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Escape</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry> <literal>\</literal><replaceable>m</replaceable> </entry>
|
|
<entry> (where <replaceable>m</replaceable> is a nonzero digit)
|
|
a back reference to the <replaceable>m</replaceable>'th subexpression </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>\</literal><replaceable>mnn</replaceable> </entry>
|
|
<entry> (where <replaceable>m</replaceable> is a nonzero digit, and
|
|
<replaceable>nn</replaceable> is some more digits, and the decimal value
|
|
<replaceable>mnn</replaceable> is not greater than the number of closing capturing
|
|
parentheses seen so far)
|
|
a back reference to the <replaceable>mnn</replaceable>'th subexpression </entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>
|
|
There is an inherent ambiguity between octal character-entry
|
|
escapes and back references, which is resolved by the following heuristics,
|
|
as hinted at above.
|
|
A leading zero always indicates an octal escape.
|
|
A single non-zero digit, not followed by another digit,
|
|
is always taken as a back reference.
|
|
A multi-digit sequence not starting with a zero is taken as a back
|
|
reference if it comes after a suitable subexpression
|
|
(i.e., the number is in the legal range for a back reference),
|
|
and otherwise is taken as octal.
|
|
</para>
|
|
</note>
|
|
</sect3>
|
|
|
|
<sect3 id="posix-metasyntax">
|
|
<title>Regular Expression Metasyntax</title>
|
|
|
|
<para>
|
|
In addition to the main syntax described above, there are some special
|
|
forms and miscellaneous syntactic facilities available.
|
|
</para>
|
|
|
|
<para>
|
|
An RE can begin with one of two special <firstterm>director</firstterm> prefixes.
|
|
If an RE begins with <literal>***:</literal>,
|
|
the rest of the RE is taken as an ARE. (This normally has no effect in
|
|
<productname>PostgreSQL</productname>, since REs are assumed to be AREs;
|
|
but it does have an effect if ERE or BRE mode had been specified by
|
|
the <replaceable>flags</replaceable> parameter to a regex function.)
|
|
If an RE begins with <literal>***=</literal>,
|
|
the rest of the RE is taken to be a literal string,
|
|
with all characters considered ordinary characters.
|
|
</para>
|
|
|
|
<para>
|
|
An ARE can begin with <firstterm>embedded options</firstterm>:
|
|
a sequence <literal>(?</literal><replaceable>xyz</replaceable><literal>)</literal>
|
|
(where <replaceable>xyz</replaceable> is one or more alphabetic characters)
|
|
specifies options affecting the rest of the RE.
|
|
These options override any previously determined options —
|
|
in particular, they can override the case-sensitivity behavior implied by
|
|
a regex operator, or the <replaceable>flags</replaceable> parameter to a regex
|
|
function.
|
|
The available option letters are
|
|
shown in <xref linkend="posix-embedded-options-table"/>.
|
|
Note that these same option letters are used in the <replaceable>flags</replaceable>
|
|
parameters of regex functions.
|
|
</para>
|
|
|
|
<table id="posix-embedded-options-table">
|
|
<title>ARE Embedded-Option Letters</title>
|
|
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Option</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry> <literal>b</literal> </entry>
|
|
<entry> rest of RE is a BRE </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>c</literal> </entry>
|
|
<entry> case-sensitive matching (overrides operator type) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>e</literal> </entry>
|
|
<entry> rest of RE is an ERE </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>i</literal> </entry>
|
|
<entry> case-insensitive matching (see
|
|
<xref linkend="posix-matching-rules"/>) (overrides operator type) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>m</literal> </entry>
|
|
<entry> historical synonym for <literal>n</literal> </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>n</literal> </entry>
|
|
<entry> newline-sensitive matching (see
|
|
<xref linkend="posix-matching-rules"/>) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>p</literal> </entry>
|
|
<entry> partial newline-sensitive matching (see
|
|
<xref linkend="posix-matching-rules"/>) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>q</literal> </entry>
|
|
<entry> rest of RE is a literal (<quote>quoted</quote>) string, all ordinary
|
|
characters </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>s</literal> </entry>
|
|
<entry> non-newline-sensitive matching (default) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>t</literal> </entry>
|
|
<entry> tight syntax (default; see below) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>w</literal> </entry>
|
|
<entry> inverse partial newline-sensitive (<quote>weird</quote>) matching
|
|
(see <xref linkend="posix-matching-rules"/>) </entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry> <literal>x</literal> </entry>
|
|
<entry> expanded syntax (see below) </entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Embedded options take effect at the <literal>)</literal> terminating the sequence.
|
|
They can appear only at the start of an ARE (after the
|
|
<literal>***:</literal> director if any).
|
|
</para>
|
|
|
|
<para>
|
|
In addition to the usual (<firstterm>tight</firstterm>) RE syntax, in which all
|
|
characters are significant, there is an <firstterm>expanded</firstterm> syntax,
|
|
available by specifying the embedded <literal>x</literal> option.
|
|
In the expanded syntax,
|
|
white-space characters in the RE are ignored, as are
|
|
all characters between a <literal>#</literal>
|
|
and the following newline (or the end of the RE). This
|
|
permits paragraphing and commenting a complex RE.
|
|
There are three exceptions to that basic rule:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
a white-space character or <literal>#</literal> preceded by <literal>\</literal> is
|
|
retained
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
white space or <literal>#</literal> within a bracket expression is retained
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
white space and comments cannot appear within multi-character symbols,
|
|
such as <literal>(?:</literal>
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
For this purpose, white-space characters are blank, tab, newline, and
|
|
any character that belongs to the <replaceable>space</replaceable> character class.
|
|
</para>
|
|
|
|
<para>
|
|
Finally, in an ARE, outside bracket expressions, the sequence
|
|
<literal>(?#</literal><replaceable>ttt</replaceable><literal>)</literal>
|
|
(where <replaceable>ttt</replaceable> is any text not containing a <literal>)</literal>)
|
|
is a comment, completely ignored.
|
|
Again, this is not allowed between the characters of
|
|
multi-character symbols, like <literal>(?:</literal>.
|
|
Such comments are more a historical artifact than a useful facility,
|
|
and their use is deprecated; use the expanded syntax instead.
|
|
</para>
|
|
|
|
<para>
|
|
<emphasis>None</emphasis> of these metasyntax extensions is available if
|
|
an initial <literal>***=</literal> director
|
|
has specified that the user's input be treated as a literal string
|
|
rather than as an RE.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="posix-matching-rules">
|
|
<title>Regular Expression Matching Rules</title>
|
|
|
|
<para>
|
|
In the event that an RE could match more than one substring of a given
|
|
string, the RE matches the one starting earliest in the string.
|
|
If the RE could match more than one substring starting at that point,
|
|
either the longest possible match or the shortest possible match will
|
|
be taken, depending on whether the RE is <firstterm>greedy</firstterm> or
|
|
<firstterm>non-greedy</firstterm>.
|
|
</para>
|
|
|
|
<para>
|
|
Whether an RE is greedy or not is determined by the following rules:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
Most atoms, and all constraints, have no greediness attribute (because
|
|
they cannot match variable amounts of text anyway).
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Adding parentheses around an RE does not change its greediness.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
A quantified atom with a fixed-repetition quantifier
|
|
(<literal>{</literal><replaceable>m</replaceable><literal>}</literal>
|
|
or
|
|
<literal>{</literal><replaceable>m</replaceable><literal>}?</literal>)
|
|
has the same greediness (possibly none) as the atom itself.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
A quantified atom with other normal quantifiers (including
|
|
<literal>{</literal><replaceable>m</replaceable><literal>,</literal><replaceable>n</replaceable><literal>}</literal>
|
|
with <replaceable>m</replaceable> equal to <replaceable>n</replaceable>)
|
|
is greedy (prefers longest match).
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
A quantified atom with a non-greedy quantifier (including
|
|
<literal>{</literal><replaceable>m</replaceable><literal>,</literal><replaceable>n</replaceable><literal>}?</literal>
|
|
with <replaceable>m</replaceable> equal to <replaceable>n</replaceable>)
|
|
is non-greedy (prefers shortest match).
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
A branch — that is, an RE that has no top-level
|
|
<literal>|</literal> operator — has the same greediness as the first
|
|
quantified atom in it that has a greediness attribute.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
An RE consisting of two or more branches connected by the
|
|
<literal>|</literal> operator is always greedy.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
The above rules associate greediness attributes not only with individual
|
|
quantified atoms, but with branches and entire REs that contain quantified
|
|
atoms. What that means is that the matching is done in such a way that
|
|
the branch, or whole RE, matches the longest or shortest possible
|
|
substring <emphasis>as a whole</emphasis>. Once the length of the entire match
|
|
is determined, the part of it that matches any particular subexpression
|
|
is determined on the basis of the greediness attribute of that
|
|
subexpression, with subexpressions starting earlier in the RE taking
|
|
priority over ones starting later.
|
|
</para>
|
|
|
|
<para>
|
|
An example of what this means:
|
|
<screen>
|
|
SELECT SUBSTRING('XY1234Z', 'Y*([0-9]{1,3})');
|
|
<lineannotation>Result: </lineannotation><computeroutput>123</computeroutput>
|
|
SELECT SUBSTRING('XY1234Z', 'Y*?([0-9]{1,3})');
|
|
<lineannotation>Result: </lineannotation><computeroutput>1</computeroutput>
|
|
</screen>
|
|
In the first case, the RE as a whole is greedy because <literal>Y*</literal>
|
|
is greedy. It can match beginning at the <literal>Y</literal>, and it matches
|
|
the longest possible string starting there, i.e., <literal>Y123</literal>.
|
|
The output is the parenthesized part of that, or <literal>123</literal>.
|
|
In the second case, the RE as a whole is non-greedy because <literal>Y*?</literal>
|
|
is non-greedy. It can match beginning at the <literal>Y</literal>, and it matches
|
|
the shortest possible string starting there, i.e., <literal>Y1</literal>.
|
|
The subexpression <literal>[0-9]{1,3}</literal> is greedy but it cannot change
|
|
the decision as to the overall match length; so it is forced to match
|
|
just <literal>1</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
In short, when an RE contains both greedy and non-greedy subexpressions,
|
|
the total match length is either as long as possible or as short as
|
|
possible, according to the attribute assigned to the whole RE. The
|
|
attributes assigned to the subexpressions only affect how much of that
|
|
match they are allowed to <quote>eat</quote> relative to each other.
|
|
</para>
|
|
|
|
<para>
|
|
The quantifiers <literal>{1,1}</literal> and <literal>{1,1}?</literal>
|
|
can be used to force greediness or non-greediness, respectively,
|
|
on a subexpression or a whole RE.
|
|
This is useful when you need the whole RE to have a greediness attribute
|
|
different from what's deduced from its elements. As an example,
|
|
suppose that we are trying to separate a string containing some digits
|
|
into the digits and the parts before and after them. We might try to
|
|
do that like this:
|
|
<screen>
|
|
SELECT regexp_match('abc01234xyz', '(.*)(\d+)(.*)');
|
|
<lineannotation>Result: </lineannotation><computeroutput>{abc0123,4,xyz}</computeroutput>
|
|
</screen>
|
|
That didn't work: the first <literal>.*</literal> is greedy so
|
|
it <quote>eats</quote> as much as it can, leaving the <literal>\d+</literal> to
|
|
match at the last possible place, the last digit. We might try to fix
|
|
that by making it non-greedy:
|
|
<screen>
|
|
SELECT regexp_match('abc01234xyz', '(.*?)(\d+)(.*)');
|
|
<lineannotation>Result: </lineannotation><computeroutput>{abc,0,""}</computeroutput>
|
|
</screen>
|
|
That didn't work either, because now the RE as a whole is non-greedy
|
|
and so it ends the overall match as soon as possible. We can get what
|
|
we want by forcing the RE as a whole to be greedy:
|
|
<screen>
|
|
SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
|
|
<lineannotation>Result: </lineannotation><computeroutput>{abc,01234,xyz}</computeroutput>
|
|
</screen>
|
|
Controlling the RE's overall greediness separately from its components'
|
|
greediness allows great flexibility in handling variable-length patterns.
|
|
</para>
|
|
|
|
<para>
|
|
When deciding what is a longer or shorter match,
|
|
match lengths are measured in characters, not collating elements.
|
|
An empty string is considered longer than no match at all.
|
|
For example:
|
|
<literal>bb*</literal>
|
|
matches the three middle characters of <literal>abbbc</literal>;
|
|
<literal>(week|wee)(night|knights)</literal>
|
|
matches all ten characters of <literal>weeknights</literal>;
|
|
when <literal>(.*).*</literal>
|
|
is matched against <literal>abc</literal> the parenthesized subexpression
|
|
matches all three characters; and when
|
|
<literal>(a*)*</literal> is matched against <literal>bc</literal>
|
|
both the whole RE and the parenthesized
|
|
subexpression match an empty string.
|
|
</para>
|
|
|
|
<para>
|
|
If case-independent matching is specified,
|
|
the effect is much as if all case distinctions had vanished from the
|
|
alphabet.
|
|
When an alphabetic that exists in multiple cases appears as an
|
|
ordinary character outside a bracket expression, it is effectively
|
|
transformed into a bracket expression containing both cases,
|
|
e.g., <literal>x</literal> becomes <literal>[xX]</literal>.
|
|
When it appears inside a bracket expression, all case counterparts
|
|
of it are added to the bracket expression, e.g.,
|
|
<literal>[x]</literal> becomes <literal>[xX]</literal>
|
|
and <literal>[^x]</literal> becomes <literal>[^xX]</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
If newline-sensitive matching is specified, <literal>.</literal>
|
|
and bracket expressions using <literal>^</literal>
|
|
will never match the newline character
|
|
(so that matches will not cross lines unless the RE
|
|
explicitly includes a newline)
|
|
and <literal>^</literal> and <literal>$</literal>
|
|
will match the empty string after and before a newline
|
|
respectively, in addition to matching at beginning and end of string
|
|
respectively.
|
|
But the ARE escapes <literal>\A</literal> and <literal>\Z</literal>
|
|
continue to match beginning or end of string <emphasis>only</emphasis>.
|
|
Also, the character class shorthands <literal>\D</literal>
|
|
and <literal>\W</literal> will match a newline regardless of this mode.
|
|
(Before <productname>PostgreSQL</productname> 14, they did not match
|
|
newlines when in newline-sensitive mode.
|
|
Write <literal>[^[:digit:]]</literal>
|
|
or <literal>[^[:word:]]</literal> to get the old behavior.)
|
|
</para>
|
|
|
|
<para>
|
|
If partial newline-sensitive matching is specified,
|
|
this affects <literal>.</literal> and bracket expressions
|
|
as with newline-sensitive matching, but not <literal>^</literal>
|
|
and <literal>$</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
If inverse partial newline-sensitive matching is specified,
|
|
this affects <literal>^</literal> and <literal>$</literal>
|
|
as with newline-sensitive matching, but not <literal>.</literal>
|
|
and bracket expressions.
|
|
This isn't very useful but is provided for symmetry.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="posix-limits-compatibility">
|
|
<title>Limits and Compatibility</title>
|
|
|
|
<para>
|
|
No particular limit is imposed on the length of REs in this
|
|
implementation. However,
|
|
programs intended to be highly portable should not employ REs longer
|
|
than 256 bytes,
|
|
as a POSIX-compliant implementation can refuse to accept such REs.
|
|
</para>
|
|
|
|
<para>
|
|
The only feature of AREs that is actually incompatible with
|
|
POSIX EREs is that <literal>\</literal> does not lose its special
|
|
significance inside bracket expressions.
|
|
All other ARE features use syntax which is illegal or has
|
|
undefined or unspecified effects in POSIX EREs;
|
|
the <literal>***</literal> syntax of directors likewise is outside the POSIX
|
|
syntax for both BREs and EREs.
|
|
</para>
|
|
|
|
<para>
|
|
Many of the ARE extensions are borrowed from Perl, but some have
|
|
been changed to clean them up, and a few Perl extensions are not present.
|
|
Incompatibilities of note include <literal>\b</literal>, <literal>\B</literal>,
|
|
the lack of special treatment for a trailing newline,
|
|
the addition of complemented bracket expressions to the things
|
|
affected by newline-sensitive matching,
|
|
the restrictions on parentheses and back references in lookahead/lookbehind
|
|
constraints, and the longest/shortest-match (rather than first-match)
|
|
matching semantics.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="posix-basic-regexes">
|
|
<title>Basic Regular Expressions</title>
|
|
|
|
<para>
|
|
BREs differ from EREs in several respects.
|
|
In BREs, <literal>|</literal>, <literal>+</literal>, and <literal>?</literal>
|
|
are ordinary characters and there is no equivalent
|
|
for their functionality.
|
|
The delimiters for bounds are
|
|
<literal>\{</literal> and <literal>\}</literal>,
|
|
with <literal>{</literal> and <literal>}</literal>
|
|
by themselves ordinary characters.
|
|
The parentheses for nested subexpressions are
|
|
<literal>\(</literal> and <literal>\)</literal>,
|
|
with <literal>(</literal> and <literal>)</literal> by themselves ordinary characters.
|
|
<literal>^</literal> is an ordinary character except at the beginning of the
|
|
RE or the beginning of a parenthesized subexpression,
|
|
<literal>$</literal> is an ordinary character except at the end of the
|
|
RE or the end of a parenthesized subexpression,
|
|
and <literal>*</literal> is an ordinary character if it appears at the beginning
|
|
of the RE or the beginning of a parenthesized subexpression
|
|
(after a possible leading <literal>^</literal>).
|
|
Finally, single-digit back references are available, and
|
|
<literal>\<</literal> and <literal>\></literal>
|
|
are synonyms for
|
|
<literal>[[:<:]]</literal> and <literal>[[:>:]]</literal>
|
|
respectively; no other escapes are available in BREs.
|
|
</para>
|
|
</sect3>
|
|
|
|
<!-- end re_syntax.n man page -->
|
|
|
|
<sect3 id="posix-vs-xquery">
|
|
<title>Differences from SQL Standard and XQuery</title>
|
|
|
|
<indexterm zone="posix-vs-xquery">
|
|
<primary>LIKE_REGEX</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="posix-vs-xquery">
|
|
<primary>OCCURRENCES_REGEX</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="posix-vs-xquery">
|
|
<primary>POSITION_REGEX</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="posix-vs-xquery">
|
|
<primary>SUBSTRING_REGEX</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="posix-vs-xquery">
|
|
<primary>TRANSLATE_REGEX</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="posix-vs-xquery">
|
|
<primary>XQuery regular expressions</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Since SQL:2008, the SQL standard includes regular expression operators
|
|
and functions that performs pattern
|
|
matching according to the XQuery regular expression
|
|
standard:
|
|
<itemizedlist>
|
|
<listitem><para><literal>LIKE_REGEX</literal></para></listitem>
|
|
<listitem><para><literal>OCCURRENCES_REGEX</literal></para></listitem>
|
|
<listitem><para><literal>POSITION_REGEX</literal></para></listitem>
|
|
<listitem><para><literal>SUBSTRING_REGEX</literal></para></listitem>
|
|
<listitem><para><literal>TRANSLATE_REGEX</literal></para></listitem>
|
|
</itemizedlist>
|
|
<productname>PostgreSQL</productname> does not currently implement these
|
|
operators and functions. You can get approximately equivalent
|
|
functionality in each case as shown in <xref
|
|
linkend="functions-regexp-sql-table"/>. (Various optional clauses on
|
|
both sides have been omitted in this table.)
|
|
</para>
|
|
|
|
<table id="functions-regexp-sql-table">
|
|
<title>Regular Expression Functions Equivalencies</title>
|
|
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>SQL standard</entry>
|
|
<entry><productname>PostgreSQL</productname></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><literal><replaceable>string</replaceable> LIKE_REGEX <replaceable>pattern</replaceable></literal></entry>
|
|
<entry><literal>regexp_like(<replaceable>string</replaceable>, <replaceable>pattern</replaceable>)</literal> or <literal><replaceable>string</replaceable> ~ <replaceable>pattern</replaceable></literal></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>OCCURRENCES_REGEX(<replaceable>pattern</replaceable> IN <replaceable>string</replaceable>)</literal></entry>
|
|
<entry><literal>regexp_count(<replaceable>string</replaceable>, <replaceable>pattern</replaceable>)</literal></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>POSITION_REGEX(<replaceable>pattern</replaceable> IN <replaceable>string</replaceable>)</literal></entry>
|
|
<entry><literal>regexp_instr(<replaceable>string</replaceable>, <replaceable>pattern</replaceable>)</literal></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>SUBSTRING_REGEX(<replaceable>pattern</replaceable> IN <replaceable>string</replaceable>)</literal></entry>
|
|
<entry><literal>regexp_substr(<replaceable>string</replaceable>, <replaceable>pattern</replaceable>)</literal></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>TRANSLATE_REGEX(<replaceable>pattern</replaceable> IN <replaceable>string</replaceable> WITH <replaceable>replacement</replaceable>)</literal></entry>
|
|
<entry><literal>regexp_replace(<replaceable>string</replaceable>, <replaceable>pattern</replaceable>, <replaceable>replacement</replaceable>)</literal></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Regular expression functions similar to those provided by PostgreSQL are
|
|
also available in a number of other SQL implementations, whereas the
|
|
SQL-standard functions are not as widely implemented. Some of the
|
|
details of the regular expression syntax will likely differ in each
|
|
implementation.
|
|
</para>
|
|
|
|
<para>
|
|
The SQL-standard operators and functions use XQuery regular expressions,
|
|
which are quite close to the ARE syntax described above.
|
|
Notable differences between the existing POSIX-based
|
|
regular-expression feature and XQuery regular expressions include:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
XQuery character class subtraction is not supported. An example of
|
|
this feature is using the following to match only English
|
|
consonants: <literal>[a-z-[aeiou]]</literal>.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
XQuery character class shorthands <literal>\c</literal>,
|
|
<literal>\C</literal>, <literal>\i</literal>,
|
|
and <literal>\I</literal> are not supported.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
XQuery character class elements
|
|
using <literal>\p{UnicodeProperty}</literal> or the
|
|
inverse <literal>\P{UnicodeProperty}</literal> are not supported.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
POSIX interprets character classes such as <literal>\w</literal>
|
|
(see <xref linkend="posix-class-shorthand-escapes-table"/>)
|
|
according to the prevailing locale (which you can control by
|
|
attaching a <literal>COLLATE</literal> clause to the operator or
|
|
function). XQuery specifies these classes by reference to Unicode
|
|
character properties, so equivalent behavior is obtained only with
|
|
a locale that follows the Unicode rules.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
The SQL standard (not XQuery itself) attempts to cater for more
|
|
variants of <quote>newline</quote> than POSIX does. The
|
|
newline-sensitive matching options described above consider only
|
|
ASCII NL (<literal>\n</literal>) to be a newline, but SQL would have
|
|
us treat CR (<literal>\r</literal>), CRLF (<literal>\r\n</literal>)
|
|
(a Windows-style newline), and some Unicode-only characters like
|
|
LINE SEPARATOR (U+2028) as newlines as well.
|
|
Notably, <literal>.</literal> and <literal>\s</literal> should
|
|
count <literal>\r\n</literal> as one character not two according to
|
|
SQL.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Of the character-entry escapes described in
|
|
<xref linkend="posix-character-entry-escapes-table"/>,
|
|
XQuery supports only <literal>\n</literal>, <literal>\r</literal>,
|
|
and <literal>\t</literal>.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
XQuery does not support
|
|
the <literal>[:<replaceable>name</replaceable>:]</literal> syntax
|
|
for character classes within bracket expressions.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
XQuery does not have lookahead or lookbehind constraints,
|
|
nor any of the constraint escapes described in
|
|
<xref linkend="posix-constraint-escapes-table"/>.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
The metasyntax forms described in <xref linkend="posix-metasyntax"/>
|
|
do not exist in XQuery.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
The regular expression flag letters defined by XQuery are
|
|
related to but not the same as the option letters for POSIX
|
|
(<xref linkend="posix-embedded-options-table"/>). While the
|
|
<literal>i</literal> and <literal>q</literal> options behave the
|
|
same, others do not:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
XQuery's <literal>s</literal> (allow dot to match newline)
|
|
and <literal>m</literal> (allow <literal>^</literal>
|
|
and <literal>$</literal> to match at newlines) flags provide
|
|
access to the same behaviors as
|
|
POSIX's <literal>n</literal>, <literal>p</literal>
|
|
and <literal>w</literal> flags, but they
|
|
do <emphasis>not</emphasis> match the behavior of
|
|
POSIX's <literal>s</literal> and <literal>m</literal> flags.
|
|
Note in particular that dot-matches-newline is the default
|
|
behavior in POSIX but not XQuery.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
XQuery's <literal>x</literal> (ignore whitespace in pattern) flag
|
|
is noticeably different from POSIX's expanded-mode flag.
|
|
POSIX's <literal>x</literal> flag also
|
|
allows <literal>#</literal> to begin a comment in the pattern,
|
|
and POSIX will not ignore a whitespace character after a
|
|
backslash.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
</sect3>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-formatting">
|
|
<title>Data Type Formatting Functions</title>
|
|
|
|
<indexterm>
|
|
<primary>formatting</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <productname>PostgreSQL</productname> formatting functions
|
|
provide a powerful set of tools for converting various data types
|
|
(date/time, integer, floating point, numeric) to formatted strings
|
|
and for converting from formatted strings to specific data types.
|
|
<xref linkend="functions-formatting-table"/> lists them.
|
|
These functions all follow a common calling convention: the first
|
|
argument is the value to be formatted and the second argument is a
|
|
template that defines the output or input format.
|
|
</para>
|
|
|
|
<table id="functions-formatting-table">
|
|
<title>Formatting Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_char</primary>
|
|
</indexterm>
|
|
<function>to_char</function> ( <type>timestamp</type>, <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>to_char</function> ( <type>timestamp with time zone</type>, <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts time stamp to string according to the given format.
|
|
</para>
|
|
<para>
|
|
<literal>to_char(timestamp '2002-04-20 17:31:12.66', 'HH12:MI:SS')</literal>
|
|
<returnvalue>05:31:12</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>to_char</function> ( <type>interval</type>, <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts interval to string according to the given format.
|
|
</para>
|
|
<para>
|
|
<literal>to_char(interval '15h 2m 12s', 'HH24:MI:SS')</literal>
|
|
<returnvalue>15:02:12</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>to_char</function> ( <replaceable>numeric_type</replaceable>, <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts number to string according to the given format; available
|
|
for <type>integer</type>, <type>bigint</type>, <type>numeric</type>,
|
|
<type>real</type>, <type>double precision</type>.
|
|
</para>
|
|
<para>
|
|
<literal>to_char(125, '999')</literal>
|
|
<returnvalue>125</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>to_char(125.8::real, '999D9')</literal>
|
|
<returnvalue>125.8</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>to_char(-125.8, '999D99S')</literal>
|
|
<returnvalue>125.80-</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_date</primary>
|
|
</indexterm>
|
|
<function>to_date</function> ( <type>text</type>, <type>text</type> )
|
|
<returnvalue>date</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts string to date according to the given format.
|
|
</para>
|
|
<para>
|
|
<literal>to_date('05 Dec 2000', 'DD Mon YYYY')</literal>
|
|
<returnvalue>2000-12-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_number</primary>
|
|
</indexterm>
|
|
<function>to_number</function> ( <type>text</type>, <type>text</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts string to numeric according to the given format.
|
|
</para>
|
|
<para>
|
|
<literal>to_number('12,454.8-', '99G999D9S')</literal>
|
|
<returnvalue>-12454.8</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_timestamp</primary>
|
|
</indexterm>
|
|
<function>to_timestamp</function> ( <type>text</type>, <type>text</type> )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts string to time stamp according to the given format.
|
|
(See also <function>to_timestamp(double precision)</function> in
|
|
<xref linkend="functions-datetime-table"/>.)
|
|
</para>
|
|
<para>
|
|
<literal>to_timestamp('05 Dec 2000', 'DD Mon YYYY')</literal>
|
|
<returnvalue>2000-12-05 00:00:00-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<tip>
|
|
<para>
|
|
<function>to_timestamp</function> and <function>to_date</function>
|
|
exist to handle input formats that cannot be converted by
|
|
simple casting. For most standard date/time formats, simply casting the
|
|
source string to the required data type works, and is much easier.
|
|
Similarly, <function>to_number</function> is unnecessary for standard numeric
|
|
representations.
|
|
</para>
|
|
</tip>
|
|
|
|
<para>
|
|
In a <function>to_char</function> output template string, there are certain
|
|
patterns that are recognized and replaced with appropriately-formatted
|
|
data based on the given value. Any text that is not a template pattern is
|
|
simply copied verbatim. Similarly, in an input template string (for the
|
|
other functions), template patterns identify the values to be supplied by
|
|
the input data string. If there are characters in the template string
|
|
that are not template patterns, the corresponding characters in the input
|
|
data string are simply skipped over (whether or not they are equal to the
|
|
template string characters).
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="functions-formatting-datetime-table"/> shows the
|
|
template patterns available for formatting date and time values.
|
|
</para>
|
|
|
|
<table id="functions-formatting-datetime-table">
|
|
<title>Template Patterns for Date/Time Formatting</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Pattern</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>HH</literal></entry>
|
|
<entry>hour of day (01–12)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>HH12</literal></entry>
|
|
<entry>hour of day (01–12)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>HH24</literal></entry>
|
|
<entry>hour of day (00–23)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>MI</literal></entry>
|
|
<entry>minute (00–59)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SS</literal></entry>
|
|
<entry>second (00–59)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>MS</literal></entry>
|
|
<entry>millisecond (000–999)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>US</literal></entry>
|
|
<entry>microsecond (000000–999999)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>FF1</literal></entry>
|
|
<entry>tenth of second (0–9)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>FF2</literal></entry>
|
|
<entry>hundredth of second (00–99)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>FF3</literal></entry>
|
|
<entry>millisecond (000–999)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>FF4</literal></entry>
|
|
<entry>tenth of a millisecond (0000–9999)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>FF5</literal></entry>
|
|
<entry>hundredth of a millisecond (00000–99999)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>FF6</literal></entry>
|
|
<entry>microsecond (000000–999999)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SSSS</literal>, <literal>SSSSS</literal></entry>
|
|
<entry>seconds past midnight (0–86399)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>AM</literal>, <literal>am</literal>,
|
|
<literal>PM</literal> or <literal>pm</literal></entry>
|
|
<entry>meridiem indicator (without periods)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>A.M.</literal>, <literal>a.m.</literal>,
|
|
<literal>P.M.</literal> or <literal>p.m.</literal></entry>
|
|
<entry>meridiem indicator (with periods)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>Y,YYY</literal></entry>
|
|
<entry>year (4 or more digits) with comma</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>YYYY</literal></entry>
|
|
<entry>year (4 or more digits)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>YYY</literal></entry>
|
|
<entry>last 3 digits of year</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>YY</literal></entry>
|
|
<entry>last 2 digits of year</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>Y</literal></entry>
|
|
<entry>last digit of year</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>IYYY</literal></entry>
|
|
<entry>ISO 8601 week-numbering year (4 or more digits)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>IYY</literal></entry>
|
|
<entry>last 3 digits of ISO 8601 week-numbering year</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>IY</literal></entry>
|
|
<entry>last 2 digits of ISO 8601 week-numbering year</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>I</literal></entry>
|
|
<entry>last digit of ISO 8601 week-numbering year</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>BC</literal>, <literal>bc</literal>,
|
|
<literal>AD</literal> or <literal>ad</literal></entry>
|
|
<entry>era indicator (without periods)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>B.C.</literal>, <literal>b.c.</literal>,
|
|
<literal>A.D.</literal> or <literal>a.d.</literal></entry>
|
|
<entry>era indicator (with periods)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>MONTH</literal></entry>
|
|
<entry>full upper case month name (blank-padded to 9 chars)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>Month</literal></entry>
|
|
<entry>full capitalized month name (blank-padded to 9 chars)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>month</literal></entry>
|
|
<entry>full lower case month name (blank-padded to 9 chars)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>MON</literal></entry>
|
|
<entry>abbreviated upper case month name (3 chars in English, localized lengths vary)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>Mon</literal></entry>
|
|
<entry>abbreviated capitalized month name (3 chars in English, localized lengths vary)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>mon</literal></entry>
|
|
<entry>abbreviated lower case month name (3 chars in English, localized lengths vary)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>MM</literal></entry>
|
|
<entry>month number (01–12)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>DAY</literal></entry>
|
|
<entry>full upper case day name (blank-padded to 9 chars)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>Day</literal></entry>
|
|
<entry>full capitalized day name (blank-padded to 9 chars)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>day</literal></entry>
|
|
<entry>full lower case day name (blank-padded to 9 chars)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>DY</literal></entry>
|
|
<entry>abbreviated upper case day name (3 chars in English, localized lengths vary)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>Dy</literal></entry>
|
|
<entry>abbreviated capitalized day name (3 chars in English, localized lengths vary)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>dy</literal></entry>
|
|
<entry>abbreviated lower case day name (3 chars in English, localized lengths vary)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>DDD</literal></entry>
|
|
<entry>day of year (001–366)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>IDDD</literal></entry>
|
|
<entry>day of ISO 8601 week-numbering year (001–371; day 1 of the year is Monday of the first ISO week)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>DD</literal></entry>
|
|
<entry>day of month (01–31)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>D</literal></entry>
|
|
<entry>day of the week, Sunday (<literal>1</literal>) to Saturday (<literal>7</literal>)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>ID</literal></entry>
|
|
<entry>ISO 8601 day of the week, Monday (<literal>1</literal>) to Sunday (<literal>7</literal>)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>W</literal></entry>
|
|
<entry>week of month (1–5) (the first week starts on the first day of the month)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WW</literal></entry>
|
|
<entry>week number of year (1–53) (the first week starts on the first day of the year)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>IW</literal></entry>
|
|
<entry>week number of ISO 8601 week-numbering year (01–53; the first Thursday of the year is in week 1)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>CC</literal></entry>
|
|
<entry>century (2 digits) (the twenty-first century starts on 2001-01-01)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>J</literal></entry>
|
|
<entry>Julian Date (integer days since November 24, 4714 BC at local
|
|
midnight; see <xref linkend="datetime-julian-dates"/>)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>Q</literal></entry>
|
|
<entry>quarter</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>RM</literal></entry>
|
|
<entry>month in upper case Roman numerals (I–XII; I=January)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>rm</literal></entry>
|
|
<entry>month in lower case Roman numerals (i–xii; i=January)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>TZ</literal></entry>
|
|
<entry>upper case time-zone abbreviation</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>tz</literal></entry>
|
|
<entry>lower case time-zone abbreviation</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>TZH</literal></entry>
|
|
<entry>time-zone hours</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>TZM</literal></entry>
|
|
<entry>time-zone minutes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>OF</literal></entry>
|
|
<entry>time-zone offset from UTC (<replaceable>HH</replaceable>
|
|
or <replaceable>HH</replaceable><literal>:</literal><replaceable>MM</replaceable>)</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Modifiers can be applied to any template pattern to alter its
|
|
behavior. For example, <literal>FMMonth</literal>
|
|
is the <literal>Month</literal> pattern with the
|
|
<literal>FM</literal> modifier.
|
|
<xref linkend="functions-formatting-datetimemod-table"/> shows the
|
|
modifier patterns for date/time formatting.
|
|
</para>
|
|
|
|
<table id="functions-formatting-datetimemod-table">
|
|
<title>Template Pattern Modifiers for Date/Time Formatting</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Modifier</entry>
|
|
<entry>Description</entry>
|
|
<entry>Example</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>FM</literal> prefix</entry>
|
|
<entry>fill mode (suppress leading zeroes and padding blanks)</entry>
|
|
<entry><literal>FMMonth</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>TH</literal> suffix</entry>
|
|
<entry>upper case ordinal number suffix</entry>
|
|
<entry><literal>DDTH</literal>, e.g., <literal>12TH</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>th</literal> suffix</entry>
|
|
<entry>lower case ordinal number suffix</entry>
|
|
<entry><literal>DDth</literal>, e.g., <literal>12th</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>FX</literal> prefix</entry>
|
|
<entry>fixed format global option (see usage notes)</entry>
|
|
<entry><literal>FX Month DD Day</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>TM</literal> prefix</entry>
|
|
<entry>translation mode (use localized day and month names based on
|
|
<xref linkend="guc-lc-time"/>)</entry>
|
|
<entry><literal>TMMonth</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SP</literal> suffix</entry>
|
|
<entry>spell mode (not implemented)</entry>
|
|
<entry><literal>DDSP</literal></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Usage notes for date/time formatting:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
<literal>FM</literal> suppresses leading zeroes and trailing blanks
|
|
that would otherwise be added to make the output of a pattern be
|
|
fixed-width. In <productname>PostgreSQL</productname>,
|
|
<literal>FM</literal> modifies only the next specification, while in
|
|
Oracle <literal>FM</literal> affects all subsequent
|
|
specifications, and repeated <literal>FM</literal> modifiers
|
|
toggle fill mode on and off.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<literal>TM</literal> suppresses trailing blanks whether or
|
|
not <literal>FM</literal> is specified.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>to_timestamp</function> and <function>to_date</function>
|
|
ignore letter case in the input; so for
|
|
example <literal>MON</literal>, <literal>Mon</literal>,
|
|
and <literal>mon</literal> all accept the same strings. When using
|
|
the <literal>TM</literal> modifier, case-folding is done according to
|
|
the rules of the function's input collation (see
|
|
<xref linkend="collation"/>).
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>to_timestamp</function> and <function>to_date</function>
|
|
skip multiple blank spaces at the beginning of the input string and
|
|
around date and time values unless the <literal>FX</literal> option is used. For example,
|
|
<literal>to_timestamp(' 2000 JUN', 'YYYY MON')</literal> and
|
|
<literal>to_timestamp('2000 - JUN', 'YYYY-MON')</literal> work, but
|
|
<literal>to_timestamp('2000 JUN', 'FXYYYY MON')</literal> returns an error
|
|
because <function>to_timestamp</function> expects only a single space.
|
|
<literal>FX</literal> must be specified as the first item in
|
|
the template.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
A separator (a space or non-letter/non-digit character) in the template string of
|
|
<function>to_timestamp</function> and <function>to_date</function>
|
|
matches any single separator in the input string or is skipped,
|
|
unless the <literal>FX</literal> option is used.
|
|
For example, <literal>to_timestamp('2000JUN', 'YYYY///MON')</literal> and
|
|
<literal>to_timestamp('2000/JUN', 'YYYY MON')</literal> work, but
|
|
<literal>to_timestamp('2000//JUN', 'YYYY/MON')</literal>
|
|
returns an error because the number of separators in the input string
|
|
exceeds the number of separators in the template.
|
|
</para>
|
|
<para>
|
|
If <literal>FX</literal> is specified, a separator in the template string
|
|
matches exactly one character in the input string. But note that the
|
|
input string character is not required to be the same as the separator from the template string.
|
|
For example, <literal>to_timestamp('2000/JUN', 'FXYYYY MON')</literal>
|
|
works, but <literal>to_timestamp('2000/JUN', 'FXYYYY MON')</literal>
|
|
returns an error because the second space in the template string consumes
|
|
the letter <literal>J</literal> from the input string.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
A <literal>TZH</literal> template pattern can match a signed number.
|
|
Without the <literal>FX</literal> option, minus signs may be ambiguous,
|
|
and could be interpreted as a separator.
|
|
This ambiguity is resolved as follows: If the number of separators before
|
|
<literal>TZH</literal> in the template string is less than the number of
|
|
separators before the minus sign in the input string, the minus sign
|
|
is interpreted as part of <literal>TZH</literal>.
|
|
Otherwise, the minus sign is considered to be a separator between values.
|
|
For example, <literal>to_timestamp('2000 -10', 'YYYY TZH')</literal> matches
|
|
<literal>-10</literal> to <literal>TZH</literal>, but
|
|
<literal>to_timestamp('2000 -10', 'YYYY TZH')</literal>
|
|
matches <literal>10</literal> to <literal>TZH</literal>.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
Ordinary text is allowed in <function>to_char</function>
|
|
templates and will be output literally. You can put a substring
|
|
in double quotes to force it to be interpreted as literal text
|
|
even if it contains template patterns. For example, in
|
|
<literal>'"Hello Year "YYYY'</literal>, the <literal>YYYY</literal>
|
|
will be replaced by the year data, but the single <literal>Y</literal> in <literal>Year</literal>
|
|
will not be.
|
|
In <function>to_date</function>, <function>to_number</function>,
|
|
and <function>to_timestamp</function>, literal text and double-quoted
|
|
strings result in skipping the number of characters contained in the
|
|
string; for example <literal>"XX"</literal> skips two input characters
|
|
(whether or not they are <literal>XX</literal>).
|
|
</para>
|
|
<tip>
|
|
<para>
|
|
Prior to <productname>PostgreSQL</productname> 12, it was possible to
|
|
skip arbitrary text in the input string using non-letter or non-digit
|
|
characters. For example,
|
|
<literal>to_timestamp('2000y6m1d', 'yyyy-MM-DD')</literal> used to
|
|
work. Now you can only use letter characters for this purpose. For example,
|
|
<literal>to_timestamp('2000y6m1d', 'yyyytMMtDDt')</literal> and
|
|
<literal>to_timestamp('2000y6m1d', 'yyyy"y"MM"m"DD"d"')</literal>
|
|
skip <literal>y</literal>, <literal>m</literal>, and
|
|
<literal>d</literal>.
|
|
</para>
|
|
</tip>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
If you want to have a double quote in the output you must
|
|
precede it with a backslash, for example <literal>'\"YYYY
|
|
Month\"'</literal>. <!-- "" font-lock sanity :-) -->
|
|
Backslashes are not otherwise special outside of double-quoted
|
|
strings. Within a double-quoted string, a backslash causes the
|
|
next character to be taken literally, whatever it is (but this
|
|
has no special effect unless the next character is a double quote
|
|
or another backslash).
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
In <function>to_timestamp</function> and <function>to_date</function>,
|
|
if the year format specification is less than four digits, e.g.,
|
|
<literal>YYY</literal>, and the supplied year is less than four digits,
|
|
the year will be adjusted to be nearest to the year 2020, e.g.,
|
|
<literal>95</literal> becomes 1995.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
In <function>to_timestamp</function> and <function>to_date</function>,
|
|
negative years are treated as signifying BC. If you write both a
|
|
negative year and an explicit <literal>BC</literal> field, you get AD
|
|
again. An input of year zero is treated as 1 BC.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
In <function>to_timestamp</function> and <function>to_date</function>,
|
|
the <literal>YYYY</literal> conversion has a restriction when
|
|
processing years with more than 4 digits. You must
|
|
use some non-digit character or template after <literal>YYYY</literal>,
|
|
otherwise the year is always interpreted as 4 digits. For example
|
|
(with the year 20000):
|
|
<literal>to_date('200001130', 'YYYYMMDD')</literal> will be
|
|
interpreted as a 4-digit year; instead use a non-digit
|
|
separator after the year, like
|
|
<literal>to_date('20000-1130', 'YYYY-MMDD')</literal> or
|
|
<literal>to_date('20000Nov30', 'YYYYMonDD')</literal>.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
In <function>to_timestamp</function> and <function>to_date</function>,
|
|
the <literal>CC</literal> (century) field is accepted but ignored
|
|
if there is a <literal>YYY</literal>, <literal>YYYY</literal> or
|
|
<literal>Y,YYY</literal> field. If <literal>CC</literal> is used with
|
|
<literal>YY</literal> or <literal>Y</literal> then the result is
|
|
computed as that year in the specified century. If the century is
|
|
specified but the year is not, the first year of the century
|
|
is assumed.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
In <function>to_timestamp</function> and <function>to_date</function>,
|
|
weekday names or numbers (<literal>DAY</literal>, <literal>D</literal>,
|
|
and related field types) are accepted but are ignored for purposes of
|
|
computing the result. The same is true for quarter
|
|
(<literal>Q</literal>) fields.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
In <function>to_timestamp</function> and <function>to_date</function>,
|
|
an ISO 8601 week-numbering date (as distinct from a Gregorian date)
|
|
can be specified in one of two ways:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
Year, week number, and weekday: for
|
|
example <literal>to_date('2006-42-4', 'IYYY-IW-ID')</literal>
|
|
returns the date <literal>2006-10-19</literal>.
|
|
If you omit the weekday it is assumed to be 1 (Monday).
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Year and day of year: for example <literal>to_date('2006-291',
|
|
'IYYY-IDDD')</literal> also returns <literal>2006-10-19</literal>.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
<para>
|
|
Attempting to enter a date using a mixture of ISO 8601 week-numbering
|
|
fields and Gregorian date fields is nonsensical, and will cause an
|
|
error. In the context of an ISO 8601 week-numbering year, the
|
|
concept of a <quote>month</quote> or <quote>day of month</quote> has no
|
|
meaning. In the context of a Gregorian year, the ISO week has no
|
|
meaning.
|
|
</para>
|
|
<caution>
|
|
<para>
|
|
While <function>to_date</function> will reject a mixture of
|
|
Gregorian and ISO week-numbering date
|
|
fields, <function>to_char</function> will not, since output format
|
|
specifications like <literal>YYYY-MM-DD (IYYY-IDDD)</literal> can be
|
|
useful. But avoid writing something like <literal>IYYY-MM-DD</literal>;
|
|
that would yield surprising results near the start of the year.
|
|
(See <xref linkend="functions-datetime-extract"/> for more
|
|
information.)
|
|
</para>
|
|
</caution>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
In <function>to_timestamp</function>, millisecond
|
|
(<literal>MS</literal>) or microsecond (<literal>US</literal>)
|
|
fields are used as the
|
|
seconds digits after the decimal point. For example
|
|
<literal>to_timestamp('12.3', 'SS.MS')</literal> is not 3 milliseconds,
|
|
but 300, because the conversion treats it as 12 + 0.3 seconds.
|
|
So, for the format <literal>SS.MS</literal>, the input values
|
|
<literal>12.3</literal>, <literal>12.30</literal>,
|
|
and <literal>12.300</literal> specify the
|
|
same number of milliseconds. To get three milliseconds, one must write
|
|
<literal>12.003</literal>, which the conversion treats as
|
|
12 + 0.003 = 12.003 seconds.
|
|
</para>
|
|
|
|
<para>
|
|
Here is a more
|
|
complex example:
|
|
<literal>to_timestamp('15:12:02.020.001230', 'HH24:MI:SS.MS.US')</literal>
|
|
is 15 hours, 12 minutes, and 2 seconds + 20 milliseconds +
|
|
1230 microseconds = 2.021230 seconds.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>to_char(..., 'ID')</function>'s day of the week numbering
|
|
matches the <function>extract(isodow from ...)</function> function, but
|
|
<function>to_char(..., 'D')</function>'s does not match
|
|
<function>extract(dow from ...)</function>'s day numbering.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>to_char(interval)</function> formats <literal>HH</literal> and
|
|
<literal>HH12</literal> as shown on a 12-hour clock, for example zero hours
|
|
and 36 hours both output as <literal>12</literal>, while <literal>HH24</literal>
|
|
outputs the full hour value, which can exceed 23 in
|
|
an <type>interval</type> value.
|
|
</para>
|
|
</listitem>
|
|
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="functions-formatting-numeric-table"/> shows the
|
|
template patterns available for formatting numeric values.
|
|
</para>
|
|
|
|
<table id="functions-formatting-numeric-table">
|
|
<title>Template Patterns for Numeric Formatting</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Pattern</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>9</literal></entry>
|
|
<entry>digit position (can be dropped if insignificant)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>0</literal></entry>
|
|
<entry>digit position (will not be dropped, even if insignificant)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>.</literal> (period)</entry>
|
|
<entry>decimal point</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>,</literal> (comma)</entry>
|
|
<entry>group (thousands) separator</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>PR</literal></entry>
|
|
<entry>negative value in angle brackets</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>S</literal></entry>
|
|
<entry>sign anchored to number (uses locale)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>L</literal></entry>
|
|
<entry>currency symbol (uses locale)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>D</literal></entry>
|
|
<entry>decimal point (uses locale)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>G</literal></entry>
|
|
<entry>group separator (uses locale)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>MI</literal></entry>
|
|
<entry>minus sign in specified position (if number < 0)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>PL</literal></entry>
|
|
<entry>plus sign in specified position (if number > 0)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SG</literal></entry>
|
|
<entry>plus/minus sign in specified position</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>RN</literal></entry>
|
|
<entry>Roman numeral (input between 1 and 3999)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>TH</literal> or <literal>th</literal></entry>
|
|
<entry>ordinal number suffix</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>V</literal></entry>
|
|
<entry>shift specified number of digits (see notes)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EEEE</literal></entry>
|
|
<entry>exponent for scientific notation</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Usage notes for numeric formatting:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
<literal>0</literal> specifies a digit position that will always be printed,
|
|
even if it contains a leading/trailing zero. <literal>9</literal> also
|
|
specifies a digit position, but if it is a leading zero then it will
|
|
be replaced by a space, while if it is a trailing zero and fill mode
|
|
is specified then it will be deleted. (For <function>to_number()</function>,
|
|
these two pattern characters are equivalent.)
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
If the format provides fewer fractional digits than the number being
|
|
formatted, <function>to_char()</function> will round the number to
|
|
the specified number of fractional digits.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
The pattern characters <literal>S</literal>, <literal>L</literal>, <literal>D</literal>,
|
|
and <literal>G</literal> represent the sign, currency symbol, decimal point,
|
|
and thousands separator characters defined by the current locale
|
|
(see <xref linkend="guc-lc-monetary"/>
|
|
and <xref linkend="guc-lc-numeric"/>). The pattern characters period
|
|
and comma represent those exact characters, with the meanings of
|
|
decimal point and thousands separator, regardless of locale.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
If no explicit provision is made for a sign
|
|
in <function>to_char()</function>'s pattern, one column will be reserved for
|
|
the sign, and it will be anchored to (appear just left of) the
|
|
number. If <literal>S</literal> appears just left of some <literal>9</literal>'s,
|
|
it will likewise be anchored to the number.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
A sign formatted using <literal>SG</literal>, <literal>PL</literal>, or
|
|
<literal>MI</literal> is not anchored to
|
|
the number; for example,
|
|
<literal>to_char(-12, 'MI9999')</literal> produces <literal>'- 12'</literal>
|
|
but <literal>to_char(-12, 'S9999')</literal> produces <literal>' -12'</literal>.
|
|
(The Oracle implementation does not allow the use of
|
|
<literal>MI</literal> before <literal>9</literal>, but rather
|
|
requires that <literal>9</literal> precede
|
|
<literal>MI</literal>.)
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<literal>TH</literal> does not convert values less than zero
|
|
and does not convert fractional numbers.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<literal>PL</literal>, <literal>SG</literal>, and
|
|
<literal>TH</literal> are <productname>PostgreSQL</productname>
|
|
extensions.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
In <function>to_number</function>, if non-data template patterns such
|
|
as <literal>L</literal> or <literal>TH</literal> are used, the
|
|
corresponding number of input characters are skipped, whether or not
|
|
they match the template pattern, unless they are data characters
|
|
(that is, digits, sign, decimal point, or comma). For
|
|
example, <literal>TH</literal> would skip two non-data characters.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<literal>V</literal> with <function>to_char</function>
|
|
multiplies the input values by
|
|
<literal>10^<replaceable>n</replaceable></literal>, where
|
|
<replaceable>n</replaceable> is the number of digits following
|
|
<literal>V</literal>. <literal>V</literal> with
|
|
<function>to_number</function> divides in a similar manner.
|
|
<function>to_char</function> and <function>to_number</function>
|
|
do not support the use of
|
|
<literal>V</literal> combined with a decimal point
|
|
(e.g., <literal>99.9V99</literal> is not allowed).
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<literal>EEEE</literal> (scientific notation) cannot be used in
|
|
combination with any of the other formatting patterns or
|
|
modifiers other than digit and decimal point patterns, and must be at the end of the format string
|
|
(e.g., <literal>9.99EEEE</literal> is a valid pattern).
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
Certain modifiers can be applied to any template pattern to alter its
|
|
behavior. For example, <literal>FM99.99</literal>
|
|
is the <literal>99.99</literal> pattern with the
|
|
<literal>FM</literal> modifier.
|
|
<xref linkend="functions-formatting-numericmod-table"/> shows the
|
|
modifier patterns for numeric formatting.
|
|
</para>
|
|
|
|
<table id="functions-formatting-numericmod-table">
|
|
<title>Template Pattern Modifiers for Numeric Formatting</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Modifier</entry>
|
|
<entry>Description</entry>
|
|
<entry>Example</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>FM</literal> prefix</entry>
|
|
<entry>fill mode (suppress trailing zeroes and padding blanks)</entry>
|
|
<entry><literal>FM99.99</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>TH</literal> suffix</entry>
|
|
<entry>upper case ordinal number suffix</entry>
|
|
<entry><literal>999TH</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>th</literal> suffix</entry>
|
|
<entry>lower case ordinal number suffix</entry>
|
|
<entry><literal>999th</literal></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-formatting-examples-table"/> shows some
|
|
examples of the use of the <function>to_char</function> function.
|
|
</para>
|
|
|
|
<table id="functions-formatting-examples-table">
|
|
<title><function>to_char</function> Examples</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Expression</entry>
|
|
<entry>Result</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>to_char(current_timestamp, 'Day, DD HH12:MI:SS')</literal></entry>
|
|
<entry><literal>'Tuesday , 06 05:39:18'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(current_timestamp, 'FMDay, FMDD HH12:MI:SS')</literal></entry>
|
|
<entry><literal>'Tuesday, 6 05:39:18'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(current_timestamp AT TIME ZONE
|
|
'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')</literal></entry>
|
|
<entry><literal>'2022-12-06T05:39:18Z'</literal>,
|
|
<acronym>ISO</acronym> 8601 extended format</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(-0.1, '99.99')</literal></entry>
|
|
<entry><literal>' -.10'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(-0.1, 'FM9.99')</literal></entry>
|
|
<entry><literal>'-.1'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(-0.1, 'FM90.99')</literal></entry>
|
|
<entry><literal>'-0.1'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(0.1, '0.9')</literal></entry>
|
|
<entry><literal>' 0.1'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(12, '9990999.9')</literal></entry>
|
|
<entry><literal>' 0012.0'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(12, 'FM9990999.9')</literal></entry>
|
|
<entry><literal>'0012.'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, '999')</literal></entry>
|
|
<entry><literal>' 485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(-485, '999')</literal></entry>
|
|
<entry><literal>'-485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, '9 9 9')</literal></entry>
|
|
<entry><literal>' 4 8 5'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(1485, '9,999')</literal></entry>
|
|
<entry><literal>' 1,485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(1485, '9G999')</literal></entry>
|
|
<entry><literal>' 1 485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(148.5, '999.999')</literal></entry>
|
|
<entry><literal>' 148.500'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(148.5, 'FM999.999')</literal></entry>
|
|
<entry><literal>'148.5'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(148.5, 'FM999.990')</literal></entry>
|
|
<entry><literal>'148.500'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(148.5, '999D999')</literal></entry>
|
|
<entry><literal>' 148,500'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(3148.5, '9G999D999')</literal></entry>
|
|
<entry><literal>' 3 148,500'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(-485, '999S')</literal></entry>
|
|
<entry><literal>'485-'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(-485, '999MI')</literal></entry>
|
|
<entry><literal>'485-'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, '999MI')</literal></entry>
|
|
<entry><literal>'485 '</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, 'FM999MI')</literal></entry>
|
|
<entry><literal>'485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, 'PL999')</literal></entry>
|
|
<entry><literal>'+485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, 'SG999')</literal></entry>
|
|
<entry><literal>'+485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(-485, 'SG999')</literal></entry>
|
|
<entry><literal>'-485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(-485, '9SG99')</literal></entry>
|
|
<entry><literal>'4-85'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(-485, '999PR')</literal></entry>
|
|
<entry><literal>'<485>'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, 'L999')</literal></entry>
|
|
<entry><literal>'DM 485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, 'RN')</literal></entry>
|
|
<entry><literal>' CDLXXXV'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, 'FMRN')</literal></entry>
|
|
<entry><literal>'CDLXXXV'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(5.2, 'FMRN')</literal></entry>
|
|
<entry><literal>'V'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(482, '999th')</literal></entry>
|
|
<entry><literal>' 482nd'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485, '"Good number:"999')</literal></entry>
|
|
<entry><literal>'Good number: 485'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(485.8, '"Pre:"999" Post:" .999')</literal></entry>
|
|
<entry><literal>'Pre: 485 Post: .800'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(12, '99V999')</literal></entry>
|
|
<entry><literal>' 12000'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(12.4, '99V999')</literal></entry>
|
|
<entry><literal>' 12400'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(12.45, '99V9')</literal></entry>
|
|
<entry><literal>' 125'</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>to_char(0.0004859, '9.99EEEE')</literal></entry>
|
|
<entry><literal>' 4.86e-04'</literal></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-datetime">
|
|
<title>Date/Time Functions and Operators</title>
|
|
|
|
<para>
|
|
<xref linkend="functions-datetime-table"/> shows the available
|
|
functions for date/time value processing, with details appearing in
|
|
the following subsections. <xref
|
|
linkend="operators-datetime-table"/> illustrates the behaviors of
|
|
the basic arithmetic operators (<literal>+</literal>,
|
|
<literal>*</literal>, etc.). For formatting functions, refer to
|
|
<xref linkend="functions-formatting"/>. You should be familiar with
|
|
the background information on date/time data types from <xref
|
|
linkend="datatype-datetime"/>.
|
|
</para>
|
|
|
|
<para>
|
|
In addition, the usual comparison operators shown in
|
|
<xref linkend="functions-comparison-op-table"/> are available for the
|
|
date/time types. Dates and timestamps (with or without time zone) are
|
|
all comparable, while times (with or without time zone) and intervals
|
|
can only be compared to other values of the same data type. When
|
|
comparing a timestamp without time zone to a timestamp with time zone,
|
|
the former value is assumed to be given in the time zone specified by
|
|
the <xref linkend="guc-timezone"/> configuration parameter, and is
|
|
rotated to UTC for comparison to the latter value (which is already
|
|
in UTC internally). Similarly, a date value is assumed to represent
|
|
midnight in the <varname>TimeZone</varname> zone when comparing it
|
|
to a timestamp.
|
|
</para>
|
|
|
|
<para>
|
|
All the functions and operators described below that take <type>time</type> or <type>timestamp</type>
|
|
inputs actually come in two variants: one that takes <type>time with time zone</type> or <type>timestamp
|
|
with time zone</type>, and one that takes <type>time without time zone</type> or <type>timestamp without time zone</type>.
|
|
For brevity, these variants are not shown separately. Also, the
|
|
<literal>+</literal> and <literal>*</literal> operators come in commutative pairs (for
|
|
example both <type>date</type> <literal>+</literal> <type>integer</type>
|
|
and <type>integer</type> <literal>+</literal> <type>date</type>); we show
|
|
only one of each such pair.
|
|
</para>
|
|
|
|
<table id="operators-datetime-table">
|
|
<title>Date/Time Operators</title>
|
|
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>date</type> <literal>+</literal> <type>integer</type>
|
|
<returnvalue>date</returnvalue>
|
|
</para>
|
|
<para>
|
|
Add a number of days to a date
|
|
</para>
|
|
<para>
|
|
<literal>date '2001-09-28' + 7</literal>
|
|
<returnvalue>2001-10-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>date</type> <literal>+</literal> <type>interval</type>
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Add an interval to a date
|
|
</para>
|
|
<para>
|
|
<literal>date '2001-09-28' + interval '1 hour'</literal>
|
|
<returnvalue>2001-09-28 01:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>date</type> <literal>+</literal> <type>time</type>
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Add a time-of-day to a date
|
|
</para>
|
|
<para>
|
|
<literal>date '2001-09-28' + time '03:00'</literal>
|
|
<returnvalue>2001-09-28 03:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>interval</type> <literal>+</literal> <type>interval</type>
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Add intervals
|
|
</para>
|
|
<para>
|
|
<literal>interval '1 day' + interval '1 hour'</literal>
|
|
<returnvalue>1 day 01:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>timestamp</type> <literal>+</literal> <type>interval</type>
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Add an interval to a timestamp
|
|
</para>
|
|
<para>
|
|
<literal>timestamp '2001-09-28 01:00' + interval '23 hours'</literal>
|
|
<returnvalue>2001-09-29 00:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>time</type> <literal>+</literal> <type>interval</type>
|
|
<returnvalue>time</returnvalue>
|
|
</para>
|
|
<para>
|
|
Add an interval to a time
|
|
</para>
|
|
<para>
|
|
<literal>time '01:00' + interval '3 hours'</literal>
|
|
<returnvalue>04:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>-</literal> <type>interval</type>
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Negate an interval
|
|
</para>
|
|
<para>
|
|
<literal>- interval '23 hours'</literal>
|
|
<returnvalue>-23:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>date</type> <literal>-</literal> <type>date</type>
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract dates, producing the number of days elapsed
|
|
</para>
|
|
<para>
|
|
<literal>date '2001-10-01' - date '2001-09-28'</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>date</type> <literal>-</literal> <type>integer</type>
|
|
<returnvalue>date</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract a number of days from a date
|
|
</para>
|
|
<para>
|
|
<literal>date '2001-10-01' - 7</literal>
|
|
<returnvalue>2001-09-24</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>date</type> <literal>-</literal> <type>interval</type>
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract an interval from a date
|
|
</para>
|
|
<para>
|
|
<literal>date '2001-09-28' - interval '1 hour'</literal>
|
|
<returnvalue>2001-09-27 23:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>time</type> <literal>-</literal> <type>time</type>
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract times
|
|
</para>
|
|
<para>
|
|
<literal>time '05:00' - time '03:00'</literal>
|
|
<returnvalue>02:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>time</type> <literal>-</literal> <type>interval</type>
|
|
<returnvalue>time</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract an interval from a time
|
|
</para>
|
|
<para>
|
|
<literal>time '05:00' - interval '2 hours'</literal>
|
|
<returnvalue>03:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>timestamp</type> <literal>-</literal> <type>interval</type>
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract an interval from a timestamp
|
|
</para>
|
|
<para>
|
|
<literal>timestamp '2001-09-28 23:00' - interval '23 hours'</literal>
|
|
<returnvalue>2001-09-28 00:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>interval</type> <literal>-</literal> <type>interval</type>
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract intervals
|
|
</para>
|
|
<para>
|
|
<literal>interval '1 day' - interval '1 hour'</literal>
|
|
<returnvalue>1 day -01:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>timestamp</type> <literal>-</literal> <type>timestamp</type>
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract timestamps (converting 24-hour intervals into days,
|
|
similarly to <link
|
|
linkend="function-justify-hours"><function>justify_hours()</function></link>)
|
|
</para>
|
|
<para>
|
|
<literal>timestamp '2001-09-29 03:00' - timestamp '2001-07-27 12:00'</literal>
|
|
<returnvalue>63 days 15:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>interval</type> <literal>*</literal> <type>double precision</type>
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Multiply an interval by a scalar
|
|
</para>
|
|
<para>
|
|
<literal>interval '1 second' * 900</literal>
|
|
<returnvalue>00:15:00</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>interval '1 day' * 21</literal>
|
|
<returnvalue>21 days</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>interval '1 hour' * 3.5</literal>
|
|
<returnvalue>03:30:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>interval</type> <literal>/</literal> <type>double precision</type>
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Divide an interval by a scalar
|
|
</para>
|
|
<para>
|
|
<literal>interval '1 hour' / 1.5</literal>
|
|
<returnvalue>00:40:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-datetime-table">
|
|
<title>Date/Time Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>age</primary>
|
|
</indexterm>
|
|
<function>age</function> ( <type>timestamp</type>, <type>timestamp</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract arguments, producing a <quote>symbolic</quote> result that
|
|
uses years and months, rather than just days
|
|
</para>
|
|
<para>
|
|
<literal>age(timestamp '2001-04-10', timestamp '1957-06-13')</literal>
|
|
<returnvalue>43 years 9 mons 27 days</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>age</function> ( <type>timestamp</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract argument from <function>current_date</function> (at midnight)
|
|
</para>
|
|
<para>
|
|
<literal>age(timestamp '1957-06-13')</literal>
|
|
<returnvalue>62 years 6 mons 10 days</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>clock_timestamp</primary>
|
|
</indexterm>
|
|
<function>clock_timestamp</function> ( )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date and time (changes during statement execution);
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>clock_timestamp()</literal>
|
|
<returnvalue>2019-12-23 14:39:53.662522-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_date</primary>
|
|
</indexterm>
|
|
<function>current_date</function>
|
|
<returnvalue>date</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date; see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>current_date</literal>
|
|
<returnvalue>2019-12-23</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_time</primary>
|
|
</indexterm>
|
|
<function>current_time</function>
|
|
<returnvalue>time with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current time of day; see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>current_time</literal>
|
|
<returnvalue>14:39:53.662522-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>current_time</function> ( <type>integer</type> )
|
|
<returnvalue>time with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current time of day, with limited precision;
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>current_time(2)</literal>
|
|
<returnvalue>14:39:53.66-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_timestamp</primary>
|
|
</indexterm>
|
|
<function>current_timestamp</function>
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date and time (start of current transaction);
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>current_timestamp</literal>
|
|
<returnvalue>2019-12-23 14:39:53.662522-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>current_timestamp</function> ( <type>integer</type> )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date and time (start of current transaction), with limited precision;
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>current_timestamp(0)</literal>
|
|
<returnvalue>2019-12-23 14:39:53-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>date_add</primary>
|
|
</indexterm>
|
|
<function>date_add</function> ( <type>timestamp with time zone</type>, <type>interval</type> <optional>, <type>text</type> </optional> )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Add an <type>interval</type> to a <type>timestamp with time
|
|
zone</type>, computing times of day and daylight-savings adjustments
|
|
according to the time zone named by the third argument, or the
|
|
current <xref linkend="guc-timezone"/> setting if that is omitted.
|
|
The form with two arguments is equivalent to the <type>timestamp with
|
|
time zone</type> <literal>+</literal> <type>interval</type> operator.
|
|
</para>
|
|
<para>
|
|
<literal>date_add('2021-10-31 00:00:00+02'::timestamptz, '1 day'::interval, 'Europe/Warsaw')</literal>
|
|
<returnvalue>2021-10-31 23:00:00+00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>date_bin</function> ( <type>interval</type>, <type>timestamp</type>, <type>timestamp</type> )
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Bin input into specified interval aligned with specified origin; see <xref linkend="functions-datetime-bin"/>
|
|
</para>
|
|
<para>
|
|
<literal>date_bin('15 minutes', timestamp '2001-02-16 20:38:40', timestamp '2001-02-16 20:05:00')</literal>
|
|
<returnvalue>2001-02-16 20:35:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>date_part</primary>
|
|
</indexterm>
|
|
<function>date_part</function> ( <type>text</type>, <type>timestamp</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Get timestamp subfield (equivalent to <function>extract</function>);
|
|
see <xref linkend="functions-datetime-extract"/>
|
|
</para>
|
|
<para>
|
|
<literal>date_part('hour', timestamp '2001-02-16 20:38:40')</literal>
|
|
<returnvalue>20</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>date_part</function> ( <type>text</type>, <type>interval</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Get interval subfield (equivalent to <function>extract</function>);
|
|
see <xref linkend="functions-datetime-extract"/>
|
|
</para>
|
|
<para>
|
|
<literal>date_part('month', interval '2 years 3 months')</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>date_subtract</primary>
|
|
</indexterm>
|
|
<function>date_subtract</function> ( <type>timestamp with time zone</type>, <type>interval</type> <optional>, <type>text</type> </optional> )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtract an <type>interval</type> from a <type>timestamp with time
|
|
zone</type>, computing times of day and daylight-savings adjustments
|
|
according to the time zone named by the third argument, or the
|
|
current <xref linkend="guc-timezone"/> setting if that is omitted.
|
|
The form with two arguments is equivalent to the <type>timestamp with
|
|
time zone</type> <literal>-</literal> <type>interval</type> operator.
|
|
</para>
|
|
<para>
|
|
<literal>date_subtract('2021-11-01 00:00:00+01'::timestamptz, '1 day'::interval, 'Europe/Warsaw')</literal>
|
|
<returnvalue>2021-10-30 22:00:00+00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>date_trunc</primary>
|
|
</indexterm>
|
|
<function>date_trunc</function> ( <type>text</type>, <type>timestamp</type> )
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Truncate to specified precision; see <xref linkend="functions-datetime-trunc"/>
|
|
</para>
|
|
<para>
|
|
<literal>date_trunc('hour', timestamp '2001-02-16 20:38:40')</literal>
|
|
<returnvalue>2001-02-16 20:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>date_trunc</function> ( <type>text</type>, <type>timestamp with time zone</type>, <type>text</type> )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Truncate to specified precision in the specified time zone; see
|
|
<xref linkend="functions-datetime-trunc"/>
|
|
</para>
|
|
<para>
|
|
<literal>date_trunc('day', timestamptz '2001-02-16 20:38:40+00', 'Australia/Sydney')</literal>
|
|
<returnvalue>2001-02-16 13:00:00+00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>date_trunc</function> ( <type>text</type>, <type>interval</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Truncate to specified precision; see
|
|
<xref linkend="functions-datetime-trunc"/>
|
|
</para>
|
|
<para>
|
|
<literal>date_trunc('hour', interval '2 days 3 hours 40 minutes')</literal>
|
|
<returnvalue>2 days 03:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>extract</primary>
|
|
</indexterm>
|
|
<function>extract</function> ( <parameter>field</parameter> <literal>from</literal> <type>timestamp</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Get timestamp subfield; see <xref linkend="functions-datetime-extract"/>
|
|
</para>
|
|
<para>
|
|
<literal>extract(hour from timestamp '2001-02-16 20:38:40')</literal>
|
|
<returnvalue>20</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>extract</function> ( <parameter>field</parameter> <literal>from</literal> <type>interval</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Get interval subfield; see <xref linkend="functions-datetime-extract"/>
|
|
</para>
|
|
<para>
|
|
<literal>extract(month from interval '2 years 3 months')</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>isfinite</primary>
|
|
</indexterm>
|
|
<function>isfinite</function> ( <type>date</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test for finite date (not +/-infinity)
|
|
</para>
|
|
<para>
|
|
<literal>isfinite(date '2001-02-16')</literal>
|
|
<returnvalue>true</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>isfinite</function> ( <type>timestamp</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test for finite timestamp (not +/-infinity)
|
|
</para>
|
|
<para>
|
|
<literal>isfinite(timestamp 'infinity')</literal>
|
|
<returnvalue>false</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>isfinite</function> ( <type>interval</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Test for finite interval (not +/-infinity)
|
|
</para>
|
|
<para>
|
|
<literal>isfinite(interval '4 hours')</literal>
|
|
<returnvalue>true</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm id="function-justify-days">
|
|
<primary>justify_days</primary>
|
|
</indexterm>
|
|
<function>justify_days</function> ( <type>interval</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Adjust interval, converting 30-day time periods to months
|
|
</para>
|
|
<para>
|
|
<literal>justify_days(interval '1 year 65 days')</literal>
|
|
<returnvalue>1 year 2 mons 5 days</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm id="function-justify-hours">
|
|
<primary>justify_hours</primary>
|
|
</indexterm>
|
|
<function>justify_hours</function> ( <type>interval</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Adjust interval, converting 24-hour time periods to days
|
|
</para>
|
|
<para>
|
|
<literal>justify_hours(interval '50 hours 10 minutes')</literal>
|
|
<returnvalue>2 days 02:10:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>justify_interval</primary>
|
|
</indexterm>
|
|
<function>justify_interval</function> ( <type>interval</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Adjust interval using <function>justify_days</function>
|
|
and <function>justify_hours</function>, with additional sign
|
|
adjustments
|
|
</para>
|
|
<para>
|
|
<literal>justify_interval(interval '1 mon -1 hour')</literal>
|
|
<returnvalue>29 days 23:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>localtime</primary>
|
|
</indexterm>
|
|
<function>localtime</function>
|
|
<returnvalue>time</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current time of day;
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>localtime</literal>
|
|
<returnvalue>14:39:53.662522</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>localtime</function> ( <type>integer</type> )
|
|
<returnvalue>time</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current time of day, with limited precision;
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>localtime(0)</literal>
|
|
<returnvalue>14:39:53</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>localtimestamp</primary>
|
|
</indexterm>
|
|
<function>localtimestamp</function>
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date and time (start of current transaction);
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>localtimestamp</literal>
|
|
<returnvalue>2019-12-23 14:39:53.662522</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>localtimestamp</function> ( <type>integer</type> )
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date and time (start of current
|
|
transaction), with limited precision;
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>localtimestamp(2)</literal>
|
|
<returnvalue>2019-12-23 14:39:53.66</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>make_date</primary>
|
|
</indexterm>
|
|
<function>make_date</function> ( <parameter>year</parameter> <type>int</type>,
|
|
<parameter>month</parameter> <type>int</type>,
|
|
<parameter>day</parameter> <type>int</type> )
|
|
<returnvalue>date</returnvalue>
|
|
</para>
|
|
<para>
|
|
Create date from year, month and day fields
|
|
(negative years signify BC)
|
|
</para>
|
|
<para>
|
|
<literal>make_date(2013, 7, 15)</literal>
|
|
<returnvalue>2013-07-15</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature"><indexterm>
|
|
<primary>make_interval</primary>
|
|
</indexterm>
|
|
<function>make_interval</function> ( <optional> <parameter>years</parameter> <type>int</type>
|
|
<optional>, <parameter>months</parameter> <type>int</type>
|
|
<optional>, <parameter>weeks</parameter> <type>int</type>
|
|
<optional>, <parameter>days</parameter> <type>int</type>
|
|
<optional>, <parameter>hours</parameter> <type>int</type>
|
|
<optional>, <parameter>mins</parameter> <type>int</type>
|
|
<optional>, <parameter>secs</parameter> <type>double precision</type>
|
|
</optional></optional></optional></optional></optional></optional></optional> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Create interval from years, months, weeks, days, hours, minutes and
|
|
seconds fields, each of which can default to zero
|
|
</para>
|
|
<para>
|
|
<literal>make_interval(days => 10)</literal>
|
|
<returnvalue>10 days</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>make_time</primary>
|
|
</indexterm>
|
|
<function>make_time</function> ( <parameter>hour</parameter> <type>int</type>,
|
|
<parameter>min</parameter> <type>int</type>,
|
|
<parameter>sec</parameter> <type>double precision</type> )
|
|
<returnvalue>time</returnvalue>
|
|
</para>
|
|
<para>
|
|
Create time from hour, minute and seconds fields
|
|
</para>
|
|
<para>
|
|
<literal>make_time(8, 15, 23.5)</literal>
|
|
<returnvalue>08:15:23.5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>make_timestamp</primary>
|
|
</indexterm>
|
|
<function>make_timestamp</function> ( <parameter>year</parameter> <type>int</type>,
|
|
<parameter>month</parameter> <type>int</type>,
|
|
<parameter>day</parameter> <type>int</type>,
|
|
<parameter>hour</parameter> <type>int</type>,
|
|
<parameter>min</parameter> <type>int</type>,
|
|
<parameter>sec</parameter> <type>double precision</type> )
|
|
<returnvalue>timestamp</returnvalue>
|
|
</para>
|
|
<para>
|
|
Create timestamp from year, month, day, hour, minute and seconds fields
|
|
(negative years signify BC)
|
|
</para>
|
|
<para>
|
|
<literal>make_timestamp(2013, 7, 15, 8, 15, 23.5)</literal>
|
|
<returnvalue>2013-07-15 08:15:23.5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>make_timestamptz</primary>
|
|
</indexterm>
|
|
<function>make_timestamptz</function> ( <parameter>year</parameter> <type>int</type>,
|
|
<parameter>month</parameter> <type>int</type>,
|
|
<parameter>day</parameter> <type>int</type>,
|
|
<parameter>hour</parameter> <type>int</type>,
|
|
<parameter>min</parameter> <type>int</type>,
|
|
<parameter>sec</parameter> <type>double precision</type>
|
|
<optional>, <parameter>timezone</parameter> <type>text</type> </optional> )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Create timestamp with time zone from year, month, day, hour, minute
|
|
and seconds fields (negative years signify BC).
|
|
If <parameter>timezone</parameter> is not
|
|
specified, the current time zone is used; the examples assume the
|
|
session time zone is <literal>Europe/London</literal>
|
|
</para>
|
|
<para>
|
|
<literal>make_timestamptz(2013, 7, 15, 8, 15, 23.5)</literal>
|
|
<returnvalue>2013-07-15 08:15:23.5+01</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>make_timestamptz(2013, 7, 15, 8, 15, 23.5, 'America/New_York')</literal>
|
|
<returnvalue>2013-07-15 13:15:23.5+01</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>now</primary>
|
|
</indexterm>
|
|
<function>now</function> ( )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date and time (start of current transaction);
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>now()</literal>
|
|
<returnvalue>2019-12-23 14:39:53.662522-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>statement_timestamp</primary>
|
|
</indexterm>
|
|
<function>statement_timestamp</function> ( )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date and time (start of current statement);
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>statement_timestamp()</literal>
|
|
<returnvalue>2019-12-23 14:39:53.662522-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>timeofday</primary>
|
|
</indexterm>
|
|
<function>timeofday</function> ( )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date and time
|
|
(like <function>clock_timestamp</function>, but as a <type>text</type> string);
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>timeofday()</literal>
|
|
<returnvalue>Mon Dec 23 14:39:53.662522 2019 EST</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>transaction_timestamp</primary>
|
|
</indexterm>
|
|
<function>transaction_timestamp</function> ( )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Current date and time (start of current transaction);
|
|
see <xref linkend="functions-datetime-current"/>
|
|
</para>
|
|
<para>
|
|
<literal>transaction_timestamp()</literal>
|
|
<returnvalue>2019-12-23 14:39:53.662522-05</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_timestamp</primary>
|
|
</indexterm>
|
|
<function>to_timestamp</function> ( <type>double precision</type> )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Convert Unix epoch (seconds since 1970-01-01 00:00:00+00) to
|
|
timestamp with time zone
|
|
</para>
|
|
<para>
|
|
<literal>to_timestamp(1284352323)</literal>
|
|
<returnvalue>2010-09-13 04:32:03+00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<indexterm>
|
|
<primary>OVERLAPS</primary>
|
|
</indexterm>
|
|
In addition to these functions, the SQL <literal>OVERLAPS</literal> operator is
|
|
supported:
|
|
<synopsis>
|
|
(<replaceable>start1</replaceable>, <replaceable>end1</replaceable>) OVERLAPS (<replaceable>start2</replaceable>, <replaceable>end2</replaceable>)
|
|
(<replaceable>start1</replaceable>, <replaceable>length1</replaceable>) OVERLAPS (<replaceable>start2</replaceable>, <replaceable>length2</replaceable>)
|
|
</synopsis>
|
|
This expression yields true when two time periods (defined by their
|
|
endpoints) overlap, false when they do not overlap. The endpoints
|
|
can be specified as pairs of dates, times, or time stamps; or as
|
|
a date, time, or time stamp followed by an interval. When a pair
|
|
of values is provided, either the start or the end can be written
|
|
first; <literal>OVERLAPS</literal> automatically takes the earlier value
|
|
of the pair as the start. Each time period is considered to
|
|
represent the half-open interval <replaceable>start</replaceable> <literal><=</literal>
|
|
<replaceable>time</replaceable> <literal><</literal> <replaceable>end</replaceable>, unless
|
|
<replaceable>start</replaceable> and <replaceable>end</replaceable> are equal in which case it
|
|
represents that single time instant. This means for instance that two
|
|
time periods with only an endpoint in common do not overlap.
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS
|
|
(DATE '2001-10-30', DATE '2002-10-30');
|
|
<lineannotation>Result: </lineannotation><computeroutput>true</computeroutput>
|
|
SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS
|
|
(DATE '2001-10-30', DATE '2002-10-30');
|
|
<lineannotation>Result: </lineannotation><computeroutput>false</computeroutput>
|
|
SELECT (DATE '2001-10-29', DATE '2001-10-30') OVERLAPS
|
|
(DATE '2001-10-30', DATE '2001-10-31');
|
|
<lineannotation>Result: </lineannotation><computeroutput>false</computeroutput>
|
|
SELECT (DATE '2001-10-30', DATE '2001-10-30') OVERLAPS
|
|
(DATE '2001-10-30', DATE '2001-10-31');
|
|
<lineannotation>Result: </lineannotation><computeroutput>true</computeroutput>
|
|
</screen>
|
|
|
|
<para>
|
|
When adding an <type>interval</type> value to (or subtracting an
|
|
<type>interval</type> value from) a <type>timestamp</type>
|
|
or <type>timestamp with time zone</type> value, the months, days, and
|
|
microseconds fields of the <type>interval</type> value are handled in turn.
|
|
First, a nonzero months field advances or decrements the date of the
|
|
timestamp by the indicated number of months, keeping the day of month the
|
|
same unless it would be past the end of the new month, in which case the
|
|
last day of that month is used. (For example, March 31 plus 1 month
|
|
becomes April 30, but March 31 plus 2 months becomes May 31.)
|
|
Then the days field advances or decrements the date of the timestamp by
|
|
the indicated number of days. In both these steps the local time of day
|
|
is kept the same. Finally, if there is a nonzero microseconds field, it
|
|
is added or subtracted literally.
|
|
When doing arithmetic on a <type>timestamp with time zone</type> value in
|
|
a time zone that recognizes DST, this means that adding or subtracting
|
|
(say) <literal>interval '1 day'</literal> does not necessarily have the
|
|
same result as adding or subtracting <literal>interval '24
|
|
hours'</literal>.
|
|
For example, with the session time zone set
|
|
to <literal>America/Denver</literal>:
|
|
<screen>
|
|
SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '1 day';
|
|
<lineannotation>Result: </lineannotation><computeroutput>2005-04-03 12:00:00-06</computeroutput>
|
|
SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '24 hours';
|
|
<lineannotation>Result: </lineannotation><computeroutput>2005-04-03 13:00:00-06</computeroutput>
|
|
</screen>
|
|
This happens because an hour was skipped due to a change in daylight saving
|
|
time at <literal>2005-04-03 02:00:00</literal> in time zone
|
|
<literal>America/Denver</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
Note there can be ambiguity in the <literal>months</literal> field returned by
|
|
<function>age</function> because different months have different numbers of
|
|
days. <productname>PostgreSQL</productname>'s approach uses the month from the
|
|
earlier of the two dates when calculating partial months. For example,
|
|
<literal>age('2004-06-01', '2004-04-30')</literal> uses April to yield
|
|
<literal>1 mon 1 day</literal>, while using May would yield <literal>1 mon 2
|
|
days</literal> because May has 31 days, while April has only 30.
|
|
</para>
|
|
|
|
<para>
|
|
Subtraction of dates and timestamps can also be complex. One conceptually
|
|
simple way to perform subtraction is to convert each value to a number
|
|
of seconds using <literal>EXTRACT(EPOCH FROM ...)</literal>, then subtract the
|
|
results; this produces the
|
|
number of <emphasis>seconds</emphasis> between the two values. This will adjust
|
|
for the number of days in each month, timezone changes, and daylight
|
|
saving time adjustments. Subtraction of date or timestamp
|
|
values with the <quote><literal>-</literal></quote> operator
|
|
returns the number of days (24-hours) and hours/minutes/seconds
|
|
between the values, making the same adjustments. The <function>age</function>
|
|
function returns years, months, days, and hours/minutes/seconds,
|
|
performing field-by-field subtraction and then adjusting for negative
|
|
field values. The following queries illustrate the differences in these
|
|
approaches. The sample results were produced with <literal>timezone
|
|
= 'US/Eastern'</literal>; there is a daylight saving time change between the
|
|
two dates used:
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') -
|
|
EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00');
|
|
<lineannotation>Result: </lineannotation><computeroutput>10537200.000000</computeroutput>
|
|
SELECT (EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') -
|
|
EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00'))
|
|
/ 60 / 60 / 24;
|
|
<lineannotation>Result: </lineannotation><computeroutput>121.9583333333333333</computeroutput>
|
|
SELECT timestamptz '2013-07-01 12:00:00' - timestamptz '2013-03-01 12:00:00';
|
|
<lineannotation>Result: </lineannotation><computeroutput>121 days 23:00:00</computeroutput>
|
|
SELECT age(timestamptz '2013-07-01 12:00:00', timestamptz '2013-03-01 12:00:00');
|
|
<lineannotation>Result: </lineannotation><computeroutput>4 mons</computeroutput>
|
|
</screen>
|
|
|
|
<sect2 id="functions-datetime-extract">
|
|
<title><function>EXTRACT</function>, <function>date_part</function></title>
|
|
|
|
<indexterm>
|
|
<primary>date_part</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>extract</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
EXTRACT(<replaceable>field</replaceable> FROM <replaceable>source</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>extract</function> function retrieves subfields
|
|
such as year or hour from date/time values.
|
|
<replaceable>source</replaceable> must be a value expression of
|
|
type <type>timestamp</type>, <type>date</type>, <type>time</type>,
|
|
or <type>interval</type>. (Timestamps and times can be with or
|
|
without time zone.)
|
|
<replaceable>field</replaceable> is an identifier or
|
|
string that selects what field to extract from the source value.
|
|
Not all fields are valid for every input data type; for example, fields
|
|
smaller than a day cannot be extracted from a <type>date</type>, while
|
|
fields of a day or more cannot be extracted from a <type>time</type>.
|
|
The <function>extract</function> function returns values of type
|
|
<type>numeric</type>.
|
|
</para>
|
|
|
|
<para>
|
|
The following are valid field names:
|
|
|
|
<!-- alphabetical -->
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><literal>century</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The century; for <type>interval</type> values, the year field
|
|
divided by 100
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(CENTURY FROM TIMESTAMP '2000-12-16 12:21:13');
|
|
<lineannotation>Result: </lineannotation><computeroutput>20</computeroutput>
|
|
SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>21</computeroutput>
|
|
SELECT EXTRACT(CENTURY FROM DATE '0001-01-01 AD');
|
|
<lineannotation>Result: </lineannotation><computeroutput>1</computeroutput>
|
|
SELECT EXTRACT(CENTURY FROM DATE '0001-12-31 BC');
|
|
<lineannotation>Result: </lineannotation><computeroutput>-1</computeroutput>
|
|
SELECT EXTRACT(CENTURY FROM INTERVAL '2001 years');
|
|
<lineannotation>Result: </lineannotation><computeroutput>20</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>day</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The day of the month (1–31); for <type>interval</type>
|
|
values, the number of days
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(DAY FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>16</computeroutput>
|
|
SELECT EXTRACT(DAY FROM INTERVAL '40 days 1 minute');
|
|
<lineannotation>Result: </lineannotation><computeroutput>40</computeroutput>
|
|
</screen>
|
|
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>decade</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The year field divided by 10
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(DECADE FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>200</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>dow</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The day of the week as Sunday (<literal>0</literal>) to
|
|
Saturday (<literal>6</literal>)
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>5</computeroutput>
|
|
</screen>
|
|
<para>
|
|
Note that <function>extract</function>'s day of the week numbering
|
|
differs from that of the <function>to_char(...,
|
|
'D')</function> function.
|
|
</para>
|
|
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>doy</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The day of the year (1–365/366)
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>47</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>epoch</literal></term>
|
|
<listitem>
|
|
<para>
|
|
For <type>timestamp with time zone</type> values, the
|
|
number of seconds since 1970-01-01 00:00:00 UTC (negative for
|
|
timestamps before that);
|
|
for <type>date</type> and <type>timestamp</type> values, the
|
|
nominal number of seconds since 1970-01-01 00:00:00,
|
|
without regard to timezone or daylight-savings rules;
|
|
for <type>interval</type> values, the total number
|
|
of seconds in the interval
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40.12-08');
|
|
<lineannotation>Result: </lineannotation><computeroutput>982384720.120000</computeroutput>
|
|
SELECT EXTRACT(EPOCH FROM TIMESTAMP '2001-02-16 20:38:40.12');
|
|
<lineannotation>Result: </lineannotation><computeroutput>982355920.120000</computeroutput>
|
|
SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours');
|
|
<lineannotation>Result: </lineannotation><computeroutput>442800.000000</computeroutput>
|
|
</screen>
|
|
|
|
<para>
|
|
You can convert an epoch value back to a <type>timestamp with time zone</type>
|
|
with <function>to_timestamp</function>:
|
|
</para>
|
|
<screen>
|
|
SELECT to_timestamp(982384720.12);
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001-02-17 04:38:40.12+00</computeroutput>
|
|
</screen>
|
|
|
|
<para>
|
|
Beware that applying <function>to_timestamp</function> to an epoch
|
|
extracted from a <type>date</type> or <type>timestamp</type> value
|
|
could produce a misleading result: the result will effectively
|
|
assume that the original value had been given in UTC, which might
|
|
not be the case.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>hour</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The hour field (0–23 in timestamps, unrestricted in
|
|
intervals)
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>20</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>isodow</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The day of the week as Monday (<literal>1</literal>) to
|
|
Sunday (<literal>7</literal>)
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(ISODOW FROM TIMESTAMP '2001-02-18 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>7</computeroutput>
|
|
</screen>
|
|
<para>
|
|
This is identical to <literal>dow</literal> except for Sunday. This
|
|
matches the <acronym>ISO</acronym> 8601 day of the week numbering.
|
|
</para>
|
|
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>isoyear</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The <acronym>ISO</acronym> 8601 week-numbering year that the date
|
|
falls in
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-01');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2005</computeroutput>
|
|
SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-02');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2006</computeroutput>
|
|
</screen>
|
|
|
|
<para>
|
|
Each <acronym>ISO</acronym> 8601 week-numbering year begins with the
|
|
Monday of the week containing the 4th of January, so in early
|
|
January or late December the <acronym>ISO</acronym> year may be
|
|
different from the Gregorian year. See the <literal>week</literal>
|
|
field for more information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>julian</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The <firstterm>Julian Date</firstterm> corresponding to the
|
|
date or timestamp. Timestamps
|
|
that are not local midnight result in a fractional value. See
|
|
<xref linkend="datetime-julian-dates"/> for more information.
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(JULIAN FROM DATE '2006-01-01');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2453737</computeroutput>
|
|
SELECT EXTRACT(JULIAN FROM TIMESTAMP '2006-01-01 12:00');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2453737.50000000000000000000</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>microseconds</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The seconds field, including fractional parts, multiplied by 1
|
|
000 000; note that this includes full seconds
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(MICROSECONDS FROM TIME '17:12:28.5');
|
|
<lineannotation>Result: </lineannotation><computeroutput>28500000</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>millennium</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The millennium; for <type>interval</type> values, the year field
|
|
divided by 1000
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(MILLENNIUM FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>3</computeroutput>
|
|
SELECT EXTRACT(MILLENNIUM FROM INTERVAL '2001 years');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2</computeroutput>
|
|
</screen>
|
|
|
|
<para>
|
|
Years in the 1900s are in the second millennium.
|
|
The third millennium started January 1, 2001.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>milliseconds</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The seconds field, including fractional parts, multiplied by
|
|
1000. Note that this includes full seconds.
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(MILLISECONDS FROM TIME '17:12:28.5');
|
|
<lineannotation>Result: </lineannotation><computeroutput>28500.000</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>minute</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The minutes field (0–59)
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(MINUTE FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>38</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>month</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The number of the month within the year (1–12);
|
|
for <type>interval</type> values, the number of months modulo 12
|
|
(0–11)
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(MONTH FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2</computeroutput>
|
|
SELECT EXTRACT(MONTH FROM INTERVAL '2 years 3 months');
|
|
<lineannotation>Result: </lineannotation><computeroutput>3</computeroutput>
|
|
SELECT EXTRACT(MONTH FROM INTERVAL '2 years 13 months');
|
|
<lineannotation>Result: </lineannotation><computeroutput>1</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>quarter</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The quarter of the year (1–4) that the date is in
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>1</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>second</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The seconds field, including any fractional seconds
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(SECOND FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>40.000000</computeroutput>
|
|
SELECT EXTRACT(SECOND FROM TIME '17:12:28.5');
|
|
<lineannotation>Result: </lineannotation><computeroutput>28.500000</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><literal>timezone</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The time zone offset from UTC, measured in seconds. Positive values
|
|
correspond to time zones east of UTC, negative values to
|
|
zones west of UTC. (Technically,
|
|
<productname>PostgreSQL</productname> does not use UTC because
|
|
leap seconds are not handled.)
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>timezone_hour</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The hour component of the time zone offset
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>timezone_minute</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The minute component of the time zone offset
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>week</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The number of the <acronym>ISO</acronym> 8601 week-numbering week of
|
|
the year. By definition, ISO weeks start on Mondays and the first
|
|
week of a year contains January 4 of that year. In other words, the
|
|
first Thursday of a year is in week 1 of that year.
|
|
</para>
|
|
<para>
|
|
In the ISO week-numbering system, it is possible for early-January
|
|
dates to be part of the 52nd or 53rd week of the previous year, and for
|
|
late-December dates to be part of the first week of the next year.
|
|
For example, <literal>2005-01-01</literal> is part of the 53rd week of year
|
|
2004, and <literal>2006-01-01</literal> is part of the 52nd week of year
|
|
2005, while <literal>2012-12-31</literal> is part of the first week of 2013.
|
|
It's recommended to use the <literal>isoyear</literal> field together with
|
|
<literal>week</literal> to get consistent results.
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(WEEK FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>7</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>year</literal></term>
|
|
<listitem>
|
|
<para>
|
|
The year field. Keep in mind there is no <literal>0 AD</literal>, so subtracting
|
|
<literal>BC</literal> years from <literal>AD</literal> years should be done with care.
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT EXTRACT(YEAR FROM TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001</computeroutput>
|
|
</screen>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</para>
|
|
|
|
<para>
|
|
When processing an <type>interval</type> value,
|
|
the <function>extract</function> function produces field values that
|
|
match the interpretation used by the interval output function. This
|
|
can produce surprising results if one starts with a non-normalized
|
|
interval representation, for example:
|
|
<screen>
|
|
SELECT INTERVAL '80 minutes';
|
|
<lineannotation>Result: </lineannotation><computeroutput>01:20:00</computeroutput>
|
|
SELECT EXTRACT(MINUTES FROM INTERVAL '80 minutes');
|
|
<lineannotation>Result: </lineannotation><computeroutput>20</computeroutput>
|
|
</screen>
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
When the input value is +/-Infinity, <function>extract</function> returns
|
|
+/-Infinity for monotonically-increasing fields (<literal>epoch</literal>,
|
|
<literal>julian</literal>, <literal>year</literal>, <literal>isoyear</literal>,
|
|
<literal>decade</literal>, <literal>century</literal>, and <literal>millennium</literal>
|
|
for <type>timestamp</type> inputs; <literal>epoch</literal>, <literal>hour</literal>,
|
|
<literal>day</literal>, <literal>year</literal>, <literal>decade</literal>,
|
|
<literal>century</literal>, and <literal>millennium</literal> for
|
|
<type>interval</type> inputs).
|
|
For other fields, NULL is returned. <productname>PostgreSQL</productname>
|
|
versions before 9.6 returned zero for all cases of infinite input.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
The <function>extract</function> function is primarily intended
|
|
for computational processing. For formatting date/time values for
|
|
display, see <xref linkend="functions-formatting"/>.
|
|
</para>
|
|
|
|
<para>
|
|
The <function>date_part</function> function is modeled on the traditional
|
|
<productname>Ingres</productname> equivalent to the
|
|
<acronym>SQL</acronym>-standard function <function>extract</function>:
|
|
<synopsis>
|
|
date_part('<replaceable>field</replaceable>', <replaceable>source</replaceable>)
|
|
</synopsis>
|
|
Note that here the <replaceable>field</replaceable> parameter needs to
|
|
be a string value, not a name. The valid field names for
|
|
<function>date_part</function> are the same as for
|
|
<function>extract</function>.
|
|
For historical reasons, the <function>date_part</function> function
|
|
returns values of type <type>double precision</type>. This can result in
|
|
a loss of precision in certain uses. Using <function>extract</function>
|
|
is recommended instead.
|
|
</para>
|
|
|
|
<screen>
|
|
SELECT date_part('day', TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>16</computeroutput>
|
|
SELECT date_part('hour', INTERVAL '4 hours 3 minutes');
|
|
<lineannotation>Result: </lineannotation><computeroutput>4</computeroutput>
|
|
</screen>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-datetime-trunc">
|
|
<title><function>date_trunc</function></title>
|
|
|
|
<indexterm>
|
|
<primary>date_trunc</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The function <function>date_trunc</function> is conceptually
|
|
similar to the <function>trunc</function> function for numbers.
|
|
</para>
|
|
|
|
<para>
|
|
<synopsis>
|
|
date_trunc(<replaceable>field</replaceable>, <replaceable>source</replaceable> [, <replaceable>time_zone</replaceable> ])
|
|
</synopsis>
|
|
<replaceable>source</replaceable> is a value expression of type
|
|
<type>timestamp</type>, <type>timestamp with time zone</type>,
|
|
or <type>interval</type>.
|
|
(Values of type <type>date</type> and
|
|
<type>time</type> are cast automatically to <type>timestamp</type> or
|
|
<type>interval</type>, respectively.)
|
|
<replaceable>field</replaceable> selects to which precision to
|
|
truncate the input value. The return value is likewise of type
|
|
<type>timestamp</type>, <type>timestamp with time zone</type>,
|
|
or <type>interval</type>,
|
|
and it has all fields that are less significant than the
|
|
selected one set to zero (or one, for day and month).
|
|
</para>
|
|
|
|
<para>
|
|
Valid values for <replaceable>field</replaceable> are:
|
|
<simplelist>
|
|
<member><literal>microseconds</literal></member>
|
|
<member><literal>milliseconds</literal></member>
|
|
<member><literal>second</literal></member>
|
|
<member><literal>minute</literal></member>
|
|
<member><literal>hour</literal></member>
|
|
<member><literal>day</literal></member>
|
|
<member><literal>week</literal></member>
|
|
<member><literal>month</literal></member>
|
|
<member><literal>quarter</literal></member>
|
|
<member><literal>year</literal></member>
|
|
<member><literal>decade</literal></member>
|
|
<member><literal>century</literal></member>
|
|
<member><literal>millennium</literal></member>
|
|
</simplelist>
|
|
</para>
|
|
|
|
<para>
|
|
When the input value is of type <type>timestamp with time zone</type>,
|
|
the truncation is performed with respect to a particular time zone;
|
|
for example, truncation to <literal>day</literal> produces a value that
|
|
is midnight in that zone. By default, truncation is done with respect
|
|
to the current <xref linkend="guc-timezone"/> setting, but the
|
|
optional <replaceable>time_zone</replaceable> argument can be provided
|
|
to specify a different time zone. The time zone name can be specified
|
|
in any of the ways described in <xref linkend="datatype-timezones"/>.
|
|
</para>
|
|
|
|
<para>
|
|
A time zone cannot be specified when processing <type>timestamp without
|
|
time zone</type> or <type>interval</type> inputs. These are always
|
|
taken at face value.
|
|
</para>
|
|
|
|
<para>
|
|
Examples (assuming the local time zone is <literal>America/New_York</literal>):
|
|
<screen>
|
|
SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 20:00:00</computeroutput>
|
|
SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001-01-01 00:00:00</computeroutput>
|
|
SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 00:00:00-05</computeroutput>
|
|
SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00', 'Australia/Sydney');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 08:00:00-05</computeroutput>
|
|
SELECT date_trunc('hour', INTERVAL '3 days 02:47:33');
|
|
<lineannotation>Result: </lineannotation><computeroutput>3 days 02:00:00</computeroutput>
|
|
</screen>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-datetime-bin">
|
|
<title><function>date_bin</function></title>
|
|
|
|
<indexterm>
|
|
<primary>date_bin</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The function <function>date_bin</function> <quote>bins</quote> the input
|
|
timestamp into the specified interval (the <firstterm>stride</firstterm>)
|
|
aligned with a specified origin.
|
|
</para>
|
|
|
|
<para>
|
|
<synopsis>
|
|
date_bin(<replaceable>stride</replaceable>, <replaceable>source</replaceable>, <replaceable>origin</replaceable>)
|
|
</synopsis>
|
|
<replaceable>source</replaceable> is a value expression of type
|
|
<type>timestamp</type> or <type>timestamp with time zone</type>. (Values
|
|
of type <type>date</type> are cast automatically to
|
|
<type>timestamp</type>.) <replaceable>stride</replaceable> is a value
|
|
expression of type <type>interval</type>. The return value is likewise
|
|
of type <type>timestamp</type> or <type>timestamp with time zone</type>,
|
|
and it marks the beginning of the bin into which the
|
|
<replaceable>source</replaceable> is placed.
|
|
</para>
|
|
|
|
<para>
|
|
Examples:
|
|
<screen>
|
|
SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-01-01');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2020-02-11 15:30:00</computeroutput>
|
|
SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-01-01 00:02:30');
|
|
<lineannotation>Result: </lineannotation><computeroutput>2020-02-11 15:32:30</computeroutput>
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
In the case of full units (1 minute, 1 hour, etc.), it gives the same result as
|
|
the analogous <function>date_trunc</function> call, but the difference is
|
|
that <function>date_bin</function> can truncate to an arbitrary interval.
|
|
</para>
|
|
|
|
<para>
|
|
The <parameter>stride</parameter> interval must be greater than zero and
|
|
cannot contain units of month or larger.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-datetime-zoneconvert">
|
|
<title><literal>AT TIME ZONE and AT LOCAL</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>time zone</primary>
|
|
<secondary>conversion</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>AT TIME ZONE</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>AT LOCAL</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <literal>AT TIME ZONE</literal> operator converts time
|
|
stamp <emphasis>without</emphasis> time zone to/from
|
|
time stamp <emphasis>with</emphasis> time zone, and
|
|
<type>time with time zone</type> values to different time
|
|
zones. <xref linkend="functions-datetime-zoneconvert-table"/> shows its
|
|
variants.
|
|
</para>
|
|
|
|
<table id="functions-datetime-zoneconvert-table">
|
|
<title><literal>AT TIME ZONE</literal> and <literal>AT LOCAL</literal> Variants</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>timestamp without time zone</type> <literal>AT TIME ZONE</literal> <replaceable>zone</replaceable>
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts given time stamp <emphasis>without</emphasis> time zone to
|
|
time stamp <emphasis>with</emphasis> time zone, assuming the given
|
|
value is in the named time zone.
|
|
</para>
|
|
<para>
|
|
<literal>timestamp '2001-02-16 20:38:40' at time zone 'America/Denver'</literal>
|
|
<returnvalue>2001-02-17 03:38:40+00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>timestamp without time zone</type> <literal>AT LOCAL</literal>
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts given time stamp <emphasis>without</emphasis> time zone to
|
|
time stamp <emphasis>with</emphasis> the session's
|
|
<varname>TimeZone</varname> value as time zone.
|
|
</para>
|
|
<para>
|
|
<literal>timestamp '2001-02-16 20:38:40' at local</literal>
|
|
<returnvalue>2001-02-17 03:38:40+00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>timestamp with time zone</type> <literal>AT TIME ZONE</literal> <replaceable>zone</replaceable>
|
|
<returnvalue>timestamp without time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts given time stamp <emphasis>with</emphasis> time zone to
|
|
time stamp <emphasis>without</emphasis> time zone, as the time would
|
|
appear in that zone.
|
|
</para>
|
|
<para>
|
|
<literal>timestamp with time zone '2001-02-16 20:38:40-05' at time zone 'America/Denver'</literal>
|
|
<returnvalue>2001-02-16 18:38:40</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>timestamp with time zone</type> <literal>AT LOCAL</literal>
|
|
<returnvalue>timestamp without time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts given time stamp <emphasis>with</emphasis> time zone to
|
|
time stamp <emphasis>without</emphasis> time zone, as the time would
|
|
appear with the session's <varname>TimeZone</varname> value as time zone.
|
|
</para>
|
|
<para>
|
|
<literal>timestamp with time zone '2001-02-16 20:38:40-05' at local</literal>
|
|
<returnvalue>2001-02-16 18:38:40</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>time with time zone</type> <literal>AT TIME ZONE</literal> <replaceable>zone</replaceable>
|
|
<returnvalue>time with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts given time <emphasis>with</emphasis> time zone to a new time
|
|
zone. Since no date is supplied, this uses the currently active UTC
|
|
offset for the named destination zone.
|
|
</para>
|
|
<para>
|
|
<literal>time with time zone '05:34:17-05' at time zone 'UTC'</literal>
|
|
<returnvalue>10:34:17+00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>time with time zone</type> <literal>AT LOCAL</literal>
|
|
<returnvalue>time with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts given time <emphasis>with</emphasis> time zone to a new time
|
|
zone. Since no date is supplied, this uses the currently active UTC
|
|
offset for the session's <varname>TimeZone</varname> value.
|
|
</para>
|
|
<para>
|
|
Assuming the session's <varname>TimeZone</varname> is set to <literal>UTC</literal>:
|
|
</para>
|
|
<para>
|
|
<literal>time with time zone '05:34:17-05' at local</literal>
|
|
<returnvalue>10:34:17+00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
In these expressions, the desired time zone <replaceable>zone</replaceable> can be
|
|
specified either as a text value (e.g., <literal>'America/Los_Angeles'</literal>)
|
|
or as an interval (e.g., <literal>INTERVAL '-08:00'</literal>).
|
|
In the text case, a time zone name can be specified in any of the ways
|
|
described in <xref linkend="datatype-timezones"/>.
|
|
The interval case is only useful for zones that have fixed offsets from
|
|
UTC, so it is not very common in practice.
|
|
</para>
|
|
|
|
<para>
|
|
The syntax <literal>AT LOCAL</literal> may be used as shorthand for
|
|
<literal>AT TIME ZONE <replaceable>local</replaceable></literal>, where
|
|
<replaceable>local</replaceable> is the session's
|
|
<varname>TimeZone</varname> value.
|
|
</para>
|
|
|
|
<para>
|
|
Examples (assuming the current <xref linkend="guc-timezone"/> setting
|
|
is <literal>America/Los_Angeles</literal>):
|
|
<screen>
|
|
SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'America/Denver';
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 19:38:40-08</computeroutput>
|
|
SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'America/Denver';
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 18:38:40</computeroutput>
|
|
SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'Asia/Tokyo' AT TIME ZONE 'America/Chicago';
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 05:38:40</computeroutput>
|
|
SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT LOCAL;
|
|
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 17:38:40</computeroutput>
|
|
SELECT TIME WITH TIME ZONE '20:38:40-05' AT LOCAL;
|
|
<lineannotation>Result: </lineannotation><computeroutput>17:38:40</computeroutput>
|
|
</screen>
|
|
The first example adds a time zone to a value that lacks it, and
|
|
displays the value using the current <varname>TimeZone</varname>
|
|
setting. The second example shifts the time stamp with time zone value
|
|
to the specified time zone, and returns the value without a time zone.
|
|
This allows storage and display of values different from the current
|
|
<varname>TimeZone</varname> setting. The third example converts
|
|
Tokyo time to Chicago time. The fourth example shifts the time stamp
|
|
with time zone value to the time zone currently specified by the
|
|
<varname>TimeZone</varname> setting and returns the value without a
|
|
time zone.
|
|
</para>
|
|
|
|
<para>
|
|
The fifth example is a cautionary tale. Due to the fact that there is no
|
|
date associated with the input value, the conversion is made using the
|
|
current date of the session. Therefore, this static example may show a wrong
|
|
result depending on the time of the year it is viewed because
|
|
<literal>'America/Los_Angeles'</literal> observes Daylight Savings Time.
|
|
</para>
|
|
|
|
<para>
|
|
The function <literal><function>timezone</function>(<replaceable>zone</replaceable>,
|
|
<replaceable>timestamp</replaceable>)</literal> is equivalent to the SQL-conforming construct
|
|
<literal><replaceable>timestamp</replaceable> AT TIME ZONE
|
|
<replaceable>zone</replaceable></literal>.
|
|
</para>
|
|
|
|
<para>
|
|
The function <literal><function>timezone</function>(<replaceable>zone</replaceable>,
|
|
<replaceable>time</replaceable>)</literal> is equivalent to the SQL-conforming construct
|
|
<literal><replaceable>time</replaceable> AT TIME ZONE
|
|
<replaceable>zone</replaceable></literal>.
|
|
</para>
|
|
|
|
<para>
|
|
The function <literal><function>timezone</function>(<replaceable>timestamp</replaceable>)</literal>
|
|
is equivalent to the SQL-conforming construct <literal><replaceable>timestamp</replaceable>
|
|
AT LOCAL</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
The function <literal><function>timezone</function>(<replaceable>time</replaceable>)</literal>
|
|
is equivalent to the SQL-conforming construct <literal><replaceable>time</replaceable>
|
|
AT LOCAL</literal>.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-datetime-current">
|
|
<title>Current Date/Time</title>
|
|
|
|
<indexterm>
|
|
<primary>date</primary>
|
|
<secondary>current</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>time</primary>
|
|
<secondary>current</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> provides a number of functions
|
|
that return values related to the current date and time. These
|
|
SQL-standard functions all return values based on the start time of
|
|
the current transaction:
|
|
<synopsis>
|
|
CURRENT_DATE
|
|
CURRENT_TIME
|
|
CURRENT_TIMESTAMP
|
|
CURRENT_TIME(<replaceable>precision</replaceable>)
|
|
CURRENT_TIMESTAMP(<replaceable>precision</replaceable>)
|
|
LOCALTIME
|
|
LOCALTIMESTAMP
|
|
LOCALTIME(<replaceable>precision</replaceable>)
|
|
LOCALTIMESTAMP(<replaceable>precision</replaceable>)
|
|
</synopsis>
|
|
</para>
|
|
|
|
<para>
|
|
<function>CURRENT_TIME</function> and
|
|
<function>CURRENT_TIMESTAMP</function> deliver values with time zone;
|
|
<function>LOCALTIME</function> and
|
|
<function>LOCALTIMESTAMP</function> deliver values without time zone.
|
|
</para>
|
|
|
|
<para>
|
|
<function>CURRENT_TIME</function>,
|
|
<function>CURRENT_TIMESTAMP</function>,
|
|
<function>LOCALTIME</function>, and
|
|
<function>LOCALTIMESTAMP</function>
|
|
can optionally take
|
|
a precision parameter, which causes the result to be rounded
|
|
to that many fractional digits in the seconds field. Without a precision parameter,
|
|
the result is given to the full available precision.
|
|
</para>
|
|
|
|
<para>
|
|
Some examples:
|
|
<screen>
|
|
SELECT CURRENT_TIME;
|
|
<lineannotation>Result: </lineannotation><computeroutput>14:39:53.662522-05</computeroutput>
|
|
SELECT CURRENT_DATE;
|
|
<lineannotation>Result: </lineannotation><computeroutput>2019-12-23</computeroutput>
|
|
SELECT CURRENT_TIMESTAMP;
|
|
<lineannotation>Result: </lineannotation><computeroutput>2019-12-23 14:39:53.662522-05</computeroutput>
|
|
SELECT CURRENT_TIMESTAMP(2);
|
|
<lineannotation>Result: </lineannotation><computeroutput>2019-12-23 14:39:53.66-05</computeroutput>
|
|
SELECT LOCALTIMESTAMP;
|
|
<lineannotation>Result: </lineannotation><computeroutput>2019-12-23 14:39:53.662522</computeroutput>
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
Since these functions return
|
|
the start time of the current transaction, their values do not
|
|
change during the transaction. This is considered a feature:
|
|
the intent is to allow a single transaction to have a consistent
|
|
notion of the <quote>current</quote> time, so that multiple
|
|
modifications within the same transaction bear the same
|
|
time stamp.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
Other database systems might advance these values more
|
|
frequently.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> also provides functions that
|
|
return the start time of the current statement, as well as the actual
|
|
current time at the instant the function is called. The complete list
|
|
of non-SQL-standard time functions is:
|
|
<synopsis>
|
|
transaction_timestamp()
|
|
statement_timestamp()
|
|
clock_timestamp()
|
|
timeofday()
|
|
now()
|
|
</synopsis>
|
|
</para>
|
|
|
|
<para>
|
|
<function>transaction_timestamp()</function> is equivalent to
|
|
<function>CURRENT_TIMESTAMP</function>, but is named to clearly reflect
|
|
what it returns.
|
|
<function>statement_timestamp()</function> returns the start time of the current
|
|
statement (more specifically, the time of receipt of the latest command
|
|
message from the client).
|
|
<function>statement_timestamp()</function> and <function>transaction_timestamp()</function>
|
|
return the same value during the first command of a transaction, but might
|
|
differ during subsequent commands.
|
|
<function>clock_timestamp()</function> returns the actual current time, and
|
|
therefore its value changes even within a single SQL command.
|
|
<function>timeofday()</function> is a historical
|
|
<productname>PostgreSQL</productname> function. Like
|
|
<function>clock_timestamp()</function>, it returns the actual current time,
|
|
but as a formatted <type>text</type> string rather than a <type>timestamp
|
|
with time zone</type> value.
|
|
<function>now()</function> is a traditional <productname>PostgreSQL</productname>
|
|
equivalent to <function>transaction_timestamp()</function>.
|
|
</para>
|
|
|
|
<para>
|
|
All the date/time data types also accept the special literal value
|
|
<literal>now</literal> to specify the current date and time (again,
|
|
interpreted as the transaction start time). Thus,
|
|
the following three all return the same result:
|
|
<programlisting>
|
|
SELECT CURRENT_TIMESTAMP;
|
|
SELECT now();
|
|
SELECT TIMESTAMP 'now'; -- but see tip below
|
|
</programlisting>
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
Do not use the third form when specifying a value to be evaluated later,
|
|
for example in a <literal>DEFAULT</literal> clause for a table column.
|
|
The system will convert <literal>now</literal>
|
|
to a <type>timestamp</type> as soon as the constant is parsed, so that when
|
|
the default value is needed,
|
|
the time of the table creation would be used! The first two
|
|
forms will not be evaluated until the default value is used,
|
|
because they are function calls. Thus they will give the desired
|
|
behavior of defaulting to the time of row insertion.
|
|
(See also <xref linkend="datatype-datetime-special-values"/>.)
|
|
</para>
|
|
</tip>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-datetime-delay">
|
|
<title>Delaying Execution</title>
|
|
|
|
<indexterm>
|
|
<primary>pg_sleep</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>pg_sleep_for</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>pg_sleep_until</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>sleep</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>delay</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The following functions are available to delay execution of the server
|
|
process:
|
|
<synopsis>
|
|
pg_sleep ( <type>double precision</type> )
|
|
pg_sleep_for ( <type>interval</type> )
|
|
pg_sleep_until ( <type>timestamp with time zone</type> )
|
|
</synopsis>
|
|
|
|
<function>pg_sleep</function> makes the current session's process
|
|
sleep until the given number of seconds have
|
|
elapsed. Fractional-second delays can be specified.
|
|
<function>pg_sleep_for</function> is a convenience function to
|
|
allow the sleep time to be specified as an <type>interval</type>.
|
|
<function>pg_sleep_until</function> is a convenience function for when
|
|
a specific wake-up time is desired.
|
|
For example:
|
|
|
|
<programlisting>
|
|
SELECT pg_sleep(1.5);
|
|
SELECT pg_sleep_for('5 minutes');
|
|
SELECT pg_sleep_until('tomorrow 03:00');
|
|
</programlisting>
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
The effective resolution of the sleep interval is platform-specific;
|
|
0.01 seconds is a common value. The sleep delay will be at least as long
|
|
as specified. It might be longer depending on factors such as server load.
|
|
In particular, <function>pg_sleep_until</function> is not guaranteed to
|
|
wake up exactly at the specified time, but it will not wake up any earlier.
|
|
</para>
|
|
</note>
|
|
|
|
<warning>
|
|
<para>
|
|
Make sure that your session does not hold more locks than necessary
|
|
when calling <function>pg_sleep</function> or its variants. Otherwise
|
|
other sessions might have to wait for your sleeping process, slowing down
|
|
the entire system.
|
|
</para>
|
|
</warning>
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-enum">
|
|
<title>Enum Support Functions</title>
|
|
|
|
<para>
|
|
For enum types (described in <xref linkend="datatype-enum"/>),
|
|
there are several functions that allow cleaner programming without
|
|
hard-coding particular values of an enum type.
|
|
These are listed in <xref linkend="functions-enum-table"/>. The examples
|
|
assume an enum type created as:
|
|
|
|
<programlisting>
|
|
CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple');
|
|
</programlisting>
|
|
|
|
</para>
|
|
|
|
<table id="functions-enum-table">
|
|
<title>Enum Support Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>enum_first</primary>
|
|
</indexterm>
|
|
<function>enum_first</function> ( <type>anyenum</type> )
|
|
<returnvalue>anyenum</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the first value of the input enum type.
|
|
</para>
|
|
<para>
|
|
<literal>enum_first(null::rainbow)</literal>
|
|
<returnvalue>red</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>enum_last</primary>
|
|
</indexterm>
|
|
<function>enum_last</function> ( <type>anyenum</type> )
|
|
<returnvalue>anyenum</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the last value of the input enum type.
|
|
</para>
|
|
<para>
|
|
<literal>enum_last(null::rainbow)</literal>
|
|
<returnvalue>purple</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>enum_range</primary>
|
|
</indexterm>
|
|
<function>enum_range</function> ( <type>anyenum</type> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns all values of the input enum type in an ordered array.
|
|
</para>
|
|
<para>
|
|
<literal>enum_range(null::rainbow)</literal>
|
|
<returnvalue>{red,orange,yellow,&zwsp;green,blue,purple}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>enum_range</function> ( <type>anyenum</type>, <type>anyenum</type> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the range between the two given enum values, as an ordered
|
|
array. The values must be from the same enum type. If the first
|
|
parameter is null, the result will start with the first value of
|
|
the enum type.
|
|
If the second parameter is null, the result will end with the last
|
|
value of the enum type.
|
|
</para>
|
|
<para>
|
|
<literal>enum_range('orange'::rainbow, 'green'::rainbow)</literal>
|
|
<returnvalue>{orange,yellow,green}</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>enum_range(NULL, 'green'::rainbow)</literal>
|
|
<returnvalue>{red,orange,&zwsp;yellow,green}</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>enum_range('orange'::rainbow, NULL)</literal>
|
|
<returnvalue>{orange,yellow,green,&zwsp;blue,purple}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Notice that except for the two-argument form of <function>enum_range</function>,
|
|
these functions disregard the specific value passed to them; they care
|
|
only about its declared data type. Either null or a specific value of
|
|
the type can be passed, with the same result. It is more common to
|
|
apply these functions to a table column or function argument than to
|
|
a hardwired type name as used in the examples.
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-geometry">
|
|
<title>Geometric Functions and Operators</title>
|
|
|
|
<para>
|
|
The geometric types <type>point</type>, <type>box</type>,
|
|
<type>lseg</type>, <type>line</type>, <type>path</type>,
|
|
<type>polygon</type>, and <type>circle</type> have a large set of
|
|
native support functions and operators, shown in <xref
|
|
linkend="functions-geometry-op-table"/>, <xref
|
|
linkend="functions-geometry-func-table"/>, and <xref
|
|
linkend="functions-geometry-conv-table"/>.
|
|
</para>
|
|
|
|
<table id="functions-geometry-op-table">
|
|
<title>Geometric Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>+</literal> <type>point</type>
|
|
<returnvalue><replaceable>geometric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Adds the coordinates of the second <type>point</type> to those of each
|
|
point of the first argument, thus performing translation.
|
|
Available for <type>point</type>, <type>box</type>, <type>path</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>box '(1,1),(0,0)' + point '(2,0)'</literal>
|
|
<returnvalue>(3,1),(2,0)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>path</type> <literal>+</literal> <type>path</type>
|
|
<returnvalue>path</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates two open paths (returns NULL if either path is closed).
|
|
</para>
|
|
<para>
|
|
<literal>path '[(0,0),(1,1)]' + path '[(2,2),(3,3),(4,4)]'</literal>
|
|
<returnvalue>[(0,0),(1,1),(2,2),(3,3),(4,4)]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>-</literal> <type>point</type>
|
|
<returnvalue><replaceable>geometric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtracts the coordinates of the second <type>point</type> from those
|
|
of each point of the first argument, thus performing translation.
|
|
Available for <type>point</type>, <type>box</type>, <type>path</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>box '(1,1),(0,0)' - point '(2,0)'</literal>
|
|
<returnvalue>(-1,1),(-2,0)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>*</literal> <type>point</type>
|
|
<returnvalue><replaceable>geometric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Multiplies each point of the first argument by the second
|
|
<type>point</type> (treating a point as being a complex number
|
|
represented by real and imaginary parts, and performing standard
|
|
complex multiplication). If one interprets
|
|
the second <type>point</type> as a vector, this is equivalent to
|
|
scaling the object's size and distance from the origin by the length
|
|
of the vector, and rotating it counterclockwise around the origin by
|
|
the vector's angle from the <replaceable>x</replaceable> axis.
|
|
Available for <type>point</type>, <type>box</type>,<footnote
|
|
id="functions-geometry-rotation-fn"><para><quote>Rotating</quote> a
|
|
box with these operators only moves its corner points: the box is
|
|
still considered to have sides parallel to the axes. Hence the box's
|
|
size is not preserved, as a true rotation would do.</para></footnote>
|
|
<type>path</type>, <type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>path '((0,0),(1,0),(1,1))' * point '(3.0,0)'</literal>
|
|
<returnvalue>((0,0),(3,0),(3,3))</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>path '((0,0),(1,0),(1,1))' * point(cosd(45), sind(45))</literal>
|
|
<returnvalue>((0,0),&zwsp;(0.7071067811865475,0.7071067811865475),&zwsp;(0,1.414213562373095))</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>/</literal> <type>point</type>
|
|
<returnvalue><replaceable>geometric_type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Divides each point of the first argument by the second
|
|
<type>point</type> (treating a point as being a complex number
|
|
represented by real and imaginary parts, and performing standard
|
|
complex division). If one interprets
|
|
the second <type>point</type> as a vector, this is equivalent to
|
|
scaling the object's size and distance from the origin down by the
|
|
length of the vector, and rotating it clockwise around the origin by
|
|
the vector's angle from the <replaceable>x</replaceable> axis.
|
|
Available for <type>point</type>, <type>box</type>,<footnoteref
|
|
linkend="functions-geometry-rotation-fn"/> <type>path</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>path '((0,0),(1,0),(1,1))' / point '(2.0,0)'</literal>
|
|
<returnvalue>((0,0),(0.5,0),(0.5,0.5))</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>path '((0,0),(1,0),(1,1))' / point(cosd(45), sind(45))</literal>
|
|
<returnvalue>((0,0),&zwsp;(0.7071067811865476,-0.7071067811865476),&zwsp;(1.4142135623730951,0))</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>@-@</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the total length.
|
|
Available for <type>lseg</type>, <type>path</type>.
|
|
</para>
|
|
<para>
|
|
<literal>@-@ path '[(0,0),(1,0),(1,1)]'</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>@@</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>point</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the center point.
|
|
Available for <type>box</type>, <type>lseg</type>,
|
|
<type>polygon</type>, <type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>@@ box '(2,2),(0,0)'</literal>
|
|
<returnvalue>(1,1)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>#</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of points.
|
|
Available for <type>path</type>, <type>polygon</type>.
|
|
</para>
|
|
<para>
|
|
<literal># path '((1,0),(0,1),(-1,0))'</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>#</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>point</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the point of intersection, or NULL if there is none.
|
|
Available for <type>lseg</type>, <type>line</type>.
|
|
</para>
|
|
<para>
|
|
<literal>lseg '[(0,0),(1,1)]' # lseg '[(1,0),(0,1)]'</literal>
|
|
<returnvalue>(0.5,0.5)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>box</type> <literal>#</literal> <type>box</type>
|
|
<returnvalue>box</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the intersection of two boxes, or NULL if there is none.
|
|
</para>
|
|
<para>
|
|
<literal>box '(2,2),(-1,-1)' # box '(1,1),(-2,-2)'</literal>
|
|
<returnvalue>(1,1),(-1,-1)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>##</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>point</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the closest point to the first object on the second object.
|
|
Available for these pairs of types:
|
|
(<type>point</type>, <type>box</type>),
|
|
(<type>point</type>, <type>lseg</type>),
|
|
(<type>point</type>, <type>line</type>),
|
|
(<type>lseg</type>, <type>box</type>),
|
|
(<type>lseg</type>, <type>lseg</type>),
|
|
(<type>line</type>, <type>lseg</type>).
|
|
</para>
|
|
<para>
|
|
<literal>point '(0,0)' ## lseg '[(2,0),(0,2)]'</literal>
|
|
<returnvalue>(1,1)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal><-></literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the distance between the objects.
|
|
Available for all seven geometric types, for all combinations
|
|
of <type>point</type> with another geometric type, and for
|
|
these additional pairs of types:
|
|
(<type>box</type>, <type>lseg</type>),
|
|
(<type>lseg</type>, <type>line</type>),
|
|
(<type>polygon</type>, <type>circle</type>)
|
|
(and the commutator cases).
|
|
</para>
|
|
<para>
|
|
<literal>circle '<(0,0),1>' <-> circle '<(5,0),1>'</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>@></literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does first object contain second?
|
|
Available for these pairs of types:
|
|
(<literal>box</literal>, <literal>point</literal>),
|
|
(<literal>box</literal>, <literal>box</literal>),
|
|
(<literal>path</literal>, <literal>point</literal>),
|
|
(<literal>polygon</literal>, <literal>point</literal>),
|
|
(<literal>polygon</literal>, <literal>polygon</literal>),
|
|
(<literal>circle</literal>, <literal>point</literal>),
|
|
(<literal>circle</literal>, <literal>circle</literal>).
|
|
</para>
|
|
<para>
|
|
<literal>circle '<(0,0),2>' @> point '(1,1)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal><@</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is first object contained in or on second?
|
|
Available for these pairs of types:
|
|
(<literal>point</literal>, <literal>box</literal>),
|
|
(<literal>point</literal>, <literal>lseg</literal>),
|
|
(<literal>point</literal>, <literal>line</literal>),
|
|
(<literal>point</literal>, <literal>path</literal>),
|
|
(<literal>point</literal>, <literal>polygon</literal>),
|
|
(<literal>point</literal>, <literal>circle</literal>),
|
|
(<literal>box</literal>, <literal>box</literal>),
|
|
(<literal>lseg</literal>, <literal>box</literal>),
|
|
(<literal>lseg</literal>, <literal>line</literal>),
|
|
(<literal>polygon</literal>, <literal>polygon</literal>),
|
|
(<literal>circle</literal>, <literal>circle</literal>).
|
|
</para>
|
|
<para>
|
|
<literal>point '(1,1)' <@ circle '<(0,0),2>'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>&&</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Do these objects overlap? (One point in common makes this true.)
|
|
Available for <type>box</type>, <type>polygon</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>box '(1,1),(0,0)' && box '(2,2),(0,0)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal><<</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is first object strictly left of second?
|
|
Available for <type>point</type>, <type>box</type>,
|
|
<type>polygon</type>, <type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>circle '<(0,0),1>' << circle '<(5,0),1>'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>>></literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is first object strictly right of second?
|
|
Available for <type>point</type>, <type>box</type>,
|
|
<type>polygon</type>, <type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>circle '<(5,0),1>' >> circle '<(0,0),1>'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>&<</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does first object not extend to the right of second?
|
|
Available for <type>box</type>, <type>polygon</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>box '(1,1),(0,0)' &< box '(2,2),(0,0)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>&></literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does first object not extend to the left of second?
|
|
Available for <type>box</type>, <type>polygon</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>box '(3,3),(0,0)' &> box '(2,2),(0,0)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal><<|</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is first object strictly below second?
|
|
Available for <type>point</type>, <type>box</type>, <type>polygon</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>box '(3,3),(0,0)' <<| box '(5,5),(3,4)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>|>></literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is first object strictly above second?
|
|
Available for <type>point</type>, <type>box</type>, <type>polygon</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>box '(5,5),(3,4)' |>> box '(3,3),(0,0)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>&<|</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does first object not extend above second?
|
|
Available for <type>box</type>, <type>polygon</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>box '(1,1),(0,0)' &<| box '(2,2),(0,0)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>|&></literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does first object not extend below second?
|
|
Available for <type>box</type>, <type>polygon</type>,
|
|
<type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>box '(3,3),(0,0)' |&> box '(2,2),(0,0)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>box</type> <literal><^</literal> <type>box</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is first object below second (allows edges to touch)?
|
|
</para>
|
|
<para>
|
|
<literal>box '((1,1),(0,0))' <^ box '((2,2),(1,1))'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>box</type> <literal>>^</literal> <type>box</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is first object above second (allows edges to touch)?
|
|
</para>
|
|
<para>
|
|
<literal>box '((2,2),(1,1))' >^ box '((1,1),(0,0))'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>?#</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Do these objects intersect?
|
|
Available for these pairs of types:
|
|
(<type>box</type>, <type>box</type>),
|
|
(<type>lseg</type>, <type>box</type>),
|
|
(<type>lseg</type>, <type>lseg</type>),
|
|
(<type>lseg</type>, <type>line</type>),
|
|
(<type>line</type>, <type>box</type>),
|
|
(<type>line</type>, <type>line</type>),
|
|
(<type>path</type>, <type>path</type>).
|
|
</para>
|
|
<para>
|
|
<literal>lseg '[(-1,0),(1,0)]' ?# box '(2,2),(-2,-2)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>?-</literal> <type>line</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<literal>?-</literal> <type>lseg</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is line horizontal?
|
|
</para>
|
|
<para>
|
|
<literal>?- lseg '[(-1,0),(1,0)]'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>point</type> <literal>?-</literal> <type>point</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Are points horizontally aligned (that is, have same y coordinate)?
|
|
</para>
|
|
<para>
|
|
<literal>point '(1,0)' ?- point '(0,0)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>?|</literal> <type>line</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<literal>?|</literal> <type>lseg</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is line vertical?
|
|
</para>
|
|
<para>
|
|
<literal>?| lseg '[(-1,0),(1,0)]'</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>point</type> <literal>?|</literal> <type>point</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Are points vertically aligned (that is, have same x coordinate)?
|
|
</para>
|
|
<para>
|
|
<literal>point '(0,1)' ?| point '(0,0)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>line</type> <literal>?-|</literal> <type>line</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>lseg</type> <literal>?-|</literal> <type>lseg</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Are lines perpendicular?
|
|
</para>
|
|
<para>
|
|
<literal>lseg '[(0,0),(0,1)]' ?-| lseg '[(0,0),(1,0)]'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>line</type> <literal>?||</literal> <type>line</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>lseg</type> <literal>?||</literal> <type>lseg</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Are lines parallel?
|
|
</para>
|
|
<para>
|
|
<literal>lseg '[(-1,0),(1,0)]' ?|| lseg '[(-1,2),(1,2)]'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>geometric_type</replaceable> <literal>~=</literal> <replaceable>geometric_type</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Are these objects the same?
|
|
Available for <type>point</type>, <type>box</type>,
|
|
<type>polygon</type>, <type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>polygon '((0,0),(1,1))' ~= polygon '((1,1),(0,0))'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<caution>
|
|
<para>
|
|
Note that the <quote>same as</quote> operator, <literal>~=</literal>,
|
|
represents the usual notion of equality for the <type>point</type>,
|
|
<type>box</type>, <type>polygon</type>, and <type>circle</type> types.
|
|
Some of the geometric types also have an <literal>=</literal> operator, but
|
|
<literal>=</literal> compares for equal <emphasis>areas</emphasis> only.
|
|
The other scalar comparison operators (<literal><=</literal> and so
|
|
on), where available for these types, likewise compare areas.
|
|
</para>
|
|
</caution>
|
|
|
|
<note>
|
|
<para>
|
|
Before <productname>PostgreSQL</productname> 14, the point
|
|
is strictly below/above comparison operators <type>point</type>
|
|
<literal><<|</literal> <type>point</type> and <type>point</type>
|
|
<literal>|>></literal> <type>point</type> were respectively
|
|
called <literal><^</literal> and <literal>>^</literal>. These
|
|
names are still available, but are deprecated and will eventually be
|
|
removed.
|
|
</para>
|
|
</note>
|
|
|
|
<table id="functions-geometry-func-table">
|
|
<title>Geometric Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>area</primary>
|
|
</indexterm>
|
|
<function>area</function> ( <replaceable>geometric_type</replaceable> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes area.
|
|
Available for <type>box</type>, <type>path</type>, <type>circle</type>.
|
|
A <type>path</type> input must be closed, else NULL is returned.
|
|
Also, if the <type>path</type> is self-intersecting, the result may be
|
|
meaningless.
|
|
</para>
|
|
<para>
|
|
<literal>area(box '(2,2),(0,0)')</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>center</primary>
|
|
</indexterm>
|
|
<function>center</function> ( <replaceable>geometric_type</replaceable> )
|
|
<returnvalue>point</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes center point.
|
|
Available for <type>box</type>, <type>circle</type>.
|
|
</para>
|
|
<para>
|
|
<literal>center(box '(1,2),(0,0)')</literal>
|
|
<returnvalue>(0.5,1)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>diagonal</primary>
|
|
</indexterm>
|
|
<function>diagonal</function> ( <type>box</type> )
|
|
<returnvalue>lseg</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts box's diagonal as a line segment
|
|
(same as <function>lseg(box)</function>).
|
|
</para>
|
|
<para>
|
|
<literal>diagonal(box '(1,2),(0,0)')</literal>
|
|
<returnvalue>[(1,2),(0,0)]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>diameter</primary>
|
|
</indexterm>
|
|
<function>diameter</function> ( <type>circle</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes diameter of circle.
|
|
</para>
|
|
<para>
|
|
<literal>diameter(circle '<(0,0),2>')</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>height</primary>
|
|
</indexterm>
|
|
<function>height</function> ( <type>box</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes vertical size of box.
|
|
</para>
|
|
<para>
|
|
<literal>height(box '(1,2),(0,0)')</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>isclosed</primary>
|
|
</indexterm>
|
|
<function>isclosed</function> ( <type>path</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is path closed?
|
|
</para>
|
|
<para>
|
|
<literal>isclosed(path '((0,0),(1,1),(2,0))')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>isopen</primary>
|
|
</indexterm>
|
|
<function>isopen</function> ( <type>path</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is path open?
|
|
</para>
|
|
<para>
|
|
<literal>isopen(path '[(0,0),(1,1),(2,0)]')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>length</primary>
|
|
</indexterm>
|
|
<function>length</function> ( <replaceable>geometric_type</replaceable> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the total length.
|
|
Available for <type>lseg</type>, <type>path</type>.
|
|
</para>
|
|
<para>
|
|
<literal>length(path '((-1,0),(1,0))')</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>npoints</primary>
|
|
</indexterm>
|
|
<function>npoints</function> ( <replaceable>geometric_type</replaceable> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of points.
|
|
Available for <type>path</type>, <type>polygon</type>.
|
|
</para>
|
|
<para>
|
|
<literal>npoints(path '[(0,0),(1,1),(2,0)]')</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pclose</primary>
|
|
</indexterm>
|
|
<function>pclose</function> ( <type>path</type> )
|
|
<returnvalue>path</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts path to closed form.
|
|
</para>
|
|
<para>
|
|
<literal>pclose(path '[(0,0),(1,1),(2,0)]')</literal>
|
|
<returnvalue>((0,0),(1,1),(2,0))</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>popen</primary>
|
|
</indexterm>
|
|
<function>popen</function> ( <type>path</type> )
|
|
<returnvalue>path</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts path to open form.
|
|
</para>
|
|
<para>
|
|
<literal>popen(path '((0,0),(1,1),(2,0))')</literal>
|
|
<returnvalue>[(0,0),(1,1),(2,0)]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>radius</primary>
|
|
</indexterm>
|
|
<function>radius</function> ( <type>circle</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes radius of circle.
|
|
</para>
|
|
<para>
|
|
<literal>radius(circle '<(0,0),2>')</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>slope</primary>
|
|
</indexterm>
|
|
<function>slope</function> ( <type>point</type>, <type>point</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes slope of a line drawn through the two points.
|
|
</para>
|
|
<para>
|
|
<literal>slope(point '(0,0)', point '(2,1)')</literal>
|
|
<returnvalue>0.5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>width</primary>
|
|
</indexterm>
|
|
<function>width</function> ( <type>box</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes horizontal size of box.
|
|
</para>
|
|
<para>
|
|
<literal>width(box '(1,2),(0,0)')</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-geometry-conv-table">
|
|
<title>Geometric Type Conversion Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>box</primary>
|
|
</indexterm>
|
|
<function>box</function> ( <type>circle</type> )
|
|
<returnvalue>box</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes box inscribed within the circle.
|
|
</para>
|
|
<para>
|
|
<literal>box(circle '<(0,0),2>')</literal>
|
|
<returnvalue>(1.414213562373095,1.414213562373095),&zwsp;(-1.414213562373095,-1.414213562373095)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>box</function> ( <type>point</type> )
|
|
<returnvalue>box</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts point to empty box.
|
|
</para>
|
|
<para>
|
|
<literal>box(point '(1,0)')</literal>
|
|
<returnvalue>(1,0),(1,0)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>box</function> ( <type>point</type>, <type>point</type> )
|
|
<returnvalue>box</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts any two corner points to box.
|
|
</para>
|
|
<para>
|
|
<literal>box(point '(0,1)', point '(1,0)')</literal>
|
|
<returnvalue>(1,1),(0,0)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>box</function> ( <type>polygon</type> )
|
|
<returnvalue>box</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes bounding box of polygon.
|
|
</para>
|
|
<para>
|
|
<literal>box(polygon '((0,0),(1,1),(2,0))')</literal>
|
|
<returnvalue>(2,1),(0,0)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bound_box</primary>
|
|
</indexterm>
|
|
<function>bound_box</function> ( <type>box</type>, <type>box</type> )
|
|
<returnvalue>box</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes bounding box of two boxes.
|
|
</para>
|
|
<para>
|
|
<literal>bound_box(box '(1,1),(0,0)', box '(4,4),(3,3)')</literal>
|
|
<returnvalue>(4,4),(0,0)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>circle</primary>
|
|
</indexterm>
|
|
<function>circle</function> ( <type>box</type> )
|
|
<returnvalue>circle</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes smallest circle enclosing box.
|
|
</para>
|
|
<para>
|
|
<literal>circle(box '(1,1),(0,0)')</literal>
|
|
<returnvalue><(0.5,0.5),0.7071067811865476></returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>circle</function> ( <type>point</type>, <type>double precision</type> )
|
|
<returnvalue>circle</returnvalue>
|
|
</para>
|
|
<para>
|
|
Constructs circle from center and radius.
|
|
</para>
|
|
<para>
|
|
<literal>circle(point '(0,0)', 2.0)</literal>
|
|
<returnvalue><(0,0),2></returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>circle</function> ( <type>polygon</type> )
|
|
<returnvalue>circle</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts polygon to circle. The circle's center is the mean of the
|
|
positions of the polygon's points, and the radius is the average
|
|
distance of the polygon's points from that center.
|
|
</para>
|
|
<para>
|
|
<literal>circle(polygon '((0,0),(1,3),(2,0))')</literal>
|
|
<returnvalue><(1,1),1.6094757082487299></returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>line</primary>
|
|
</indexterm>
|
|
<function>line</function> ( <type>point</type>, <type>point</type> )
|
|
<returnvalue>line</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts two points to the line through them.
|
|
</para>
|
|
<para>
|
|
<literal>line(point '(-1,0)', point '(1,0)')</literal>
|
|
<returnvalue>{0,-1,0}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lseg</primary>
|
|
</indexterm>
|
|
<function>lseg</function> ( <type>box</type> )
|
|
<returnvalue>lseg</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts box's diagonal as a line segment.
|
|
</para>
|
|
<para>
|
|
<literal>lseg(box '(1,0),(-1,0)')</literal>
|
|
<returnvalue>[(1,0),(-1,0)]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>lseg</function> ( <type>point</type>, <type>point</type> )
|
|
<returnvalue>lseg</returnvalue>
|
|
</para>
|
|
<para>
|
|
Constructs line segment from two endpoints.
|
|
</para>
|
|
<para>
|
|
<literal>lseg(point '(-1,0)', point '(1,0)')</literal>
|
|
<returnvalue>[(-1,0),(1,0)]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>path</primary>
|
|
</indexterm>
|
|
<function>path</function> ( <type>polygon</type> )
|
|
<returnvalue>path</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts polygon to a closed path with the same list of points.
|
|
</para>
|
|
<para>
|
|
<literal>path(polygon '((0,0),(1,1),(2,0))')</literal>
|
|
<returnvalue>((0,0),(1,1),(2,0))</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>point</primary>
|
|
</indexterm>
|
|
<function>point</function> ( <type>double precision</type>, <type>double precision</type> )
|
|
<returnvalue>point</returnvalue>
|
|
</para>
|
|
<para>
|
|
Constructs point from its coordinates.
|
|
</para>
|
|
<para>
|
|
<literal>point(23.4, -44.5)</literal>
|
|
<returnvalue>(23.4,-44.5)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>point</function> ( <type>box</type> )
|
|
<returnvalue>point</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes center of box.
|
|
</para>
|
|
<para>
|
|
<literal>point(box '(1,0),(-1,0)')</literal>
|
|
<returnvalue>(0,0)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>point</function> ( <type>circle</type> )
|
|
<returnvalue>point</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes center of circle.
|
|
</para>
|
|
<para>
|
|
<literal>point(circle '<(0,0),2>')</literal>
|
|
<returnvalue>(0,0)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>point</function> ( <type>lseg</type> )
|
|
<returnvalue>point</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes center of line segment.
|
|
</para>
|
|
<para>
|
|
<literal>point(lseg '[(-1,0),(1,0)]')</literal>
|
|
<returnvalue>(0,0)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>point</function> ( <type>polygon</type> )
|
|
<returnvalue>point</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes center of polygon (the mean of the
|
|
positions of the polygon's points).
|
|
</para>
|
|
<para>
|
|
<literal>point(polygon '((0,0),(1,1),(2,0))')</literal>
|
|
<returnvalue>(1,0.3333333333333333)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>polygon</primary>
|
|
</indexterm>
|
|
<function>polygon</function> ( <type>box</type> )
|
|
<returnvalue>polygon</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts box to a 4-point polygon.
|
|
</para>
|
|
<para>
|
|
<literal>polygon(box '(1,1),(0,0)')</literal>
|
|
<returnvalue>((0,0),(0,1),(1,1),(1,0))</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>polygon</function> ( <type>circle</type> )
|
|
<returnvalue>polygon</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts circle to a 12-point polygon.
|
|
</para>
|
|
<para>
|
|
<literal>polygon(circle '<(0,0),2>')</literal>
|
|
<returnvalue>((-2,0),&zwsp;(-1.7320508075688774,0.9999999999999999),&zwsp;(-1.0000000000000002,1.7320508075688772),&zwsp;(-1.2246063538223773e-16,2),&zwsp;(0.9999999999999996,1.7320508075688774),&zwsp;(1.732050807568877,1.0000000000000007),&zwsp;(2,2.4492127076447545e-16),&zwsp;(1.7320508075688776,-0.9999999999999994),&zwsp;(1.0000000000000009,-1.7320508075688767),&zwsp;(3.673819061467132e-16,-2),&zwsp;(-0.9999999999999987,-1.732050807568878),&zwsp;(-1.7320508075688767,-1.0000000000000009))</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>polygon</function> ( <type>integer</type>, <type>circle</type> )
|
|
<returnvalue>polygon</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts circle to an <replaceable>n</replaceable>-point polygon.
|
|
</para>
|
|
<para>
|
|
<literal>polygon(4, circle '<(3,0),1>')</literal>
|
|
<returnvalue>((2,0),&zwsp;(3,1),&zwsp;(4,1.2246063538223773e-16),&zwsp;(3,-1))</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>polygon</function> ( <type>path</type> )
|
|
<returnvalue>polygon</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts closed path to a polygon with the same list of points.
|
|
</para>
|
|
<para>
|
|
<literal>polygon(path '((0,0),(1,1),(2,0))')</literal>
|
|
<returnvalue>((0,0),(1,1),(2,0))</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
It is possible to access the two component numbers of a <type>point</type>
|
|
as though the point were an array with indexes 0 and 1. For example, if
|
|
<literal>t.p</literal> is a <type>point</type> column then
|
|
<literal>SELECT p[0] FROM t</literal> retrieves the X coordinate and
|
|
<literal>UPDATE t SET p[1] = ...</literal> changes the Y coordinate.
|
|
In the same way, a value of type <type>box</type> or <type>lseg</type> can be treated
|
|
as an array of two <type>point</type> values.
|
|
</para>
|
|
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-net">
|
|
<title>Network Address Functions and Operators</title>
|
|
|
|
<para>
|
|
The IP network address types, <type>cidr</type> and <type>inet</type>,
|
|
support the usual comparison operators shown in
|
|
<xref linkend="functions-comparison-op-table"/>
|
|
as well as the specialized operators and functions shown in
|
|
<xref linkend="cidr-inet-operators-table"/> and
|
|
<xref linkend="cidr-inet-functions-table"/>.
|
|
</para>
|
|
|
|
<para>
|
|
Any <type>cidr</type> value can be cast to <type>inet</type> implicitly;
|
|
therefore, the operators and functions shown below as operating on
|
|
<type>inet</type> also work on <type>cidr</type> values. (Where there are
|
|
separate functions for <type>inet</type> and <type>cidr</type>, it is
|
|
because the behavior should be different for the two cases.)
|
|
Also, it is permitted to cast an <type>inet</type> value
|
|
to <type>cidr</type>. When this is done, any bits to the right of the
|
|
netmask are silently zeroed to create a valid <type>cidr</type> value.
|
|
</para>
|
|
|
|
<table id="cidr-inet-operators-table">
|
|
<title>IP Address Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal><<</literal> <type>inet</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is subnet strictly contained by subnet?
|
|
This operator, and the next four, test for subnet inclusion. They
|
|
consider only the network parts of the two addresses (ignoring any
|
|
bits to the right of the netmasks) and determine whether one network
|
|
is identical to or a subnet of the other.
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1.5' << inet '192.168.1/24'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.0.5' << inet '192.168.1/24'</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1/24' << inet '192.168.1/24'</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal><<=</literal> <type>inet</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is subnet contained by or equal to subnet?
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1/24' <<= inet '192.168.1/24'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal>>></literal> <type>inet</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does subnet strictly contain subnet?
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1/24' >> inet '192.168.1.5'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal>>>=</literal> <type>inet</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does subnet contain or equal subnet?
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1/24' >>= inet '192.168.1/24'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal>&&</literal> <type>inet</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does either subnet contain or equal the other?
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1/24' && inet '192.168.1.80/28'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1/24' && inet '192.168.2.0/28'</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>~</literal> <type>inet</type>
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes bitwise NOT.
|
|
</para>
|
|
<para>
|
|
<literal>~ inet '192.168.1.6'</literal>
|
|
<returnvalue>63.87.254.249</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal>&</literal> <type>inet</type>
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes bitwise AND.
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1.6' & inet '0.0.0.255'</literal>
|
|
<returnvalue>0.0.0.6</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal>|</literal> <type>inet</type>
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes bitwise OR.
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1.6' | inet '0.0.0.255'</literal>
|
|
<returnvalue>192.168.1.255</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal>+</literal> <type>bigint</type>
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Adds an offset to an address.
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1.6' + 25</literal>
|
|
<returnvalue>192.168.1.31</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>bigint</type> <literal>+</literal> <type>inet</type>
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Adds an offset to an address.
|
|
</para>
|
|
<para>
|
|
<literal>200 + inet '::ffff:fff0:1'</literal>
|
|
<returnvalue>::ffff:255.240.0.201</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal>-</literal> <type>bigint</type>
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtracts an offset from an address.
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1.43' - 36</literal>
|
|
<returnvalue>192.168.1.7</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>inet</type> <literal>-</literal> <type>inet</type>
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the difference of two addresses.
|
|
</para>
|
|
<para>
|
|
<literal>inet '192.168.1.43' - inet '192.168.1.19'</literal>
|
|
<returnvalue>24</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>inet '::1' - inet '::ffff:1'</literal>
|
|
<returnvalue>-4294901760</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="cidr-inet-functions-table">
|
|
<title>IP Address Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>abbrev</primary>
|
|
</indexterm>
|
|
<function>abbrev</function> ( <type>inet</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Creates an abbreviated display format as text.
|
|
(The result is the same as the <type>inet</type> output function
|
|
produces; it is <quote>abbreviated</quote> only in comparison to the
|
|
result of an explicit cast to <type>text</type>, which for historical
|
|
reasons will never suppress the netmask part.)
|
|
</para>
|
|
<para>
|
|
<literal>abbrev(inet '10.1.0.0/32')</literal>
|
|
<returnvalue>10.1.0.0</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>abbrev</function> ( <type>cidr</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Creates an abbreviated display format as text.
|
|
(The abbreviation consists of dropping all-zero octets to the right
|
|
of the netmask; more examples are in
|
|
<xref linkend="datatype-net-cidr-table"/>.)
|
|
</para>
|
|
<para>
|
|
<literal>abbrev(cidr '10.1.0.0/16')</literal>
|
|
<returnvalue>10.1/16</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>broadcast</primary>
|
|
</indexterm>
|
|
<function>broadcast</function> ( <type>inet</type> )
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the broadcast address for the address's network.
|
|
</para>
|
|
<para>
|
|
<literal>broadcast(inet '192.168.1.5/24')</literal>
|
|
<returnvalue>192.168.1.255/24</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>family</primary>
|
|
</indexterm>
|
|
<function>family</function> ( <type>inet</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the address's family: <literal>4</literal> for IPv4,
|
|
<literal>6</literal> for IPv6.
|
|
</para>
|
|
<para>
|
|
<literal>family(inet '::1')</literal>
|
|
<returnvalue>6</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>host</primary>
|
|
</indexterm>
|
|
<function>host</function> ( <type>inet</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the IP address as text, ignoring the netmask.
|
|
</para>
|
|
<para>
|
|
<literal>host(inet '192.168.1.0/24')</literal>
|
|
<returnvalue>192.168.1.0</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>hostmask</primary>
|
|
</indexterm>
|
|
<function>hostmask</function> ( <type>inet</type> )
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the host mask for the address's network.
|
|
</para>
|
|
<para>
|
|
<literal>hostmask(inet '192.168.23.20/30')</literal>
|
|
<returnvalue>0.0.0.3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>inet_merge</primary>
|
|
</indexterm>
|
|
<function>inet_merge</function> ( <type>inet</type>, <type>inet</type> )
|
|
<returnvalue>cidr</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the smallest network that includes both of the given networks.
|
|
</para>
|
|
<para>
|
|
<literal>inet_merge(inet '192.168.1.5/24', inet '192.168.2.5/24')</literal>
|
|
<returnvalue>192.168.0.0/22</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>inet_same_family</primary>
|
|
</indexterm>
|
|
<function>inet_same_family</function> ( <type>inet</type>, <type>inet</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tests whether the addresses belong to the same IP family.
|
|
</para>
|
|
<para>
|
|
<literal>inet_same_family(inet '192.168.1.5/24', inet '::1')</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>masklen</primary>
|
|
</indexterm>
|
|
<function>masklen</function> ( <type>inet</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the netmask length in bits.
|
|
</para>
|
|
<para>
|
|
<literal>masklen(inet '192.168.1.5/24')</literal>
|
|
<returnvalue>24</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>netmask</primary>
|
|
</indexterm>
|
|
<function>netmask</function> ( <type>inet</type> )
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the network mask for the address's network.
|
|
</para>
|
|
<para>
|
|
<literal>netmask(inet '192.168.1.5/24')</literal>
|
|
<returnvalue>255.255.255.0</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>network</primary>
|
|
</indexterm>
|
|
<function>network</function> ( <type>inet</type> )
|
|
<returnvalue>cidr</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the network part of the address, zeroing out
|
|
whatever is to the right of the netmask.
|
|
(This is equivalent to casting the value to <type>cidr</type>.)
|
|
</para>
|
|
<para>
|
|
<literal>network(inet '192.168.1.5/24')</literal>
|
|
<returnvalue>192.168.1.0/24</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>set_masklen</primary>
|
|
</indexterm>
|
|
<function>set_masklen</function> ( <type>inet</type>, <type>integer</type> )
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets the netmask length for an <type>inet</type> value.
|
|
The address part does not change.
|
|
</para>
|
|
<para>
|
|
<literal>set_masklen(inet '192.168.1.5/24', 16)</literal>
|
|
<returnvalue>192.168.1.5/16</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>set_masklen</function> ( <type>cidr</type>, <type>integer</type> )
|
|
<returnvalue>cidr</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets the netmask length for a <type>cidr</type> value.
|
|
Address bits to the right of the new netmask are set to zero.
|
|
</para>
|
|
<para>
|
|
<literal>set_masklen(cidr '192.168.1.0/24', 16)</literal>
|
|
<returnvalue>192.168.0.0/16</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>text</primary>
|
|
</indexterm>
|
|
<function>text</function> ( <type>inet</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the unabbreviated IP address and netmask length as text.
|
|
(This has the same result as an explicit cast to <type>text</type>.)
|
|
</para>
|
|
<para>
|
|
<literal>text(inet '192.168.1.5')</literal>
|
|
<returnvalue>192.168.1.5/32</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<tip>
|
|
<para>
|
|
The <function>abbrev</function>, <function>host</function>,
|
|
and <function>text</function> functions are primarily intended to offer
|
|
alternative display formats for IP addresses.
|
|
</para>
|
|
</tip>
|
|
|
|
<para>
|
|
The MAC address types, <type>macaddr</type> and <type>macaddr8</type>,
|
|
support the usual comparison operators shown in
|
|
<xref linkend="functions-comparison-op-table"/>
|
|
as well as the specialized functions shown in
|
|
<xref linkend="macaddr-functions-table"/>.
|
|
In addition, they support the bitwise logical operators
|
|
<literal>~</literal>, <literal>&</literal> and <literal>|</literal>
|
|
(NOT, AND and OR), just as shown above for IP addresses.
|
|
</para>
|
|
|
|
<table id="macaddr-functions-table">
|
|
<title>MAC Address Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>trunc</primary>
|
|
</indexterm>
|
|
<function>trunc</function> ( <type>macaddr</type> )
|
|
<returnvalue>macaddr</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets the last 3 bytes of the address to zero. The remaining prefix
|
|
can be associated with a particular manufacturer (using data not
|
|
included in <productname>PostgreSQL</productname>).
|
|
</para>
|
|
<para>
|
|
<literal>trunc(macaddr '12:34:56:78:90:ab')</literal>
|
|
<returnvalue>12:34:56:00:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>trunc</function> ( <type>macaddr8</type> )
|
|
<returnvalue>macaddr8</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets the last 5 bytes of the address to zero. The remaining prefix
|
|
can be associated with a particular manufacturer (using data not
|
|
included in <productname>PostgreSQL</productname>).
|
|
</para>
|
|
<para>
|
|
<literal>trunc(macaddr8 '12:34:56:78:90:ab:cd:ef')</literal>
|
|
<returnvalue>12:34:56:00:00:00:00:00</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>macaddr8_set7bit</primary>
|
|
</indexterm>
|
|
<function>macaddr8_set7bit</function> ( <type>macaddr8</type> )
|
|
<returnvalue>macaddr8</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets the 7th bit of the address to one, creating what is known as
|
|
modified EUI-64, for inclusion in an IPv6 address.
|
|
</para>
|
|
<para>
|
|
<literal>macaddr8_set7bit(macaddr8 '00:34:56:ab:cd:ef')</literal>
|
|
<returnvalue>02:34:56:ff:fe:ab:cd:ef</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-textsearch">
|
|
<title>Text Search Functions and Operators</title>
|
|
|
|
<indexterm zone="datatype-textsearch">
|
|
<primary>full text search</primary>
|
|
<secondary>functions and operators</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-textsearch">
|
|
<primary>text search</primary>
|
|
<secondary>functions and operators</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<xref linkend="textsearch-operators-table"/>,
|
|
<xref linkend="textsearch-functions-table"/> and
|
|
<xref linkend="textsearch-functions-debug-table"/>
|
|
summarize the functions and operators that are provided
|
|
for full text searching. See <xref linkend="textsearch"/> for a detailed
|
|
explanation of <productname>PostgreSQL</productname>'s text search
|
|
facility.
|
|
</para>
|
|
|
|
<table id="textsearch-operators-table">
|
|
<title>Text Search Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>tsvector</type> <literal>@@</literal> <type>tsquery</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>tsquery</type> <literal>@@</literal> <type>tsvector</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does <type>tsvector</type> match <type>tsquery</type>?
|
|
(The arguments can be given in either order.)
|
|
</para>
|
|
<para>
|
|
<literal>to_tsvector('fat cats ate rats') @@ to_tsquery('cat & rat')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>text</type> <literal>@@</literal> <type>tsquery</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does text string, after implicit invocation
|
|
of <function>to_tsvector()</function>, match <type>tsquery</type>?
|
|
</para>
|
|
<para>
|
|
<literal>'fat cats ate rats' @@ to_tsquery('cat & rat')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>tsvector</type> <literal>||</literal> <type>tsvector</type>
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates two <type>tsvector</type>s. If both inputs contain
|
|
lexeme positions, the second input's positions are adjusted
|
|
accordingly.
|
|
</para>
|
|
<para>
|
|
<literal>'a:1 b:2'::tsvector || 'c:1 d:2 b:3'::tsvector</literal>
|
|
<returnvalue>'a':1 'b':2,5 'c':3 'd':4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>tsquery</type> <literal>&&</literal> <type>tsquery</type>
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
ANDs two <type>tsquery</type>s together, producing a query that
|
|
matches documents that match both input queries.
|
|
</para>
|
|
<para>
|
|
<literal>'fat | rat'::tsquery && 'cat'::tsquery</literal>
|
|
<returnvalue>( 'fat' | 'rat' ) & 'cat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>tsquery</type> <literal>||</literal> <type>tsquery</type>
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
ORs two <type>tsquery</type>s together, producing a query that
|
|
matches documents that match either input query.
|
|
</para>
|
|
<para>
|
|
<literal>'fat | rat'::tsquery || 'cat'::tsquery</literal>
|
|
<returnvalue>'fat' | 'rat' | 'cat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>!!</literal> <type>tsquery</type>
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Negates a <type>tsquery</type>, producing a query that matches
|
|
documents that do not match the input query.
|
|
</para>
|
|
<para>
|
|
<literal>!! 'cat'::tsquery</literal>
|
|
<returnvalue>!'cat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>tsquery</type> <literal><-></literal> <type>tsquery</type>
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Constructs a phrase query, which matches if the two input queries
|
|
match at successive lexemes.
|
|
</para>
|
|
<para>
|
|
<literal>to_tsquery('fat') <-> to_tsquery('rat')</literal>
|
|
<returnvalue>'fat' <-> 'rat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>tsquery</type> <literal>@></literal> <type>tsquery</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does first <type>tsquery</type> contain the second? (This considers
|
|
only whether all the lexemes appearing in one query appear in the
|
|
other, ignoring the combining operators.)
|
|
</para>
|
|
<para>
|
|
<literal>'cat'::tsquery @> 'cat & rat'::tsquery</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>tsquery</type> <literal><@</literal> <type>tsquery</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is first <type>tsquery</type> contained in the second? (This
|
|
considers only whether all the lexemes appearing in one query appear
|
|
in the other, ignoring the combining operators.)
|
|
</para>
|
|
<para>
|
|
<literal>'cat'::tsquery <@ 'cat & rat'::tsquery</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>'cat'::tsquery <@ '!cat & rat'::tsquery</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
In addition to these specialized operators, the usual comparison
|
|
operators shown in <xref linkend="functions-comparison-op-table"/> are
|
|
available for types <type>tsvector</type> and <type>tsquery</type>.
|
|
These are not very
|
|
useful for text searching but allow, for example, unique indexes to be
|
|
built on columns of these types.
|
|
</para>
|
|
|
|
<table id="textsearch-functions-table">
|
|
<title>Text Search Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_to_tsvector</primary>
|
|
</indexterm>
|
|
<function>array_to_tsvector</function> ( <type>text[]</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts an array of text strings to a <type>tsvector</type>.
|
|
The given strings are used as lexemes as-is, without further
|
|
processing. Array elements must not be empty strings
|
|
or <literal>NULL</literal>.
|
|
</para>
|
|
<para>
|
|
<literal>array_to_tsvector('{fat,cat,rat}'::text[])</literal>
|
|
<returnvalue>'cat' 'fat' 'rat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>get_current_ts_config</primary>
|
|
</indexterm>
|
|
<function>get_current_ts_config</function> ( )
|
|
<returnvalue>regconfig</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the OID of the current default text search configuration
|
|
(as set by <xref linkend="guc-default-text-search-config"/>).
|
|
</para>
|
|
<para>
|
|
<literal>get_current_ts_config()</literal>
|
|
<returnvalue>english</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>length</primary>
|
|
</indexterm>
|
|
<function>length</function> ( <type>tsvector</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of lexemes in the <type>tsvector</type>.
|
|
</para>
|
|
<para>
|
|
<literal>length('fat:2,4 cat:3 rat:5A'::tsvector)</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>numnode</primary>
|
|
</indexterm>
|
|
<function>numnode</function> ( <type>tsquery</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of lexemes plus operators in
|
|
the <type>tsquery</type>.
|
|
</para>
|
|
<para>
|
|
<literal>numnode('(fat & rat) | cat'::tsquery)</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>plainto_tsquery</primary>
|
|
</indexterm>
|
|
<function>plainto_tsquery</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>query</parameter> <type>text</type> )
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts text to a <type>tsquery</type>, normalizing words according to
|
|
the specified or default configuration. Any punctuation in the string
|
|
is ignored (it does not determine query operators). The resulting
|
|
query matches documents containing all non-stopwords in the text.
|
|
</para>
|
|
<para>
|
|
<literal>plainto_tsquery('english', 'The Fat Rats')</literal>
|
|
<returnvalue>'fat' & 'rat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>phraseto_tsquery</primary>
|
|
</indexterm>
|
|
<function>phraseto_tsquery</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>query</parameter> <type>text</type> )
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts text to a <type>tsquery</type>, normalizing words according to
|
|
the specified or default configuration. Any punctuation in the string
|
|
is ignored (it does not determine query operators). The resulting
|
|
query matches phrases containing all non-stopwords in the text.
|
|
</para>
|
|
<para>
|
|
<literal>phraseto_tsquery('english', 'The Fat Rats')</literal>
|
|
<returnvalue>'fat' <-> 'rat'</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>phraseto_tsquery('english', 'The Cat and Rats')</literal>
|
|
<returnvalue>'cat' <2> 'rat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>websearch_to_tsquery</primary>
|
|
</indexterm>
|
|
<function>websearch_to_tsquery</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>query</parameter> <type>text</type> )
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts text to a <type>tsquery</type>, normalizing words according
|
|
to the specified or default configuration. Quoted word sequences are
|
|
converted to phrase tests. The word <quote>or</quote> is understood
|
|
as producing an OR operator, and a dash produces a NOT operator;
|
|
other punctuation is ignored.
|
|
This approximates the behavior of some common web search tools.
|
|
</para>
|
|
<para>
|
|
<literal>websearch_to_tsquery('english', '"fat rat" or cat dog')</literal>
|
|
<returnvalue>'fat' <-> 'rat' | 'cat' & 'dog'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>querytree</primary>
|
|
</indexterm>
|
|
<function>querytree</function> ( <type>tsquery</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Produces a representation of the indexable portion of
|
|
a <type>tsquery</type>. A result that is empty or
|
|
just <literal>T</literal> indicates a non-indexable query.
|
|
</para>
|
|
<para>
|
|
<literal>querytree('foo & ! bar'::tsquery)</literal>
|
|
<returnvalue>'foo'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>setweight</primary>
|
|
</indexterm>
|
|
<function>setweight</function> ( <parameter>vector</parameter> <type>tsvector</type>, <parameter>weight</parameter> <type>"char"</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Assigns the specified <parameter>weight</parameter> to each element
|
|
of the <parameter>vector</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>setweight('fat:2,4 cat:3 rat:5B'::tsvector, 'A')</literal>
|
|
<returnvalue>'cat':3A 'fat':2A,4A 'rat':5A</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>setweight</primary>
|
|
<secondary>setweight for specific lexeme(s)</secondary>
|
|
</indexterm>
|
|
<function>setweight</function> ( <parameter>vector</parameter> <type>tsvector</type>, <parameter>weight</parameter> <type>"char"</type>, <parameter>lexemes</parameter> <type>text[]</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Assigns the specified <parameter>weight</parameter> to elements
|
|
of the <parameter>vector</parameter> that are listed
|
|
in <parameter>lexemes</parameter>.
|
|
The strings in <parameter>lexemes</parameter> are taken as lexemes
|
|
as-is, without further processing. Strings that do not match any
|
|
lexeme in <parameter>vector</parameter> are ignored.
|
|
</para>
|
|
<para>
|
|
<literal>setweight('fat:2,4 cat:3 rat:5,6B'::tsvector, 'A', '{cat,rat}')</literal>
|
|
<returnvalue>'cat':3A 'fat':2,4 'rat':5A,6A</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>strip</primary>
|
|
</indexterm>
|
|
<function>strip</function> ( <type>tsvector</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes positions and weights from the <type>tsvector</type>.
|
|
</para>
|
|
<para>
|
|
<literal>strip('fat:2,4 cat:3 rat:5A'::tsvector)</literal>
|
|
<returnvalue>'cat' 'fat' 'rat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_tsquery</primary>
|
|
</indexterm>
|
|
<function>to_tsquery</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>query</parameter> <type>text</type> )
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts text to a <type>tsquery</type>, normalizing words according to
|
|
the specified or default configuration. The words must be combined
|
|
by valid <type>tsquery</type> operators.
|
|
</para>
|
|
<para>
|
|
<literal>to_tsquery('english', 'The & Fat & Rats')</literal>
|
|
<returnvalue>'fat' & 'rat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_tsvector</primary>
|
|
</indexterm>
|
|
<function>to_tsvector</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>document</parameter> <type>text</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts text to a <type>tsvector</type>, normalizing words according
|
|
to the specified or default configuration. Position information is
|
|
included in the result.
|
|
</para>
|
|
<para>
|
|
<literal>to_tsvector('english', 'The Fat Rats')</literal>
|
|
<returnvalue>'fat':2 'rat':3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>to_tsvector</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>document</parameter> <type>json</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>to_tsvector</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>document</parameter> <type>jsonb</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts each string value in the JSON document to
|
|
a <type>tsvector</type>, normalizing words according to the specified
|
|
or default configuration. The results are then concatenated in
|
|
document order to produce the output. Position information is
|
|
generated as though one stopword exists between each pair of string
|
|
values. (Beware that <quote>document order</quote> of the fields of a
|
|
JSON object is implementation-dependent when the input
|
|
is <type>jsonb</type>; observe the difference in the examples.)
|
|
</para>
|
|
<para>
|
|
<literal>to_tsvector('english', '{"aa": "The Fat Rats", "b": "dog"}'::json)</literal>
|
|
<returnvalue>'dog':5 'fat':2 'rat':3</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>to_tsvector('english', '{"aa": "The Fat Rats", "b": "dog"}'::jsonb)</literal>
|
|
<returnvalue>'dog':1 'fat':4 'rat':5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_to_tsvector</primary>
|
|
</indexterm>
|
|
<function>json_to_tsvector</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>document</parameter> <type>json</type>,
|
|
<parameter>filter</parameter> <type>jsonb</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_to_tsvector</primary>
|
|
</indexterm>
|
|
<function>jsonb_to_tsvector</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>document</parameter> <type>jsonb</type>,
|
|
<parameter>filter</parameter> <type>jsonb</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Selects each item in the JSON document that is requested by
|
|
the <parameter>filter</parameter> and converts each one to
|
|
a <type>tsvector</type>, normalizing words according to the specified
|
|
or default configuration. The results are then concatenated in
|
|
document order to produce the output. Position information is
|
|
generated as though one stopword exists between each pair of selected
|
|
items. (Beware that <quote>document order</quote> of the fields of a
|
|
JSON object is implementation-dependent when the input
|
|
is <type>jsonb</type>.)
|
|
The <parameter>filter</parameter> must be a <type>jsonb</type>
|
|
array containing zero or more of these keywords:
|
|
<literal>"string"</literal> (to include all string values),
|
|
<literal>"numeric"</literal> (to include all numeric values),
|
|
<literal>"boolean"</literal> (to include all boolean values),
|
|
<literal>"key"</literal> (to include all keys), or
|
|
<literal>"all"</literal> (to include all the above).
|
|
As a special case, the <parameter>filter</parameter> can also be a
|
|
simple JSON value that is one of these keywords.
|
|
</para>
|
|
<para>
|
|
<literal>json_to_tsvector('english', '{"a": "The Fat Rats", "b": 123}'::json, '["string", "numeric"]')</literal>
|
|
<returnvalue>'123':5 'fat':2 'rat':3</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>json_to_tsvector('english', '{"cat": "The Fat Rats", "dog": 123}'::json, '"all"')</literal>
|
|
<returnvalue>'123':9 'cat':1 'dog':7 'fat':4 'rat':5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_delete</primary>
|
|
</indexterm>
|
|
<function>ts_delete</function> ( <parameter>vector</parameter> <type>tsvector</type>, <parameter>lexeme</parameter> <type>text</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes any occurrence of the given <parameter>lexeme</parameter>
|
|
from the <parameter>vector</parameter>.
|
|
The <parameter>lexeme</parameter> string is treated as a lexeme as-is,
|
|
without further processing.
|
|
</para>
|
|
<para>
|
|
<literal>ts_delete('fat:2,4 cat:3 rat:5A'::tsvector, 'fat')</literal>
|
|
<returnvalue>'cat':3 'rat':5A</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>ts_delete</function> ( <parameter>vector</parameter> <type>tsvector</type>, <parameter>lexemes</parameter> <type>text[]</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes any occurrences of the lexemes
|
|
in <parameter>lexemes</parameter>
|
|
from the <parameter>vector</parameter>.
|
|
The strings in <parameter>lexemes</parameter> are taken as lexemes
|
|
as-is, without further processing. Strings that do not match any
|
|
lexeme in <parameter>vector</parameter> are ignored.
|
|
</para>
|
|
<para>
|
|
<literal>ts_delete('fat:2,4 cat:3 rat:5A'::tsvector, ARRAY['fat','rat'])</literal>
|
|
<returnvalue>'cat':3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_filter</primary>
|
|
</indexterm>
|
|
<function>ts_filter</function> ( <parameter>vector</parameter> <type>tsvector</type>, <parameter>weights</parameter> <type>"char"[]</type> )
|
|
<returnvalue>tsvector</returnvalue>
|
|
</para>
|
|
<para>
|
|
Selects only elements with the given <parameter>weights</parameter>
|
|
from the <parameter>vector</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>ts_filter('fat:2,4 cat:3b,7c rat:5A'::tsvector, '{a,b}')</literal>
|
|
<returnvalue>'cat':3B 'rat':5A</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_headline</primary>
|
|
</indexterm>
|
|
<function>ts_headline</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>document</parameter> <type>text</type>,
|
|
<parameter>query</parameter> <type>tsquery</type>
|
|
<optional>, <parameter>options</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Displays, in an abbreviated form, the match(es) for
|
|
the <parameter>query</parameter> in
|
|
the <parameter>document</parameter>, which must be raw text not
|
|
a <type>tsvector</type>. Words in the document are normalized
|
|
according to the specified or default configuration before matching to
|
|
the query. Use of this function is discussed in
|
|
<xref linkend="textsearch-headline"/>, which also describes the
|
|
available <parameter>options</parameter>.
|
|
</para>
|
|
<para>
|
|
<literal>ts_headline('The fat cat ate the rat.', 'cat')</literal>
|
|
<returnvalue>The fat <b>cat</b> ate the rat.</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>ts_headline</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>document</parameter> <type>json</type>,
|
|
<parameter>query</parameter> <type>tsquery</type>
|
|
<optional>, <parameter>options</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>ts_headline</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>document</parameter> <type>jsonb</type>,
|
|
<parameter>query</parameter> <type>tsquery</type>
|
|
<optional>, <parameter>options</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Displays, in an abbreviated form, match(es) for
|
|
the <parameter>query</parameter> that occur in string values
|
|
within the JSON <parameter>document</parameter>.
|
|
See <xref linkend="textsearch-headline"/> for more details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_headline('{"cat":"raining cats and dogs"}'::jsonb, 'cat')</literal>
|
|
<returnvalue>{"cat": "raining <b>cats</b> and dogs"}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_rank</primary>
|
|
</indexterm>
|
|
<function>ts_rank</function> (
|
|
<optional> <parameter>weights</parameter> <type>real[]</type>, </optional>
|
|
<parameter>vector</parameter> <type>tsvector</type>,
|
|
<parameter>query</parameter> <type>tsquery</type>
|
|
<optional>, <parameter>normalization</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>real</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes a score showing how well
|
|
the <parameter>vector</parameter> matches
|
|
the <parameter>query</parameter>. See
|
|
<xref linkend="textsearch-ranking"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_rank(to_tsvector('raining cats and dogs'), 'cat')</literal>
|
|
<returnvalue>0.06079271</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_rank_cd</primary>
|
|
</indexterm>
|
|
<function>ts_rank_cd</function> (
|
|
<optional> <parameter>weights</parameter> <type>real[]</type>, </optional>
|
|
<parameter>vector</parameter> <type>tsvector</type>,
|
|
<parameter>query</parameter> <type>tsquery</type>
|
|
<optional>, <parameter>normalization</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>real</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes a score showing how well
|
|
the <parameter>vector</parameter> matches
|
|
the <parameter>query</parameter>, using a cover density
|
|
algorithm. See <xref linkend="textsearch-ranking"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_rank_cd(to_tsvector('raining cats and dogs'), 'cat')</literal>
|
|
<returnvalue>0.1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_rewrite</primary>
|
|
</indexterm>
|
|
<function>ts_rewrite</function> ( <parameter>query</parameter> <type>tsquery</type>,
|
|
<parameter>target</parameter> <type>tsquery</type>,
|
|
<parameter>substitute</parameter> <type>tsquery</type> )
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces occurrences of <parameter>target</parameter>
|
|
with <parameter>substitute</parameter>
|
|
within the <parameter>query</parameter>.
|
|
See <xref linkend="textsearch-query-rewriting"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_rewrite('a & b'::tsquery, 'a'::tsquery, 'foo|bar'::tsquery)</literal>
|
|
<returnvalue>'b' & ( 'foo' | 'bar' )</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>ts_rewrite</function> ( <parameter>query</parameter> <type>tsquery</type>,
|
|
<parameter>select</parameter> <type>text</type> )
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces portions of the <parameter>query</parameter> according to
|
|
target(s) and substitute(s) obtained by executing
|
|
a <command>SELECT</command> command.
|
|
See <xref linkend="textsearch-query-rewriting"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>SELECT ts_rewrite('a & b'::tsquery, 'SELECT t,s FROM aliases')</literal>
|
|
<returnvalue>'b' & ( 'foo' | 'bar' )</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>tsquery_phrase</primary>
|
|
</indexterm>
|
|
<function>tsquery_phrase</function> ( <parameter>query1</parameter> <type>tsquery</type>, <parameter>query2</parameter> <type>tsquery</type> )
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Constructs a phrase query that searches
|
|
for matches of <parameter>query1</parameter>
|
|
and <parameter>query2</parameter> at successive lexemes (same
|
|
as <literal><-></literal> operator).
|
|
</para>
|
|
<para>
|
|
<literal>tsquery_phrase(to_tsquery('fat'), to_tsquery('cat'))</literal>
|
|
<returnvalue>'fat' <-> 'cat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>tsquery_phrase</function> ( <parameter>query1</parameter> <type>tsquery</type>, <parameter>query2</parameter> <type>tsquery</type>, <parameter>distance</parameter> <type>integer</type> )
|
|
<returnvalue>tsquery</returnvalue>
|
|
</para>
|
|
<para>
|
|
Constructs a phrase query that searches
|
|
for matches of <parameter>query1</parameter> and
|
|
<parameter>query2</parameter> that occur exactly
|
|
<parameter>distance</parameter> lexemes apart.
|
|
</para>
|
|
<para>
|
|
<literal>tsquery_phrase(to_tsquery('fat'), to_tsquery('cat'), 10)</literal>
|
|
<returnvalue>'fat' <10> 'cat'</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>tsvector_to_array</primary>
|
|
</indexterm>
|
|
<function>tsvector_to_array</function> ( <type>tsvector</type> )
|
|
<returnvalue>text[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts a <type>tsvector</type> to an array of lexemes.
|
|
</para>
|
|
<para>
|
|
<literal>tsvector_to_array('fat:2,4 cat:3 rat:5A'::tsvector)</literal>
|
|
<returnvalue>{cat,fat,rat}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>unnest</primary>
|
|
<secondary>for tsvector</secondary>
|
|
</indexterm>
|
|
<function>unnest</function> ( <type>tsvector</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>lexeme</parameter> <type>text</type>,
|
|
<parameter>positions</parameter> <type>smallint[]</type>,
|
|
<parameter>weights</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Expands a <type>tsvector</type> into a set of rows, one per lexeme.
|
|
</para>
|
|
<para>
|
|
<literal>select * from unnest('cat:3 fat:2,4 rat:5A'::tsvector)</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
lexeme | positions | weights
|
|
--------+-----------+---------
|
|
cat | {3} | {D}
|
|
fat | {2,4} | {D,D}
|
|
rat | {5} | {A}
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>
|
|
All the text search functions that accept an optional <type>regconfig</type>
|
|
argument will use the configuration specified by
|
|
<xref linkend="guc-default-text-search-config"/>
|
|
when that argument is omitted.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
The functions in
|
|
<xref linkend="textsearch-functions-debug-table"/>
|
|
are listed separately because they are not usually used in everyday text
|
|
searching operations. They are primarily helpful for development and
|
|
debugging of new text search configurations.
|
|
</para>
|
|
|
|
<table id="textsearch-functions-debug-table">
|
|
<title>Text Search Debugging Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_debug</primary>
|
|
</indexterm>
|
|
<function>ts_debug</function> (
|
|
<optional> <parameter>config</parameter> <type>regconfig</type>, </optional>
|
|
<parameter>document</parameter> <type>text</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>alias</parameter> <type>text</type>,
|
|
<parameter>description</parameter> <type>text</type>,
|
|
<parameter>token</parameter> <type>text</type>,
|
|
<parameter>dictionaries</parameter> <type>regdictionary[]</type>,
|
|
<parameter>dictionary</parameter> <type>regdictionary</type>,
|
|
<parameter>lexemes</parameter> <type>text[]</type> )
|
|
</para>
|
|
<para>
|
|
Extracts and normalizes tokens from
|
|
the <parameter>document</parameter> according to the specified or
|
|
default text search configuration, and returns information about how
|
|
each token was processed.
|
|
See <xref linkend="textsearch-configuration-testing"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_debug('english', 'The Brightest supernovaes')</literal>
|
|
<returnvalue>(asciiword,"Word, all ASCII",The,{english_stem},english_stem,{}) ...</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_lexize</primary>
|
|
</indexterm>
|
|
<function>ts_lexize</function> ( <parameter>dict</parameter> <type>regdictionary</type>, <parameter>token</parameter> <type>text</type> )
|
|
<returnvalue>text[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an array of replacement lexemes if the input token is known to
|
|
the dictionary, or an empty array if the token is known to the
|
|
dictionary but it is a stop word, or NULL if it is not a known word.
|
|
See <xref linkend="textsearch-dictionary-testing"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_lexize('english_stem', 'stars')</literal>
|
|
<returnvalue>{star}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_parse</primary>
|
|
</indexterm>
|
|
<function>ts_parse</function> ( <parameter>parser_name</parameter> <type>text</type>,
|
|
<parameter>document</parameter> <type>text</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>tokid</parameter> <type>integer</type>,
|
|
<parameter>token</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Extracts tokens from the <parameter>document</parameter> using the
|
|
named parser.
|
|
See <xref linkend="textsearch-parser-testing"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_parse('default', 'foo - bar')</literal>
|
|
<returnvalue>(1,foo) ...</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>ts_parse</function> ( <parameter>parser_oid</parameter> <type>oid</type>,
|
|
<parameter>document</parameter> <type>text</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>tokid</parameter> <type>integer</type>,
|
|
<parameter>token</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Extracts tokens from the <parameter>document</parameter> using a
|
|
parser specified by OID.
|
|
See <xref linkend="textsearch-parser-testing"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_parse(3722, 'foo - bar')</literal>
|
|
<returnvalue>(1,foo) ...</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_token_type</primary>
|
|
</indexterm>
|
|
<function>ts_token_type</function> ( <parameter>parser_name</parameter> <type>text</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>tokid</parameter> <type>integer</type>,
|
|
<parameter>alias</parameter> <type>text</type>,
|
|
<parameter>description</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Returns a table that describes each type of token the named parser can
|
|
recognize.
|
|
See <xref linkend="textsearch-parser-testing"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_token_type('default')</literal>
|
|
<returnvalue>(1,asciiword,"Word, all ASCII") ...</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>ts_token_type</function> ( <parameter>parser_oid</parameter> <type>oid</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>tokid</parameter> <type>integer</type>,
|
|
<parameter>alias</parameter> <type>text</type>,
|
|
<parameter>description</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Returns a table that describes each type of token a parser specified
|
|
by OID can recognize.
|
|
See <xref linkend="textsearch-parser-testing"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_token_type(3722)</literal>
|
|
<returnvalue>(1,asciiword,"Word, all ASCII") ...</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ts_stat</primary>
|
|
</indexterm>
|
|
<function>ts_stat</function> ( <parameter>sqlquery</parameter> <type>text</type>
|
|
<optional>, <parameter>weights</parameter> <type>text</type> </optional> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>word</parameter> <type>text</type>,
|
|
<parameter>ndoc</parameter> <type>integer</type>,
|
|
<parameter>nentry</parameter> <type>integer</type> )
|
|
</para>
|
|
<para>
|
|
Executes the <parameter>sqlquery</parameter>, which must return a
|
|
single <type>tsvector</type> column, and returns statistics about each
|
|
distinct lexeme contained in the data.
|
|
See <xref linkend="textsearch-statistics"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>ts_stat('SELECT vector FROM apod')</literal>
|
|
<returnvalue>(foo,10,15) ...</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="functions-uuid">
|
|
<title>UUID Functions</title>
|
|
|
|
<indexterm zone="datatype-uuid">
|
|
<primary>UUID</primary>
|
|
<secondary>generating</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>gen_random_uuid</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>uuid_extract_timestamp</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>uuid_extract_version</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> includes one function to generate a UUID:
|
|
<synopsis>
|
|
<function>gen_random_uuid</function> () <returnvalue>uuid</returnvalue>
|
|
</synopsis>
|
|
This function returns a version 4 (random) UUID. This is the most commonly
|
|
used type of UUID and is appropriate for most applications.
|
|
</para>
|
|
|
|
<para>
|
|
The <xref linkend="uuid-ossp"/> module provides additional functions that
|
|
implement other standard algorithms for generating UUIDs.
|
|
</para>
|
|
|
|
<para>
|
|
There are also functions to extract data from UUIDs:
|
|
<synopsis>
|
|
<function>uuid_extract_timestamp</function> (uuid) <returnvalue>timestamp with time zone</returnvalue>
|
|
</synopsis>
|
|
This function extracts a <type>timestamp with time zone</type> from UUID
|
|
version 1. For other versions, this function returns null. Note that the
|
|
extracted timestamp is not necessarily exactly equal to the time the UUID
|
|
was generated; this depends on the implementation that generated the UUID.
|
|
</para>
|
|
|
|
<para>
|
|
<synopsis>
|
|
<function>uuid_extract_version</function> (uuid) <returnvalue>smallint</returnvalue>
|
|
</synopsis>
|
|
This function extracts the version from a UUID of the variant described by
|
|
<ulink url="https://datatracker.ietf.org/doc/html/rfc4122">RFC 4122</ulink>. For
|
|
other variants, this function returns null. For example, for a UUID
|
|
generated by <function>gen_random_uuid</function>, this function will
|
|
return 4.
|
|
</para>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> also provides the usual comparison
|
|
operators shown in <xref linkend="functions-comparison-op-table"/> for
|
|
UUIDs.
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-xml">
|
|
|
|
<title>XML Functions</title>
|
|
|
|
<indexterm>
|
|
<primary>XML Functions</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The functions and function-like expressions described in this
|
|
section operate on values of type <type>xml</type>. See <xref
|
|
linkend="datatype-xml"/> for information about the <type>xml</type>
|
|
type. The function-like expressions <function>xmlparse</function>
|
|
and <function>xmlserialize</function> for converting to and from
|
|
type <type>xml</type> are documented there, not in this section.
|
|
</para>
|
|
|
|
<para>
|
|
Use of most of these functions
|
|
requires <productname>PostgreSQL</productname> to have been built
|
|
with <command>configure --with-libxml</command>.
|
|
</para>
|
|
|
|
<sect2 id="functions-producing-xml">
|
|
<title>Producing XML Content</title>
|
|
|
|
<para>
|
|
A set of functions and function-like expressions is available for
|
|
producing XML content from SQL data. As such, they are
|
|
particularly suitable for formatting query results into XML
|
|
documents for processing in client applications.
|
|
</para>
|
|
|
|
<sect3 id="functions-producing-xml-xmltext">
|
|
<title><literal>xmltext</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xmltext</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xmltext</function> ( <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The function <function>xmltext</function> returns an XML value with a single
|
|
text node containing the input argument as its content. Predefined entities
|
|
like ampersand (<literal><![CDATA[&]]></literal>), left and right angle brackets
|
|
(<literal><![CDATA[< >]]></literal>), and quotation marks (<literal><![CDATA[""]]></literal>)
|
|
are escaped.
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
SELECT xmltext('< foo & bar >');
|
|
xmltext
|
|
-------------------------
|
|
< foo & bar >
|
|
]]></screen>
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-producing-xml-xmlcomment">
|
|
<title><literal>xmlcomment</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xmlcomment</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xmlcomment</function> ( <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The function <function>xmlcomment</function> creates an XML value
|
|
containing an XML comment with the specified text as content.
|
|
The text cannot contain <quote><literal>--</literal></quote> or end with a
|
|
<quote><literal>-</literal></quote>, otherwise the resulting construct
|
|
would not be a valid XML comment.
|
|
If the argument is null, the result is null.
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
SELECT xmlcomment('hello');
|
|
|
|
xmlcomment
|
|
--------------
|
|
<!--hello-->
|
|
]]></screen>
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-producing-xml-xmlconcat">
|
|
<title><literal>xmlconcat</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xmlconcat</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xmlconcat</function> ( <type>xml</type> <optional>, ...</optional> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The function <function>xmlconcat</function> concatenates a list
|
|
of individual XML values to create a single value containing an
|
|
XML content fragment. Null values are omitted; the result is
|
|
only null if there are no nonnull arguments.
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
SELECT xmlconcat('<abc/>', '<bar>foo</bar>');
|
|
|
|
xmlconcat
|
|
----------------------
|
|
<abc/><bar>foo</bar>
|
|
]]></screen>
|
|
</para>
|
|
|
|
<para>
|
|
XML declarations, if present, are combined as follows. If all
|
|
argument values have the same XML version declaration, that
|
|
version is used in the result, else no version is used. If all
|
|
argument values have the standalone declaration value
|
|
<quote>yes</quote>, then that value is used in the result. If
|
|
all argument values have a standalone declaration value and at
|
|
least one is <quote>no</quote>, then that is used in the result.
|
|
Else the result will have no standalone declaration. If the
|
|
result is determined to require a standalone declaration but no
|
|
version declaration, a version declaration with version 1.0 will
|
|
be used because XML requires an XML declaration to contain a
|
|
version declaration. Encoding declarations are ignored and
|
|
removed in all cases.
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
SELECT xmlconcat('<?xml version="1.1"?><foo/>', '<?xml version="1.1" standalone="no"?><bar/>');
|
|
|
|
xmlconcat
|
|
-----------------------------------
|
|
<?xml version="1.1"?><foo/><bar/>
|
|
]]></screen>
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-producing-xml-xmlelement">
|
|
<title><literal>xmlelement</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xmlelement</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xmlelement</function> ( <literal>NAME</literal> <replaceable>name</replaceable> <optional>, <literal>XMLATTRIBUTES</literal> ( <replaceable>attvalue</replaceable> <optional> <literal>AS</literal> <replaceable>attname</replaceable> </optional> <optional>, ...</optional> ) </optional> <optional>, <replaceable>content</replaceable> <optional>, ...</optional></optional> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>xmlelement</function> expression produces an XML
|
|
element with the given name, attributes, and content.
|
|
The <replaceable>name</replaceable>
|
|
and <replaceable>attname</replaceable> items shown in the syntax are
|
|
simple identifiers, not values. The <replaceable>attvalue</replaceable>
|
|
and <replaceable>content</replaceable> items are expressions, which can
|
|
yield any <productname>PostgreSQL</productname> data type. The
|
|
argument(s) within <literal>XMLATTRIBUTES</literal> generate attributes
|
|
of the XML element; the <replaceable>content</replaceable> value(s) are
|
|
concatenated to form its content.
|
|
</para>
|
|
|
|
<para>
|
|
Examples:
|
|
<screen><![CDATA[
|
|
SELECT xmlelement(name foo);
|
|
|
|
xmlelement
|
|
------------
|
|
<foo/>
|
|
|
|
SELECT xmlelement(name foo, xmlattributes('xyz' as bar));
|
|
|
|
xmlelement
|
|
------------------
|
|
<foo bar="xyz"/>
|
|
|
|
SELECT xmlelement(name foo, xmlattributes(current_date as bar), 'cont', 'ent');
|
|
|
|
xmlelement
|
|
-------------------------------------
|
|
<foo bar="2007-01-26">content</foo>
|
|
]]></screen>
|
|
</para>
|
|
|
|
<para>
|
|
Element and attribute names that are not valid XML names are
|
|
escaped by replacing the offending characters by the sequence
|
|
<literal>_x<replaceable>HHHH</replaceable>_</literal>, where
|
|
<replaceable>HHHH</replaceable> is the character's Unicode
|
|
codepoint in hexadecimal notation. For example:
|
|
<screen><![CDATA[
|
|
SELECT xmlelement(name "foo$bar", xmlattributes('xyz' as "a&b"));
|
|
|
|
xmlelement
|
|
----------------------------------
|
|
<foo_x0024_bar a_x0026_b="xyz"/>
|
|
]]></screen>
|
|
</para>
|
|
|
|
<para>
|
|
An explicit attribute name need not be specified if the attribute
|
|
value is a column reference, in which case the column's name will
|
|
be used as the attribute name by default. In other cases, the
|
|
attribute must be given an explicit name. So this example is
|
|
valid:
|
|
<screen>
|
|
CREATE TABLE test (a xml, b xml);
|
|
SELECT xmlelement(name test, xmlattributes(a, b)) FROM test;
|
|
</screen>
|
|
But these are not:
|
|
<screen>
|
|
SELECT xmlelement(name test, xmlattributes('constant'), a, b) FROM test;
|
|
SELECT xmlelement(name test, xmlattributes(func(a, b))) FROM test;
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
Element content, if specified, will be formatted according to
|
|
its data type. If the content is itself of type <type>xml</type>,
|
|
complex XML documents can be constructed. For example:
|
|
<screen><![CDATA[
|
|
SELECT xmlelement(name foo, xmlattributes('xyz' as bar),
|
|
xmlelement(name abc),
|
|
xmlcomment('test'),
|
|
xmlelement(name xyz));
|
|
|
|
xmlelement
|
|
----------------------------------------------
|
|
<foo bar="xyz"><abc/><!--test--><xyz/></foo>
|
|
]]></screen>
|
|
|
|
Content of other types will be formatted into valid XML character
|
|
data. This means in particular that the characters <, >,
|
|
and & will be converted to entities. Binary data (data type
|
|
<type>bytea</type>) will be represented in base64 or hex
|
|
encoding, depending on the setting of the configuration parameter
|
|
<xref linkend="guc-xmlbinary"/>. The particular behavior for
|
|
individual data types is expected to evolve in order to align the
|
|
PostgreSQL mappings with those specified in SQL:2006 and later,
|
|
as discussed in <xref linkend="functions-xml-limits-casts"/>.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-producing-xml-xmlforest">
|
|
<title><literal>xmlforest</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xmlforest</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xmlforest</function> ( <replaceable>content</replaceable> <optional> <literal>AS</literal> <replaceable>name</replaceable> </optional> <optional>, ...</optional> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>xmlforest</function> expression produces an XML
|
|
forest (sequence) of elements using the given names and content.
|
|
As for <function>xmlelement</function>,
|
|
each <replaceable>name</replaceable> must be a simple identifier, while
|
|
the <replaceable>content</replaceable> expressions can have any data
|
|
type.
|
|
</para>
|
|
|
|
<para>
|
|
Examples:
|
|
<screen>
|
|
SELECT xmlforest('abc' AS foo, 123 AS bar);
|
|
|
|
xmlforest
|
|
------------------------------
|
|
<foo>abc</foo><bar>123</bar>
|
|
|
|
|
|
SELECT xmlforest(table_name, column_name)
|
|
FROM information_schema.columns
|
|
WHERE table_schema = 'pg_catalog';
|
|
|
|
xmlforest
|
|
------------------------------------&zwsp;-----------------------------------
|
|
<table_name>pg_authid</table_name>&zwsp;<column_name>rolname</column_name>
|
|
<table_name>pg_authid</table_name>&zwsp;<column_name>rolsuper</column_name>
|
|
...
|
|
</screen>
|
|
|
|
As seen in the second example, the element name can be omitted if
|
|
the content value is a column reference, in which case the column
|
|
name is used by default. Otherwise, a name must be specified.
|
|
</para>
|
|
|
|
<para>
|
|
Element names that are not valid XML names are escaped as shown
|
|
for <function>xmlelement</function> above. Similarly, content
|
|
data is escaped to make valid XML content, unless it is already
|
|
of type <type>xml</type>.
|
|
</para>
|
|
|
|
<para>
|
|
Note that XML forests are not valid XML documents if they consist
|
|
of more than one element, so it might be useful to wrap
|
|
<function>xmlforest</function> expressions in
|
|
<function>xmlelement</function>.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-producing-xml-xmlpi">
|
|
<title><literal>xmlpi</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xmlpi</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xmlpi</function> ( <literal>NAME</literal> <replaceable>name</replaceable> <optional>, <replaceable>content</replaceable> </optional> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>xmlpi</function> expression creates an XML
|
|
processing instruction.
|
|
As for <function>xmlelement</function>,
|
|
the <replaceable>name</replaceable> must be a simple identifier, while
|
|
the <replaceable>content</replaceable> expression can have any data type.
|
|
The <replaceable>content</replaceable>, if present, must not contain the
|
|
character sequence <literal>?></literal>.
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
SELECT xmlpi(name php, 'echo "hello world";');
|
|
|
|
xmlpi
|
|
-----------------------------
|
|
<?php echo "hello world";?>
|
|
]]></screen>
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-producing-xml-xmlroot">
|
|
<title><literal>xmlroot</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xmlroot</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xmlroot</function> ( <type>xml</type>, <literal>VERSION</literal> {<type>text</type>|<literal>NO VALUE</literal>} <optional>, <literal>STANDALONE</literal> {<literal>YES</literal>|<literal>NO</literal>|<literal>NO VALUE</literal>} </optional> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>xmlroot</function> expression alters the properties
|
|
of the root node of an XML value. If a version is specified,
|
|
it replaces the value in the root node's version declaration; if a
|
|
standalone setting is specified, it replaces the value in the
|
|
root node's standalone declaration.
|
|
</para>
|
|
|
|
<para>
|
|
<screen><![CDATA[
|
|
SELECT xmlroot(xmlparse(document '<?xml version="1.1"?><content>abc</content>'),
|
|
version '1.0', standalone yes);
|
|
|
|
xmlroot
|
|
----------------------------------------
|
|
<?xml version="1.0" standalone="yes"?>
|
|
<content>abc</content>
|
|
]]></screen>
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-xml-xmlagg">
|
|
<title><literal>xmlagg</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xmlagg</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xmlagg</function> ( <type>xml</type> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The function <function>xmlagg</function> is, unlike the other
|
|
functions described here, an aggregate function. It concatenates the
|
|
input values to the aggregate function call,
|
|
much like <function>xmlconcat</function> does, except that concatenation
|
|
occurs across rows rather than across expressions in a single row.
|
|
See <xref linkend="functions-aggregate"/> for additional information
|
|
about aggregate functions.
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
CREATE TABLE test (y int, x xml);
|
|
INSERT INTO test VALUES (1, '<foo>abc</foo>');
|
|
INSERT INTO test VALUES (2, '<bar/>');
|
|
SELECT xmlagg(x) FROM test;
|
|
xmlagg
|
|
----------------------
|
|
<foo>abc</foo><bar/>
|
|
]]></screen>
|
|
</para>
|
|
|
|
<para>
|
|
To determine the order of the concatenation, an <literal>ORDER BY</literal>
|
|
clause may be added to the aggregate call as described in
|
|
<xref linkend="syntax-aggregates"/>. For example:
|
|
|
|
<screen><![CDATA[
|
|
SELECT xmlagg(x ORDER BY y DESC) FROM test;
|
|
xmlagg
|
|
----------------------
|
|
<bar/><foo>abc</foo>
|
|
]]></screen>
|
|
</para>
|
|
|
|
<para>
|
|
The following non-standard approach used to be recommended
|
|
in previous versions, and may still be useful in specific
|
|
cases:
|
|
|
|
<screen><![CDATA[
|
|
SELECT xmlagg(x) FROM (SELECT * FROM test ORDER BY y DESC) AS tab;
|
|
xmlagg
|
|
----------------------
|
|
<bar/><foo>abc</foo>
|
|
]]></screen>
|
|
</para>
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-xml-predicates">
|
|
<title>XML Predicates</title>
|
|
|
|
<para>
|
|
The expressions described in this section check properties
|
|
of <type>xml</type> values.
|
|
</para>
|
|
|
|
<sect3 id="functions-producing-xml-is-document">
|
|
<title><literal>IS DOCUMENT</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>IS DOCUMENT</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<type>xml</type> <literal>IS DOCUMENT</literal> <returnvalue>boolean</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The expression <literal>IS DOCUMENT</literal> returns true if the
|
|
argument XML value is a proper XML document, false if it is not
|
|
(that is, it is a content fragment), or null if the argument is
|
|
null. See <xref linkend="datatype-xml"/> about the difference
|
|
between documents and content fragments.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-producing-xml-is-not-document">
|
|
<title><literal>IS NOT DOCUMENT</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>IS NOT DOCUMENT</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<type>xml</type> <literal>IS NOT DOCUMENT</literal> <returnvalue>boolean</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The expression <literal>IS NOT DOCUMENT</literal> returns false if the
|
|
argument XML value is a proper XML document, true if it is not (that is,
|
|
it is a content fragment), or null if the argument is null.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="xml-exists">
|
|
<title><literal>XMLEXISTS</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>XMLEXISTS</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>XMLEXISTS</function> ( <type>text</type> <literal>PASSING</literal> <optional><literal>BY</literal> {<literal>REF</literal>|<literal>VALUE</literal>}</optional> <type>xml</type> <optional><literal>BY</literal> {<literal>REF</literal>|<literal>VALUE</literal>}</optional> ) <returnvalue>boolean</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The function <function>xmlexists</function> evaluates an XPath 1.0
|
|
expression (the first argument), with the passed XML value as its context
|
|
item. The function returns false if the result of that evaluation
|
|
yields an empty node-set, true if it yields any other value. The
|
|
function returns null if any argument is null. A nonnull value
|
|
passed as the context item must be an XML document, not a content
|
|
fragment or any non-XML value.
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY VALUE '<towns><town>Toronto</town><town>Ottawa</town></towns>');
|
|
|
|
xmlexists
|
|
------------
|
|
t
|
|
(1 row)
|
|
]]></screen>
|
|
</para>
|
|
|
|
<para>
|
|
The <literal>BY REF</literal> and <literal>BY VALUE</literal> clauses
|
|
are accepted in <productname>PostgreSQL</productname>, but are ignored,
|
|
as discussed in <xref linkend="functions-xml-limits-postgresql"/>.
|
|
</para>
|
|
|
|
<para>
|
|
In the SQL standard, the <function>xmlexists</function> function
|
|
evaluates an expression in the XML Query language,
|
|
but <productname>PostgreSQL</productname> allows only an XPath 1.0
|
|
expression, as discussed in
|
|
<xref linkend="functions-xml-limits-xpath1"/>.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="xml-is-well-formed">
|
|
<title><literal>xml_is_well_formed</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xml_is_well_formed</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>xml_is_well_formed_document</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>xml_is_well_formed_content</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xml_is_well_formed</function> ( <type>text</type> ) <returnvalue>boolean</returnvalue>
|
|
<function>xml_is_well_formed_document</function> ( <type>text</type> ) <returnvalue>boolean</returnvalue>
|
|
<function>xml_is_well_formed_content</function> ( <type>text</type> ) <returnvalue>boolean</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
These functions check whether a <type>text</type> string represents
|
|
well-formed XML, returning a Boolean result.
|
|
<function>xml_is_well_formed_document</function> checks for a well-formed
|
|
document, while <function>xml_is_well_formed_content</function> checks
|
|
for well-formed content. <function>xml_is_well_formed</function> does
|
|
the former if the <xref linkend="guc-xmloption"/> configuration
|
|
parameter is set to <literal>DOCUMENT</literal>, or the latter if it is set to
|
|
<literal>CONTENT</literal>. This means that
|
|
<function>xml_is_well_formed</function> is useful for seeing whether
|
|
a simple cast to type <type>xml</type> will succeed, whereas the other two
|
|
functions are useful for seeing whether the corresponding variants of
|
|
<function>XMLPARSE</function> will succeed.
|
|
</para>
|
|
|
|
<para>
|
|
Examples:
|
|
|
|
<screen><![CDATA[
|
|
SET xmloption TO DOCUMENT;
|
|
SELECT xml_is_well_formed('<>');
|
|
xml_is_well_formed
|
|
--------------------
|
|
f
|
|
(1 row)
|
|
|
|
SELECT xml_is_well_formed('<abc/>');
|
|
xml_is_well_formed
|
|
--------------------
|
|
t
|
|
(1 row)
|
|
|
|
SET xmloption TO CONTENT;
|
|
SELECT xml_is_well_formed('abc');
|
|
xml_is_well_formed
|
|
--------------------
|
|
t
|
|
(1 row)
|
|
|
|
SELECT xml_is_well_formed_document('<pg:foo xmlns:pg="http://postgresql.org/stuff">bar</pg:foo>');
|
|
xml_is_well_formed_document
|
|
-----------------------------
|
|
t
|
|
(1 row)
|
|
|
|
SELECT xml_is_well_formed_document('<pg:foo xmlns:pg="http://postgresql.org/stuff">bar</my:foo>');
|
|
xml_is_well_formed_document
|
|
-----------------------------
|
|
f
|
|
(1 row)
|
|
]]></screen>
|
|
|
|
The last example shows that the checks include whether
|
|
namespaces are correctly matched.
|
|
</para>
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-xml-processing">
|
|
<title>Processing XML</title>
|
|
|
|
<para>
|
|
To process values of data type <type>xml</type>, PostgreSQL offers
|
|
the functions <function>xpath</function> and
|
|
<function>xpath_exists</function>, which evaluate XPath 1.0
|
|
expressions, and the <function>XMLTABLE</function>
|
|
table function.
|
|
</para>
|
|
|
|
<sect3 id="functions-xml-processing-xpath">
|
|
<title><literal>xpath</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>XPath</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xpath</function> ( <parameter>xpath</parameter> <type>text</type>, <parameter>xml</parameter> <type>xml</type> <optional>, <parameter>nsarray</parameter> <type>text[]</type> </optional> ) <returnvalue>xml[]</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The function <function>xpath</function> evaluates the XPath 1.0
|
|
expression <parameter>xpath</parameter> (given as text)
|
|
against the XML value
|
|
<parameter>xml</parameter>. It returns an array of XML values
|
|
corresponding to the node-set produced by the XPath expression.
|
|
If the XPath expression returns a scalar value rather than a node-set,
|
|
a single-element array is returned.
|
|
</para>
|
|
|
|
<para>
|
|
The second argument must be a well formed XML document. In particular,
|
|
it must have a single root node element.
|
|
</para>
|
|
|
|
<para>
|
|
The optional third argument of the function is an array of namespace
|
|
mappings. This array should be a two-dimensional <type>text</type> array with
|
|
the length of the second axis being equal to 2 (i.e., it should be an
|
|
array of arrays, each of which consists of exactly 2 elements).
|
|
The first element of each array entry is the namespace name (alias), the
|
|
second the namespace URI. It is not required that aliases provided in
|
|
this array be the same as those being used in the XML document itself (in
|
|
other words, both in the XML document and in the <function>xpath</function>
|
|
function context, aliases are <emphasis>local</emphasis>).
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
SELECT xpath('/my:a/text()', '<my:a xmlns:my="http://example.com">test</my:a>',
|
|
ARRAY[ARRAY['my', 'http://example.com']]);
|
|
|
|
xpath
|
|
--------
|
|
{test}
|
|
(1 row)
|
|
]]></screen>
|
|
</para>
|
|
|
|
<para>
|
|
To deal with default (anonymous) namespaces, do something like this:
|
|
<screen><![CDATA[
|
|
SELECT xpath('//mydefns:b/text()', '<a xmlns="http://example.com"><b>test</b></a>',
|
|
ARRAY[ARRAY['mydefns', 'http://example.com']]);
|
|
|
|
xpath
|
|
--------
|
|
{test}
|
|
(1 row)
|
|
]]></screen>
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-xml-processing-xpath-exists">
|
|
<title><literal>xpath_exists</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xpath_exists</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>xpath_exists</function> ( <parameter>xpath</parameter> <type>text</type>, <parameter>xml</parameter> <type>xml</type> <optional>, <parameter>nsarray</parameter> <type>text[]</type> </optional> ) <returnvalue>boolean</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The function <function>xpath_exists</function> is a specialized form
|
|
of the <function>xpath</function> function. Instead of returning the
|
|
individual XML values that satisfy the XPath 1.0 expression, this function
|
|
returns a Boolean indicating whether the query was satisfied or not
|
|
(specifically, whether it produced any value other than an empty node-set).
|
|
This function is equivalent to the <literal>XMLEXISTS</literal> predicate,
|
|
except that it also offers support for a namespace mapping argument.
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
SELECT xpath_exists('/my:a/text()', '<my:a xmlns:my="http://example.com">test</my:a>',
|
|
ARRAY[ARRAY['my', 'http://example.com']]);
|
|
|
|
xpath_exists
|
|
--------------
|
|
t
|
|
(1 row)
|
|
]]></screen>
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-xml-processing-xmltable">
|
|
<title><literal>xmltable</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>xmltable</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="functions-xml-processing-xmltable">
|
|
<primary>table function</primary>
|
|
<secondary>XMLTABLE</secondary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>XMLTABLE</function> (
|
|
<optional> <literal>XMLNAMESPACES</literal> ( <replaceable>namespace_uri</replaceable> <literal>AS</literal> <replaceable>namespace_name</replaceable> <optional>, ...</optional> ), </optional>
|
|
<replaceable>row_expression</replaceable> <literal>PASSING</literal> <optional><literal>BY</literal> {<literal>REF</literal>|<literal>VALUE</literal>}</optional> <replaceable>document_expression</replaceable> <optional><literal>BY</literal> {<literal>REF</literal>|<literal>VALUE</literal>}</optional>
|
|
<literal>COLUMNS</literal> <replaceable>name</replaceable> { <replaceable>type</replaceable> <optional><literal>PATH</literal> <replaceable>column_expression</replaceable></optional> <optional><literal>DEFAULT</literal> <replaceable>default_expression</replaceable></optional> <optional><literal>NOT NULL</literal> | <literal>NULL</literal></optional>
|
|
| <literal>FOR ORDINALITY</literal> }
|
|
<optional>, ...</optional>
|
|
) <returnvalue>setof record</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>xmltable</function> expression produces a table based
|
|
on an XML value, an XPath filter to extract rows, and a
|
|
set of column definitions.
|
|
Although it syntactically resembles a function, it can only appear
|
|
as a table in a query's <literal>FROM</literal> clause.
|
|
</para>
|
|
|
|
<para>
|
|
The optional <literal>XMLNAMESPACES</literal> clause gives a
|
|
comma-separated list of namespace definitions, where
|
|
each <replaceable>namespace_uri</replaceable> is a <type>text</type>
|
|
expression and each <replaceable>namespace_name</replaceable> is a simple
|
|
identifier. It specifies the XML namespaces used in the document and
|
|
their aliases. A default namespace specification is not currently
|
|
supported.
|
|
</para>
|
|
|
|
<para>
|
|
The required <replaceable>row_expression</replaceable> argument is an
|
|
XPath 1.0 expression (given as <type>text</type>) that is evaluated,
|
|
passing the XML value <replaceable>document_expression</replaceable> as
|
|
its context item, to obtain a set of XML nodes. These nodes are what
|
|
<function>xmltable</function> transforms into output rows. No rows
|
|
will be produced if the <replaceable>document_expression</replaceable>
|
|
is null, nor if the <replaceable>row_expression</replaceable> produces
|
|
an empty node-set or any value other than a node-set.
|
|
</para>
|
|
|
|
<para>
|
|
<replaceable>document_expression</replaceable> provides the context
|
|
item for the <replaceable>row_expression</replaceable>. It must be a
|
|
well-formed XML document; fragments/forests are not accepted.
|
|
The <literal>BY REF</literal> and <literal>BY VALUE</literal> clauses
|
|
are accepted but ignored, as discussed in
|
|
<xref linkend="functions-xml-limits-postgresql"/>.
|
|
</para>
|
|
|
|
<para>
|
|
In the SQL standard, the <function>xmltable</function> function
|
|
evaluates expressions in the XML Query language,
|
|
but <productname>PostgreSQL</productname> allows only XPath 1.0
|
|
expressions, as discussed in
|
|
<xref linkend="functions-xml-limits-xpath1"/>.
|
|
</para>
|
|
|
|
<para>
|
|
The required <literal>COLUMNS</literal> clause specifies the
|
|
column(s) that will be produced in the output table.
|
|
See the syntax summary above for the format.
|
|
A name is required for each column, as is a data type
|
|
(unless <literal>FOR ORDINALITY</literal> is specified, in which case
|
|
type <type>integer</type> is implicit). The path, default and
|
|
nullability clauses are optional.
|
|
</para>
|
|
|
|
<para>
|
|
A column marked <literal>FOR ORDINALITY</literal> will be populated
|
|
with row numbers, starting with 1, in the order of nodes retrieved from
|
|
the <replaceable>row_expression</replaceable>'s result node-set.
|
|
At most one column may be marked <literal>FOR ORDINALITY</literal>.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
XPath 1.0 does not specify an order for nodes in a node-set, so code
|
|
that relies on a particular order of the results will be
|
|
implementation-dependent. Details can be found in
|
|
<xref linkend="xml-xpath-1-specifics"/>.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
The <replaceable>column_expression</replaceable> for a column is an
|
|
XPath 1.0 expression that is evaluated for each row, with the current
|
|
node from the <replaceable>row_expression</replaceable> result as its
|
|
context item, to find the value of the column. If
|
|
no <replaceable>column_expression</replaceable> is given, then the
|
|
column name is used as an implicit path.
|
|
</para>
|
|
|
|
<para>
|
|
If a column's XPath expression returns a non-XML value (which is limited
|
|
to string, boolean, or double in XPath 1.0) and the column has a
|
|
PostgreSQL type other than <type>xml</type>, the column will be set
|
|
as if by assigning the value's string representation to the PostgreSQL
|
|
type. (If the value is a boolean, its string representation is taken
|
|
to be <literal>1</literal> or <literal>0</literal> if the output
|
|
column's type category is numeric, otherwise <literal>true</literal> or
|
|
<literal>false</literal>.)
|
|
</para>
|
|
|
|
<para>
|
|
If a column's XPath expression returns a non-empty set of XML nodes
|
|
and the column's PostgreSQL type is <type>xml</type>, the column will
|
|
be assigned the expression result exactly, if it is of document or
|
|
content form.
|
|
<footnote>
|
|
<para>
|
|
A result containing more than one element node at the top level, or
|
|
non-whitespace text outside of an element, is an example of content form.
|
|
An XPath result can be of neither form, for example if it returns an
|
|
attribute node selected from the element that contains it. Such a result
|
|
will be put into content form with each such disallowed node replaced by
|
|
its string value, as defined for the XPath 1.0
|
|
<function>string</function> function.
|
|
</para>
|
|
</footnote>
|
|
</para>
|
|
|
|
<para>
|
|
A non-XML result assigned to an <type>xml</type> output column produces
|
|
content, a single text node with the string value of the result.
|
|
An XML result assigned to a column of any other type may not have more than
|
|
one node, or an error is raised. If there is exactly one node, the column
|
|
will be set as if by assigning the node's string
|
|
value (as defined for the XPath 1.0 <function>string</function> function)
|
|
to the PostgreSQL type.
|
|
</para>
|
|
|
|
<para>
|
|
The string value of an XML element is the concatenation, in document order,
|
|
of all text nodes contained in that element and its descendants. The string
|
|
value of an element with no descendant text nodes is an
|
|
empty string (not <literal>NULL</literal>).
|
|
Any <literal>xsi:nil</literal> attributes are ignored.
|
|
Note that the whitespace-only <literal>text()</literal> node between two non-text
|
|
elements is preserved, and that leading whitespace on a <literal>text()</literal>
|
|
node is not flattened.
|
|
The XPath 1.0 <function>string</function> function may be consulted for the
|
|
rules defining the string value of other XML node types and non-XML values.
|
|
</para>
|
|
|
|
<para>
|
|
The conversion rules presented here are not exactly those of the SQL
|
|
standard, as discussed in <xref linkend="functions-xml-limits-casts"/>.
|
|
</para>
|
|
|
|
<para>
|
|
If the path expression returns an empty node-set
|
|
(typically, when it does not match)
|
|
for a given row, the column will be set to <literal>NULL</literal>, unless
|
|
a <replaceable>default_expression</replaceable> is specified; then the
|
|
value resulting from evaluating that expression is used.
|
|
</para>
|
|
|
|
<para>
|
|
A <replaceable>default_expression</replaceable>, rather than being
|
|
evaluated immediately when <function>xmltable</function> is called,
|
|
is evaluated each time a default is needed for the column.
|
|
If the expression qualifies as stable or immutable, the repeat
|
|
evaluation may be skipped.
|
|
This means that you can usefully use volatile functions like
|
|
<function>nextval</function> in
|
|
<replaceable>default_expression</replaceable>.
|
|
</para>
|
|
|
|
<para>
|
|
Columns may be marked <literal>NOT NULL</literal>. If the
|
|
<replaceable>column_expression</replaceable> for a <literal>NOT
|
|
NULL</literal> column does not match anything and there is
|
|
no <literal>DEFAULT</literal> or
|
|
the <replaceable>default_expression</replaceable> also evaluates to null,
|
|
an error is reported.
|
|
</para>
|
|
|
|
<para>
|
|
Examples:
|
|
<screen><![CDATA[
|
|
CREATE TABLE xmldata AS SELECT
|
|
xml $$
|
|
<ROWS>
|
|
<ROW id="1">
|
|
<COUNTRY_ID>AU</COUNTRY_ID>
|
|
<COUNTRY_NAME>Australia</COUNTRY_NAME>
|
|
</ROW>
|
|
<ROW id="5">
|
|
<COUNTRY_ID>JP</COUNTRY_ID>
|
|
<COUNTRY_NAME>Japan</COUNTRY_NAME>
|
|
<PREMIER_NAME>Shinzo Abe</PREMIER_NAME>
|
|
<SIZE unit="sq_mi">145935</SIZE>
|
|
</ROW>
|
|
<ROW id="6">
|
|
<COUNTRY_ID>SG</COUNTRY_ID>
|
|
<COUNTRY_NAME>Singapore</COUNTRY_NAME>
|
|
<SIZE unit="sq_km">697</SIZE>
|
|
</ROW>
|
|
</ROWS>
|
|
$$ AS data;
|
|
|
|
SELECT xmltable.*
|
|
FROM xmldata,
|
|
XMLTABLE('//ROWS/ROW'
|
|
PASSING data
|
|
COLUMNS id int PATH '@id',
|
|
ordinality FOR ORDINALITY,
|
|
"COUNTRY_NAME" text,
|
|
country_id text PATH 'COUNTRY_ID',
|
|
size_sq_km float PATH 'SIZE[@unit = "sq_km"]',
|
|
size_other text PATH
|
|
'concat(SIZE[@unit!="sq_km"], " ", SIZE[@unit!="sq_km"]/@unit)',
|
|
premier_name text PATH 'PREMIER_NAME' DEFAULT 'not specified');
|
|
|
|
id | ordinality | COUNTRY_NAME | country_id | size_sq_km | size_other | premier_name
|
|
----+------------+--------------+------------+------------+--------------+---------------
|
|
1 | 1 | Australia | AU | | | not specified
|
|
5 | 2 | Japan | JP | | 145935 sq_mi | Shinzo Abe
|
|
6 | 3 | Singapore | SG | 697 | | not specified
|
|
]]></screen>
|
|
|
|
The following example shows concatenation of multiple text() nodes,
|
|
usage of the column name as XPath filter, and the treatment of whitespace,
|
|
XML comments and processing instructions:
|
|
|
|
<screen><![CDATA[
|
|
CREATE TABLE xmlelements AS SELECT
|
|
xml $$
|
|
<root>
|
|
<element> Hello<!-- xyxxz -->2a2<?aaaaa?> <!--x--> bbb<x>xxx</x>CC </element>
|
|
</root>
|
|
$$ AS data;
|
|
|
|
SELECT xmltable.*
|
|
FROM xmlelements, XMLTABLE('/root' PASSING data COLUMNS element text);
|
|
element
|
|
-------------------------
|
|
Hello2a2 bbbxxxCC
|
|
]]></screen>
|
|
</para>
|
|
|
|
<para>
|
|
The following example illustrates how
|
|
the <literal>XMLNAMESPACES</literal> clause can be used to specify
|
|
a list of namespaces
|
|
used in the XML document as well as in the XPath expressions:
|
|
|
|
<screen><![CDATA[
|
|
WITH xmldata(data) AS (VALUES ('
|
|
<example xmlns="http://example.com/myns" xmlns:B="http://example.com/b">
|
|
<item foo="1" B:bar="2"/>
|
|
<item foo="3" B:bar="4"/>
|
|
<item foo="4" B:bar="5"/>
|
|
</example>'::xml)
|
|
)
|
|
SELECT xmltable.*
|
|
FROM XMLTABLE(XMLNAMESPACES('http://example.com/myns' AS x,
|
|
'http://example.com/b' AS "B"),
|
|
'/x:example/x:item'
|
|
PASSING (SELECT data FROM xmldata)
|
|
COLUMNS foo int PATH '@foo',
|
|
bar int PATH '@B:bar');
|
|
foo | bar
|
|
-----+-----
|
|
1 | 2
|
|
3 | 4
|
|
4 | 5
|
|
(3 rows)
|
|
]]></screen>
|
|
</para>
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-xml-mapping">
|
|
<title>Mapping Tables to XML</title>
|
|
|
|
<indexterm zone="functions-xml-mapping">
|
|
<primary>XML export</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The following functions map the contents of relational tables to
|
|
XML values. They can be thought of as XML export functionality:
|
|
<synopsis>
|
|
<function>table_to_xml</function> ( <parameter>table</parameter> <type>regclass</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
<function>query_to_xml</function> ( <parameter>query</parameter> <type>text</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
<function>cursor_to_xml</function> ( <parameter>cursor</parameter> <type>refcursor</type>, <parameter>count</parameter> <type>integer</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
</para>
|
|
|
|
<para>
|
|
<function>table_to_xml</function> maps the content of the named
|
|
table, passed as parameter <parameter>table</parameter>. The
|
|
<type>regclass</type> type accepts strings identifying tables using the
|
|
usual notation, including optional schema qualification and
|
|
double quotes (see <xref linkend="datatype-oid"/> for details).
|
|
<function>query_to_xml</function> executes the
|
|
query whose text is passed as parameter
|
|
<parameter>query</parameter> and maps the result set.
|
|
<function>cursor_to_xml</function> fetches the indicated number of
|
|
rows from the cursor specified by the parameter
|
|
<parameter>cursor</parameter>. This variant is recommended if
|
|
large tables have to be mapped, because the result value is built
|
|
up in memory by each function.
|
|
</para>
|
|
|
|
<para>
|
|
If <parameter>tableforest</parameter> is false, then the resulting
|
|
XML document looks like this:
|
|
<screen><![CDATA[
|
|
<tablename>
|
|
<row>
|
|
<columnname1>data</columnname1>
|
|
<columnname2>data</columnname2>
|
|
</row>
|
|
|
|
<row>
|
|
...
|
|
</row>
|
|
|
|
...
|
|
</tablename>
|
|
]]></screen>
|
|
|
|
If <parameter>tableforest</parameter> is true, the result is an
|
|
XML content fragment that looks like this:
|
|
<screen><![CDATA[
|
|
<tablename>
|
|
<columnname1>data</columnname1>
|
|
<columnname2>data</columnname2>
|
|
</tablename>
|
|
|
|
<tablename>
|
|
...
|
|
</tablename>
|
|
|
|
...
|
|
]]></screen>
|
|
|
|
If no table name is available, that is, when mapping a query or a
|
|
cursor, the string <literal>table</literal> is used in the first
|
|
format, <literal>row</literal> in the second format.
|
|
</para>
|
|
|
|
<para>
|
|
The choice between these formats is up to the user. The first
|
|
format is a proper XML document, which will be important in many
|
|
applications. The second format tends to be more useful in the
|
|
<function>cursor_to_xml</function> function if the result values are to be
|
|
reassembled into one document later on. The functions for
|
|
producing XML content discussed above, in particular
|
|
<function>xmlelement</function>, can be used to alter the results
|
|
to taste.
|
|
</para>
|
|
|
|
<para>
|
|
The data values are mapped in the same way as described for the
|
|
function <function>xmlelement</function> above.
|
|
</para>
|
|
|
|
<para>
|
|
The parameter <parameter>nulls</parameter> determines whether null
|
|
values should be included in the output. If true, null values in
|
|
columns are represented as:
|
|
<screen><![CDATA[
|
|
<columnname xsi:nil="true"/>
|
|
]]></screen>
|
|
where <literal>xsi</literal> is the XML namespace prefix for XML
|
|
Schema Instance. An appropriate namespace declaration will be
|
|
added to the result value. If false, columns containing null
|
|
values are simply omitted from the output.
|
|
</para>
|
|
|
|
<para>
|
|
The parameter <parameter>targetns</parameter> specifies the
|
|
desired XML namespace of the result. If no particular namespace
|
|
is wanted, an empty string should be passed.
|
|
</para>
|
|
|
|
<para>
|
|
The following functions return XML Schema documents describing the
|
|
mappings performed by the corresponding functions above:
|
|
<synopsis>
|
|
<function>table_to_xmlschema</function> ( <parameter>table</parameter> <type>regclass</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
<function>query_to_xmlschema</function> ( <parameter>query</parameter> <type>text</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
<function>cursor_to_xmlschema</function> ( <parameter>cursor</parameter> <type>refcursor</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
It is essential that the same parameters are passed in order to
|
|
obtain matching XML data mappings and XML Schema documents.
|
|
</para>
|
|
|
|
<para>
|
|
The following functions produce XML data mappings and the
|
|
corresponding XML Schema in one document (or forest), linked
|
|
together. They can be useful where self-contained and
|
|
self-describing results are wanted:
|
|
<synopsis>
|
|
<function>table_to_xml_and_xmlschema</function> ( <parameter>table</parameter> <type>regclass</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
<function>query_to_xml_and_xmlschema</function> ( <parameter>query</parameter> <type>text</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
</para>
|
|
|
|
<para>
|
|
In addition, the following functions are available to produce
|
|
analogous mappings of entire schemas or the entire current
|
|
database:
|
|
<synopsis>
|
|
<function>schema_to_xml</function> ( <parameter>schema</parameter> <type>name</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
<function>schema_to_xmlschema</function> ( <parameter>schema</parameter> <type>name</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
<function>schema_to_xml_and_xmlschema</function> ( <parameter>schema</parameter> <type>name</type>, <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
|
|
<function>database_to_xml</function> ( <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
<function>database_to_xmlschema</function> ( <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
<function>database_to_xml_and_xmlschema</function> ( <parameter>nulls</parameter> <type>boolean</type>,
|
|
<parameter>tableforest</parameter> <type>boolean</type>, <parameter>targetns</parameter> <type>text</type> ) <returnvalue>xml</returnvalue>
|
|
</synopsis>
|
|
|
|
These functions ignore tables that are not readable by the current user.
|
|
The database-wide functions additionally ignore schemas that the current
|
|
user does not have <literal>USAGE</literal> (lookup) privilege for.
|
|
</para>
|
|
|
|
<para>
|
|
Note that these potentially produce a lot of data, which needs to
|
|
be built up in memory. When requesting content mappings of large
|
|
schemas or databases, it might be worthwhile to consider mapping the
|
|
tables separately instead, possibly even through a cursor.
|
|
</para>
|
|
|
|
<para>
|
|
The result of a schema content mapping looks like this:
|
|
|
|
<screen><![CDATA[
|
|
<schemaname>
|
|
|
|
table1-mapping
|
|
|
|
table2-mapping
|
|
|
|
...
|
|
|
|
</schemaname>]]></screen>
|
|
|
|
where the format of a table mapping depends on the
|
|
<parameter>tableforest</parameter> parameter as explained above.
|
|
</para>
|
|
|
|
<para>
|
|
The result of a database content mapping looks like this:
|
|
|
|
<screen><![CDATA[
|
|
<dbname>
|
|
|
|
<schema1name>
|
|
...
|
|
</schema1name>
|
|
|
|
<schema2name>
|
|
...
|
|
</schema2name>
|
|
|
|
...
|
|
|
|
</dbname>]]></screen>
|
|
|
|
where the schema mapping is as above.
|
|
</para>
|
|
|
|
<para>
|
|
As an example of using the output produced by these functions,
|
|
<xref linkend="xslt-xml-html"/> shows an XSLT stylesheet that
|
|
converts the output of
|
|
<function>table_to_xml_and_xmlschema</function> to an HTML
|
|
document containing a tabular rendition of the table data. In a
|
|
similar manner, the results from these functions can be
|
|
converted into other XML-based formats.
|
|
</para>
|
|
|
|
<example id="xslt-xml-html">
|
|
<title>XSLT Stylesheet for Converting SQL/XML Output to HTML</title>
|
|
<programlisting><![CDATA[
|
|
<?xml version="1.0"?>
|
|
<xsl:stylesheet version="1.0"
|
|
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
|
|
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
|
|
xmlns="http://www.w3.org/1999/xhtml"
|
|
>
|
|
|
|
<xsl:output method="xml"
|
|
doctype-system="http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"
|
|
doctype-public="-//W3C/DTD XHTML 1.0 Strict//EN"
|
|
indent="yes"/>
|
|
|
|
<xsl:template match="/*">
|
|
<xsl:variable name="schema" select="//xsd:schema"/>
|
|
<xsl:variable name="tabletypename"
|
|
select="$schema/xsd:element[@name=name(current())]/@type"/>
|
|
<xsl:variable name="rowtypename"
|
|
select="$schema/xsd:complexType[@name=$tabletypename]/xsd:sequence/xsd:element[@name='row']/@type"/>
|
|
|
|
<html>
|
|
<head>
|
|
<title><xsl:value-of select="name(current())"/></title>
|
|
</head>
|
|
<body>
|
|
<table>
|
|
<tr>
|
|
<xsl:for-each select="$schema/xsd:complexType[@name=$rowtypename]/xsd:sequence/xsd:element/@name">
|
|
<th><xsl:value-of select="."/></th>
|
|
</xsl:for-each>
|
|
</tr>
|
|
|
|
<xsl:for-each select="row">
|
|
<tr>
|
|
<xsl:for-each select="*">
|
|
<td><xsl:value-of select="."/></td>
|
|
</xsl:for-each>
|
|
</tr>
|
|
</xsl:for-each>
|
|
</table>
|
|
</body>
|
|
</html>
|
|
</xsl:template>
|
|
|
|
</xsl:stylesheet>
|
|
]]></programlisting>
|
|
</example>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-json">
|
|
<title>JSON Functions and Operators</title>
|
|
|
|
<indexterm zone="functions-json">
|
|
<primary>JSON</primary>
|
|
<secondary>functions and operators</secondary>
|
|
</indexterm>
|
|
<indexterm zone="functions-json">
|
|
<primary>SQL/JSON</primary>
|
|
<secondary>functions and expressions</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
This section describes:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
functions and operators for processing and creating JSON data
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
the SQL/JSON path language
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
the SQL/JSON query functions
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
To provide native support for JSON data types within the SQL environment,
|
|
<productname>PostgreSQL</productname> implements the
|
|
<firstterm>SQL/JSON data model</firstterm>.
|
|
This model comprises sequences of items. Each item can hold SQL scalar
|
|
values, with an additional SQL/JSON null value, and composite data structures
|
|
that use JSON arrays and objects. The model is a formalization of the implied
|
|
data model in the JSON specification
|
|
<ulink url="https://datatracker.ietf.org/doc/html/rfc7159">RFC 7159</ulink>.
|
|
</para>
|
|
|
|
<para>
|
|
SQL/JSON allows you to handle JSON data alongside regular SQL data,
|
|
with transaction support, including:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
Uploading JSON data into the database and storing it in
|
|
regular SQL columns as character or binary strings.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Generating JSON objects and arrays from relational data.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Querying JSON data using SQL/JSON query functions and
|
|
SQL/JSON path language expressions.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
To learn more about the SQL/JSON standard, see
|
|
<xref linkend="sqltr-19075-6"/>. For details on JSON types
|
|
supported in <productname>PostgreSQL</productname>,
|
|
see <xref linkend="datatype-json"/>.
|
|
</para>
|
|
|
|
<sect2 id="functions-json-processing">
|
|
<title>Processing and Creating JSON Data</title>
|
|
|
|
<para>
|
|
<xref linkend="functions-json-op-table"/> shows the operators that
|
|
are available for use with JSON data types (see <xref
|
|
linkend="datatype-json"/>).
|
|
In addition, the usual comparison operators shown in <xref
|
|
linkend="functions-comparison-op-table"/> are available for
|
|
<type>jsonb</type>, though not for <type>json</type>. The comparison
|
|
operators follow the ordering rules for B-tree operations outlined in
|
|
<xref linkend="json-indexing"/>.
|
|
See also <xref linkend="functions-aggregate"/> for the aggregate
|
|
function <function>json_agg</function> which aggregates record
|
|
values as JSON, the aggregate function
|
|
<function>json_object_agg</function> which aggregates pairs of values
|
|
into a JSON object, and their <type>jsonb</type> equivalents,
|
|
<function>jsonb_agg</function> and <function>jsonb_object_agg</function>.
|
|
</para>
|
|
|
|
<table id="functions-json-op-table">
|
|
<title><type>json</type> and <type>jsonb</type> Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>json</type> <literal>-></literal> <type>integer</type>
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>jsonb</type> <literal>-></literal> <type>integer</type>
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts <parameter>n</parameter>'th element of JSON array
|
|
(array elements are indexed from zero, but negative integers count
|
|
from the end).
|
|
</para>
|
|
<para>
|
|
<literal>'[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -> 2</literal>
|
|
<returnvalue>{"c":"baz"}</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>'[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -> -3</literal>
|
|
<returnvalue>{"a":"foo"}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>json</type> <literal>-></literal> <type>text</type>
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>jsonb</type> <literal>-></literal> <type>text</type>
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts JSON object field with the given key.
|
|
</para>
|
|
<para>
|
|
<literal>'{"a": {"b":"foo"}}'::json -> 'a'</literal>
|
|
<returnvalue>{"b":"foo"}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>json</type> <literal>->></literal> <type>integer</type>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>jsonb</type> <literal>->></literal> <type>integer</type>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts <parameter>n</parameter>'th element of JSON array,
|
|
as <type>text</type>.
|
|
</para>
|
|
<para>
|
|
<literal>'[1,2,3]'::json ->> 2</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>json</type> <literal>->></literal> <type>text</type>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>jsonb</type> <literal>->></literal> <type>text</type>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts JSON object field with the given key, as <type>text</type>.
|
|
</para>
|
|
<para>
|
|
<literal>'{"a":1,"b":2}'::json ->> 'b'</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>json</type> <literal>#></literal> <type>text[]</type>
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>jsonb</type> <literal>#></literal> <type>text[]</type>
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts JSON sub-object at the specified path, where path elements
|
|
can be either field keys or array indexes.
|
|
</para>
|
|
<para>
|
|
<literal>'{"a": {"b": ["foo","bar"]}}'::json #> '{a,b,1}'</literal>
|
|
<returnvalue>"bar"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>json</type> <literal>#>></literal> <type>text[]</type>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<type>jsonb</type> <literal>#>></literal> <type>text[]</type>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts JSON sub-object at the specified path as <type>text</type>.
|
|
</para>
|
|
<para>
|
|
<literal>'{"a": {"b": ["foo","bar"]}}'::json #>> '{a,b,1}'</literal>
|
|
<returnvalue>bar</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>
|
|
The field/element/path extraction operators return NULL, rather than
|
|
failing, if the JSON input does not have the right structure to match
|
|
the request; for example if no such key or array element exists.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
Some further operators exist only for <type>jsonb</type>, as shown
|
|
in <xref linkend="functions-jsonb-op-table"/>.
|
|
<xref linkend="json-indexing"/>
|
|
describes how these operators can be used to effectively search indexed
|
|
<type>jsonb</type> data.
|
|
</para>
|
|
|
|
<table id="functions-jsonb-op-table">
|
|
<title>Additional <type>jsonb</type> Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>@></literal> <type>jsonb</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the first JSON value contain the second?
|
|
(See <xref linkend="json-containment"/> for details about containment.)
|
|
</para>
|
|
<para>
|
|
<literal>'{"a":1, "b":2}'::jsonb @> '{"b":2}'::jsonb</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal><@</literal> <type>jsonb</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the first JSON value contained in the second?
|
|
</para>
|
|
<para>
|
|
<literal>'{"b":2}'::jsonb <@ '{"a":1, "b":2}'::jsonb</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>?</literal> <type>text</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the text string exist as a top-level key or array element within
|
|
the JSON value?
|
|
</para>
|
|
<para>
|
|
<literal>'{"a":1, "b":2}'::jsonb ? 'b'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>'["a", "b", "c"]'::jsonb ? 'b'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>?|</literal> <type>text[]</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Do any of the strings in the text array exist as top-level keys or
|
|
array elements?
|
|
</para>
|
|
<para>
|
|
<literal>'{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'd']</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>?&</literal> <type>text[]</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Do all of the strings in the text array exist as top-level keys or
|
|
array elements?
|
|
</para>
|
|
<para>
|
|
<literal>'["a", "b", "c"]'::jsonb ?& array['a', 'b']</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>||</literal> <type>jsonb</type>
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates two <type>jsonb</type> values.
|
|
Concatenating two arrays generates an array containing all the
|
|
elements of each input. Concatenating two objects generates an
|
|
object containing the union of their
|
|
keys, taking the second object's value when there are duplicate keys.
|
|
All other cases are treated by converting a non-array input into a
|
|
single-element array, and then proceeding as for two arrays.
|
|
Does not operate recursively: only the top-level array or object
|
|
structure is merged.
|
|
</para>
|
|
<para>
|
|
<literal>'["a", "b"]'::jsonb || '["a", "d"]'::jsonb</literal>
|
|
<returnvalue>["a", "b", "a", "d"]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>'{"a": "b"}'::jsonb || '{"c": "d"}'::jsonb</literal>
|
|
<returnvalue>{"a": "b", "c": "d"}</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>'[1, 2]'::jsonb || '3'::jsonb</literal>
|
|
<returnvalue>[1, 2, 3]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>'{"a": "b"}'::jsonb || '42'::jsonb</literal>
|
|
<returnvalue>[{"a": "b"}, 42]</returnvalue>
|
|
</para>
|
|
<para>
|
|
To append an array to another array as a single entry, wrap it
|
|
in an additional layer of array, for example:
|
|
</para>
|
|
<para>
|
|
<literal>'[1, 2]'::jsonb || jsonb_build_array('[3, 4]'::jsonb)</literal>
|
|
<returnvalue>[1, 2, [3, 4]]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>-</literal> <type>text</type>
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Deletes a key (and its value) from a JSON object, or matching string
|
|
value(s) from a JSON array.
|
|
</para>
|
|
<para>
|
|
<literal>'{"a": "b", "c": "d"}'::jsonb - 'a'</literal>
|
|
<returnvalue>{"c": "d"}</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>'["a", "b", "c", "b"]'::jsonb - 'b'</literal>
|
|
<returnvalue>["a", "c"]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>-</literal> <type>text[]</type>
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Deletes all matching keys or array elements from the left operand.
|
|
</para>
|
|
<para>
|
|
<literal>'{"a": "b", "c": "d"}'::jsonb - '{a,c}'::text[]</literal>
|
|
<returnvalue>{}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>-</literal> <type>integer</type>
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Deletes the array element with specified index (negative
|
|
integers count from the end). Throws an error if JSON value
|
|
is not an array.
|
|
</para>
|
|
<para>
|
|
<literal>'["a", "b"]'::jsonb - 1 </literal>
|
|
<returnvalue>["a"]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>#-</literal> <type>text[]</type>
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Deletes the field or array element at the specified path, where path
|
|
elements can be either field keys or array indexes.
|
|
</para>
|
|
<para>
|
|
<literal>'["a", {"b":1}]'::jsonb #- '{1,b}'</literal>
|
|
<returnvalue>["a", {}]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>@?</literal> <type>jsonpath</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does JSON path return any item for the specified JSON value?
|
|
(This is useful only with SQL-standard JSON path expressions, not
|
|
<link linkend="functions-sqljson-check-expressions">predicate check
|
|
expressions</link>, since those always return a value.)
|
|
</para>
|
|
<para>
|
|
<literal>'{"a":[1,2,3,4,5]}'::jsonb @? '$.a[*] ? (@ > 2)'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>jsonb</type> <literal>@@</literal> <type>jsonpath</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the result of a JSON path predicate check for the
|
|
specified JSON value.
|
|
(This is useful only
|
|
with <link linkend="functions-sqljson-check-expressions">predicate
|
|
check expressions</link>, not SQL-standard JSON path expressions,
|
|
since it will return <literal>NULL</literal> if the path result is
|
|
not a single boolean value.)
|
|
</para>
|
|
<para>
|
|
<literal>'{"a":[1,2,3,4,5]}'::jsonb @@ '$.a[*] > 2'</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>
|
|
The <type>jsonpath</type> operators <literal>@?</literal>
|
|
and <literal>@@</literal> suppress the following errors: missing object
|
|
field or array element, unexpected JSON item type, datetime and numeric
|
|
errors. The <type>jsonpath</type>-related functions described below can
|
|
also be told to suppress these types of errors. This behavior might be
|
|
helpful when searching JSON document collections of varying structure.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
<xref linkend="functions-json-creation-table"/> shows the functions that are
|
|
available for constructing <type>json</type> and <type>jsonb</type> values.
|
|
Some functions in this table have a <literal>RETURNING</literal> clause,
|
|
which specifies the data type returned. It must be one of <type>json</type>,
|
|
<type>jsonb</type>, <type>bytea</type>, a character string type (<type>text</type>,
|
|
<type>char</type>, <type>varchar</type>, or <type>nchar</type>), or a type
|
|
for which there is a cast from <type>json</type> to that type.
|
|
By default, the <type>json</type> type is returned.
|
|
</para>
|
|
|
|
<table id="functions-json-creation-table">
|
|
<title>JSON Creation Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_json</primary>
|
|
</indexterm>
|
|
<function>to_json</function> ( <type>anyelement</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_jsonb</primary>
|
|
</indexterm>
|
|
<function>to_jsonb</function> ( <type>anyelement</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts any SQL value to <type>json</type> or <type>jsonb</type>.
|
|
Arrays and composites are converted recursively to arrays and
|
|
objects (multidimensional arrays become arrays of arrays in JSON).
|
|
Otherwise, if there is a cast from the SQL data type
|
|
to <type>json</type>, the cast function will be used to perform the
|
|
conversion;<footnote>
|
|
<para>
|
|
For example, the <xref linkend="hstore"/> extension has a cast
|
|
from <type>hstore</type> to <type>json</type>, so that
|
|
<type>hstore</type> values converted via the JSON creation functions
|
|
will be represented as JSON objects, not as primitive string values.
|
|
</para>
|
|
</footnote>
|
|
otherwise, a scalar JSON value is produced. For any scalar other than
|
|
a number, a Boolean, or a null value, the text representation will be
|
|
used, with escaping as necessary to make it a valid JSON string value.
|
|
</para>
|
|
<para>
|
|
<literal>to_json('Fred said "Hi."'::text)</literal>
|
|
<returnvalue>"Fred said \"Hi.\""</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>to_jsonb(row(42, 'Fred said "Hi."'::text))</literal>
|
|
<returnvalue>{"f1": 42, "f2": "Fred said \"Hi.\""}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_to_json</primary>
|
|
</indexterm>
|
|
<function>array_to_json</function> ( <type>anyarray</type> <optional>, <type>boolean</type> </optional> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts an SQL array to a JSON array. The behavior is the same
|
|
as <function>to_json</function> except that line feeds will be added
|
|
between top-level array elements if the optional boolean parameter is
|
|
true.
|
|
</para>
|
|
<para>
|
|
<literal>array_to_json('{{1,5},{99,100}}'::int[])</literal>
|
|
<returnvalue>[[1,5],[99,100]]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<!--
|
|
Note that this is barely legible in the output; it looks like a
|
|
salad of braces and brackets. It would be better to split it out
|
|
in multiple lines, but that's surprisingly hard to do in a way that
|
|
matches in HTML and PDF output. Other standard SQL/JSON functions
|
|
have the same problem.
|
|
-->
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm><primary>json_array</primary></indexterm>
|
|
<function>json_array</function> (
|
|
<optional> { <replaceable>value_expression</replaceable> <optional> <literal>FORMAT JSON</literal> </optional> } <optional>, ...</optional> </optional>
|
|
<optional> { <literal>NULL</literal> | <literal>ABSENT</literal> } <literal>ON NULL</literal> </optional>
|
|
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>json_array</function> (
|
|
<optional> <replaceable>query_expression</replaceable> </optional>
|
|
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
|
|
</para>
|
|
<para>
|
|
Constructs a JSON array from either a series of
|
|
<replaceable>value_expression</replaceable> parameters or from the results
|
|
of <replaceable>query_expression</replaceable>,
|
|
which must be a SELECT query returning a single column. If
|
|
<literal>ABSENT ON NULL</literal> is specified, NULL values are ignored.
|
|
This is always the case if a
|
|
<replaceable>query_expression</replaceable> is used.
|
|
</para>
|
|
<para>
|
|
<literal>json_array(1,true,json '{"a":null}')</literal>
|
|
<returnvalue>[1, true, {"a":null}]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>json_array(SELECT * FROM (VALUES(1),(2)) t)</literal>
|
|
<returnvalue>[1, 2]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>row_to_json</primary>
|
|
</indexterm>
|
|
<function>row_to_json</function> ( <type>record</type> <optional>, <type>boolean</type> </optional> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts an SQL composite value to a JSON object. The behavior is the
|
|
same as <function>to_json</function> except that line feeds will be
|
|
added between top-level elements if the optional boolean parameter is
|
|
true.
|
|
</para>
|
|
<para>
|
|
<literal>row_to_json(row(1,'foo'))</literal>
|
|
<returnvalue>{"f1":1,"f2":"foo"}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_build_array</primary>
|
|
</indexterm>
|
|
<function>json_build_array</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_build_array</primary>
|
|
</indexterm>
|
|
<function>jsonb_build_array</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Builds a possibly-heterogeneously-typed JSON array out of a variadic
|
|
argument list. Each argument is converted as
|
|
per <function>to_json</function> or <function>to_jsonb</function>.
|
|
</para>
|
|
<para>
|
|
<literal>json_build_array(1, 2, 'foo', 4, 5)</literal>
|
|
<returnvalue>[1, 2, "foo", 4, 5]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_build_object</primary>
|
|
</indexterm>
|
|
<function>json_build_object</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_build_object</primary>
|
|
</indexterm>
|
|
<function>jsonb_build_object</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Builds a JSON object out of a variadic argument list. By convention,
|
|
the argument list consists of alternating keys and values. Key
|
|
arguments are coerced to text; value arguments are converted as
|
|
per <function>to_json</function> or <function>to_jsonb</function>.
|
|
</para>
|
|
<para>
|
|
<literal>json_build_object('foo', 1, 2, row(3,'bar'))</literal>
|
|
<returnvalue>{"foo" : 1, "2" : {"f1":3,"f2":"bar"}}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm><primary>json_object</primary></indexterm>
|
|
<function>json_object</function> (
|
|
<optional> { <replaceable>key_expression</replaceable> { <literal>VALUE</literal> | ':' }
|
|
<replaceable>value_expression</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> }<optional>, ...</optional> </optional>
|
|
<optional> { <literal>NULL</literal> | <literal>ABSENT</literal> } <literal>ON NULL</literal> </optional>
|
|
<optional> { <literal>WITH</literal> | <literal>WITHOUT</literal> } <literal>UNIQUE</literal> <optional> <literal>KEYS</literal> </optional> </optional>
|
|
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
|
|
</para>
|
|
<para>
|
|
Constructs a JSON object of all the key/value pairs given,
|
|
or an empty object if none are given.
|
|
<replaceable>key_expression</replaceable> is a scalar expression
|
|
defining the <acronym>JSON</acronym> key, which is
|
|
converted to the <type>text</type> type.
|
|
It cannot be <literal>NULL</literal> nor can it
|
|
belong to a type that has a cast to the <type>json</type> type.
|
|
If <literal>WITH UNIQUE KEYS</literal> is specified, there must not
|
|
be any duplicate <replaceable>key_expression</replaceable>.
|
|
Any pair for which the <replaceable>value_expression</replaceable>
|
|
evaluates to <literal>NULL</literal> is omitted from the output
|
|
if <literal>ABSENT ON NULL</literal> is specified;
|
|
if <literal>NULL ON NULL</literal> is specified or the clause
|
|
omitted, the key is included with value <literal>NULL</literal>.
|
|
</para>
|
|
<para>
|
|
<literal>json_object('code' VALUE 'P123', 'title': 'Jaws')</literal>
|
|
<returnvalue>{"code" : "P123", "title" : "Jaws"}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_object</primary>
|
|
</indexterm>
|
|
<function>json_object</function> ( <type>text[]</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_object</primary>
|
|
</indexterm>
|
|
<function>jsonb_object</function> ( <type>text[]</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Builds a JSON object out of a text array. The array must have either
|
|
exactly one dimension with an even number of members, in which case
|
|
they are taken as alternating key/value pairs, or two dimensions
|
|
such that each inner array has exactly two elements, which
|
|
are taken as a key/value pair. All values are converted to JSON
|
|
strings.
|
|
</para>
|
|
<para>
|
|
<literal>json_object('{a, 1, b, "def", c, 3.5}')</literal>
|
|
<returnvalue>{"a" : "1", "b" : "def", "c" : "3.5"}</returnvalue>
|
|
</para>
|
|
<para><literal>json_object('{{a, 1}, {b, "def"}, {c, 3.5}}')</literal>
|
|
<returnvalue>{"a" : "1", "b" : "def", "c" : "3.5"}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>json_object</function> ( <parameter>keys</parameter> <type>text[]</type>, <parameter>values</parameter> <type>text[]</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>jsonb_object</function> ( <parameter>keys</parameter> <type>text[]</type>, <parameter>values</parameter> <type>text[]</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
This form of <function>json_object</function> takes keys and values
|
|
pairwise from separate text arrays. Otherwise it is identical to
|
|
the one-argument form.
|
|
</para>
|
|
<para>
|
|
<literal>json_object('{a,b}', '{1,2}')</literal>
|
|
<returnvalue>{"a": "1", "b": "2"}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry">
|
|
<para role="func_signature">
|
|
<indexterm><primary>json constructor</primary></indexterm>
|
|
<function>json</function> (
|
|
<replaceable>expression</replaceable>
|
|
<optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional></optional>
|
|
<optional> { <literal>WITH</literal> | <literal>WITHOUT</literal> } <literal>UNIQUE</literal> <optional> <literal>KEYS</literal> </optional></optional> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts a given expression specified as <type>text</type> or
|
|
<type>bytea</type> string (in UTF8 encoding) into a JSON
|
|
value. If <replaceable>expression</replaceable> is NULL, an
|
|
<acronym>SQL</acronym> null value is returned.
|
|
If <literal>WITH UNIQUE</literal> is specified, the
|
|
<replaceable>expression</replaceable> must not contain any duplicate
|
|
object keys.
|
|
</para>
|
|
<para>
|
|
<literal>json('{"a":123, "b":[true,"foo"], "a":"bar"}')</literal>
|
|
<returnvalue>{"a":123, "b":[true,"foo"], "a":"bar"}</returnvalue>
|
|
</para>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry">
|
|
<para role="func_signature">
|
|
<indexterm><primary>json_scalar</primary></indexterm>
|
|
<function>json_scalar</function> ( <replaceable>expression</replaceable> )
|
|
</para>
|
|
<para>
|
|
Converts a given SQL scalar value into a JSON scalar value.
|
|
If the input is NULL, an <acronym>SQL</acronym> null is returned. If
|
|
the input is number or a boolean value, a corresponding JSON number
|
|
or boolean value is returned. For any other value, a JSON string is
|
|
returned.
|
|
</para>
|
|
<para>
|
|
<literal>json_scalar(123.45)</literal>
|
|
<returnvalue>123.45</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>json_scalar(CURRENT_TIMESTAMP)</literal>
|
|
<returnvalue>"2022-05-10T10:51:04.62128-04:00"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry">
|
|
<para role="func_signature">
|
|
<function>json_serialize</function> (
|
|
<replaceable>expression</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional>
|
|
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional> )
|
|
</para>
|
|
<para>
|
|
Converts an SQL/JSON expression into a character or binary string. The
|
|
<replaceable>expression</replaceable> can be of any JSON type, any
|
|
character string type, or <type>bytea</type> in UTF8 encoding.
|
|
The returned type used in <literal> RETURNING</literal> can be any
|
|
character string type or <type>bytea</type>. The default is
|
|
<type>text</type>.
|
|
</para>
|
|
<para>
|
|
<literal>json_serialize('{ "a" : 1 } ' RETURNING bytea)</literal>
|
|
<returnvalue>\x7b20226122203a2031207d20</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-sqljson-misc" /> details SQL/JSON
|
|
facilities for testing JSON.
|
|
</para>
|
|
|
|
<table id="functions-sqljson-misc">
|
|
<title>SQL/JSON Testing Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function signature
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm><primary>IS JSON</primary></indexterm>
|
|
<replaceable>expression</replaceable> <literal>IS</literal> <optional> <literal>NOT</literal> </optional> <literal>JSON</literal>
|
|
<optional> { <literal>VALUE</literal> | <literal>SCALAR</literal> | <literal>ARRAY</literal> | <literal>OBJECT</literal> } </optional>
|
|
<optional> { <literal>WITH</literal> | <literal>WITHOUT</literal> } <literal>UNIQUE</literal> <optional> <literal>KEYS</literal> </optional> </optional>
|
|
</para>
|
|
<para>
|
|
This predicate tests whether <replaceable>expression</replaceable> can be
|
|
parsed as JSON, possibly of a specified type.
|
|
If <literal>SCALAR</literal> or <literal>ARRAY</literal> or
|
|
<literal>OBJECT</literal> is specified, the
|
|
test is whether or not the JSON is of that particular type. If
|
|
<literal>WITH UNIQUE KEYS</literal> is specified, then any object in the
|
|
<replaceable>expression</replaceable> is also tested to see if it
|
|
has duplicate keys.
|
|
</para>
|
|
<para>
|
|
<programlisting>
|
|
SELECT js,
|
|
js IS JSON "json?",
|
|
js IS JSON SCALAR "scalar?",
|
|
js IS JSON OBJECT "object?",
|
|
js IS JSON ARRAY "array?"
|
|
FROM (VALUES
|
|
('123'), ('"abc"'), ('{"a": "b"}'), ('[1,2]'),('abc')) foo(js);
|
|
js | json? | scalar? | object? | array?
|
|
------------+-------+---------+---------+--------
|
|
123 | t | t | f | f
|
|
"abc" | t | t | f | f
|
|
{"a": "b"} | t | f | t | f
|
|
[1,2] | t | f | f | t
|
|
abc | f | f | f | f
|
|
</programlisting>
|
|
</para>
|
|
<para>
|
|
<programlisting>
|
|
SELECT js,
|
|
js IS JSON OBJECT "object?",
|
|
js IS JSON ARRAY "array?",
|
|
js IS JSON ARRAY WITH UNIQUE KEYS "array w. UK?",
|
|
js IS JSON ARRAY WITHOUT UNIQUE KEYS "array w/o UK?"
|
|
FROM (VALUES ('[{"a":"1"},
|
|
{"b":"2","b":"3"}]')) foo(js);
|
|
-[ RECORD 1 ]-+--------------------
|
|
js | [{"a":"1"}, +
|
|
| {"b":"2","b":"3"}]
|
|
object? | f
|
|
array? | t
|
|
array w. UK? | f
|
|
array w/o UK? | t
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-json-processing-table"/> shows the functions that
|
|
are available for processing <type>json</type> and <type>jsonb</type> values.
|
|
</para>
|
|
|
|
<table id="functions-json-processing-table">
|
|
<title>JSON Processing Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_array_elements</primary>
|
|
</indexterm>
|
|
<function>json_array_elements</function> ( <type>json</type> )
|
|
<returnvalue>setof json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_array_elements</primary>
|
|
</indexterm>
|
|
<function>jsonb_array_elements</function> ( <type>jsonb</type> )
|
|
<returnvalue>setof jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Expands the top-level JSON array into a set of JSON values.
|
|
</para>
|
|
<para>
|
|
<literal>select * from json_array_elements('[1,true, [2,false]]')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
value
|
|
-----------
|
|
1
|
|
true
|
|
[2,false]
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_array_elements_text</primary>
|
|
</indexterm>
|
|
<function>json_array_elements_text</function> ( <type>json</type> )
|
|
<returnvalue>setof text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_array_elements_text</primary>
|
|
</indexterm>
|
|
<function>jsonb_array_elements_text</function> ( <type>jsonb</type> )
|
|
<returnvalue>setof text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Expands the top-level JSON array into a set of <type>text</type> values.
|
|
</para>
|
|
<para>
|
|
<literal>select * from json_array_elements_text('["foo", "bar"]')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
value
|
|
-----------
|
|
foo
|
|
bar
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_array_length</primary>
|
|
</indexterm>
|
|
<function>json_array_length</function> ( <type>json</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_array_length</primary>
|
|
</indexterm>
|
|
<function>jsonb_array_length</function> ( <type>jsonb</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of elements in the top-level JSON array.
|
|
</para>
|
|
<para>
|
|
<literal>json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]')</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_array_length('[]')</literal>
|
|
<returnvalue>0</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_each</primary>
|
|
</indexterm>
|
|
<function>json_each</function> ( <type>json</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>key</parameter> <type>text</type>,
|
|
<parameter>value</parameter> <type>json</type> )
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_each</primary>
|
|
</indexterm>
|
|
<function>jsonb_each</function> ( <type>jsonb</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>key</parameter> <type>text</type>,
|
|
<parameter>value</parameter> <type>jsonb</type> )
|
|
</para>
|
|
<para>
|
|
Expands the top-level JSON object into a set of key/value pairs.
|
|
</para>
|
|
<para>
|
|
<literal>select * from json_each('{"a":"foo", "b":"bar"}')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
key | value
|
|
-----+-------
|
|
a | "foo"
|
|
b | "bar"
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_each_text</primary>
|
|
</indexterm>
|
|
<function>json_each_text</function> ( <type>json</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>key</parameter> <type>text</type>,
|
|
<parameter>value</parameter> <type>text</type> )
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_each_text</primary>
|
|
</indexterm>
|
|
<function>jsonb_each_text</function> ( <type>jsonb</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>key</parameter> <type>text</type>,
|
|
<parameter>value</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Expands the top-level JSON object into a set of key/value pairs.
|
|
The returned <parameter>value</parameter>s will be of
|
|
type <type>text</type>.
|
|
</para>
|
|
<para>
|
|
<literal>select * from json_each_text('{"a":"foo", "b":"bar"}')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
key | value
|
|
-----+-------
|
|
a | foo
|
|
b | bar
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_extract_path</primary>
|
|
</indexterm>
|
|
<function>json_extract_path</function> ( <parameter>from_json</parameter> <type>json</type>, <literal>VARIADIC</literal> <parameter>path_elems</parameter> <type>text[]</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_extract_path</primary>
|
|
</indexterm>
|
|
<function>jsonb_extract_path</function> ( <parameter>from_json</parameter> <type>jsonb</type>, <literal>VARIADIC</literal> <parameter>path_elems</parameter> <type>text[]</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts JSON sub-object at the specified path.
|
|
(This is functionally equivalent to the <literal>#></literal>
|
|
operator, but writing the path out as a variadic list can be more
|
|
convenient in some cases.)
|
|
</para>
|
|
<para>
|
|
<literal>json_extract_path('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6')</literal>
|
|
<returnvalue>"foo"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_extract_path_text</primary>
|
|
</indexterm>
|
|
<function>json_extract_path_text</function> ( <parameter>from_json</parameter> <type>json</type>, <literal>VARIADIC</literal> <parameter>path_elems</parameter> <type>text[]</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_extract_path_text</primary>
|
|
</indexterm>
|
|
<function>jsonb_extract_path_text</function> ( <parameter>from_json</parameter> <type>jsonb</type>, <literal>VARIADIC</literal> <parameter>path_elems</parameter> <type>text[]</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts JSON sub-object at the specified path as <type>text</type>.
|
|
(This is functionally equivalent to the <literal>#>></literal>
|
|
operator.)
|
|
</para>
|
|
<para>
|
|
<literal>json_extract_path_text('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6')</literal>
|
|
<returnvalue>foo</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_object_keys</primary>
|
|
</indexterm>
|
|
<function>json_object_keys</function> ( <type>json</type> )
|
|
<returnvalue>setof text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_object_keys</primary>
|
|
</indexterm>
|
|
<function>jsonb_object_keys</function> ( <type>jsonb</type> )
|
|
<returnvalue>setof text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the set of keys in the top-level JSON object.
|
|
</para>
|
|
<para>
|
|
<literal>select * from json_object_keys('{"f1":"abc","f2":{"f3":"a", "f4":"b"}}')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
json_object_keys
|
|
------------------
|
|
f1
|
|
f2
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_populate_record</primary>
|
|
</indexterm>
|
|
<function>json_populate_record</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>json</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_populate_record</primary>
|
|
</indexterm>
|
|
<function>jsonb_populate_record</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>jsonb</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Expands the top-level JSON object to a row having the composite type
|
|
of the <parameter>base</parameter> argument. The JSON object
|
|
is scanned for fields whose names match column names of the output row
|
|
type, and their values are inserted into those columns of the output.
|
|
(Fields that do not correspond to any output column name are ignored.)
|
|
In typical use, the value of <parameter>base</parameter> is just
|
|
<literal>NULL</literal>, which means that any output columns that do
|
|
not match any object field will be filled with nulls. However,
|
|
if <parameter>base</parameter> isn't <literal>NULL</literal> then
|
|
the values it contains will be used for unmatched columns.
|
|
</para>
|
|
<para>
|
|
To convert a JSON value to the SQL type of an output column, the
|
|
following rules are applied in sequence:
|
|
<itemizedlist spacing="compact">
|
|
<listitem>
|
|
<para>
|
|
A JSON null value is converted to an SQL null in all cases.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
If the output column is of type <type>json</type>
|
|
or <type>jsonb</type>, the JSON value is just reproduced exactly.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
If the output column is a composite (row) type, and the JSON value
|
|
is a JSON object, the fields of the object are converted to columns
|
|
of the output row type by recursive application of these rules.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Likewise, if the output column is an array type and the JSON value
|
|
is a JSON array, the elements of the JSON array are converted to
|
|
elements of the output array by recursive application of these
|
|
rules.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Otherwise, if the JSON value is a string, the contents of the
|
|
string are fed to the input conversion function for the column's
|
|
data type.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Otherwise, the ordinary text representation of the JSON value is
|
|
fed to the input conversion function for the column's data type.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
<para>
|
|
While the example below uses a constant JSON value, typical use would
|
|
be to reference a <type>json</type> or <type>jsonb</type> column
|
|
laterally from another table in the query's <literal>FROM</literal>
|
|
clause. Writing <function>json_populate_record</function> in
|
|
the <literal>FROM</literal> clause is good practice, since all of the
|
|
extracted columns are available for use without duplicate function
|
|
calls.
|
|
</para>
|
|
<para>
|
|
<literal>create type subrowtype as (d int, e text);</literal>
|
|
<literal>create type myrowtype as (a int, b text[], c subrowtype);</literal>
|
|
</para>
|
|
<para>
|
|
<literal>select * from json_populate_record(null::myrowtype,
|
|
'{"a": 1, "b": ["2", "a b"], "c": {"d": 4, "e": "a b c"}, "x": "foo"}')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
a | b | c
|
|
---+-----------+-------------
|
|
1 | {2,"a b"} | (4,"a b c")
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_populate_record_valid</primary>
|
|
</indexterm>
|
|
<function>jsonb_populate_record_valid</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>json</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Function for testing <function>jsonb_populate_record</function>. Returns
|
|
<literal>true</literal> if the input <function>jsonb_populate_record</function>
|
|
would finish without an error for the given input JSON object; that is, it's
|
|
valid input, <literal>false</literal> otherwise.
|
|
</para>
|
|
<para>
|
|
<literal>create type jsb_char2 as (a char(2));</literal>
|
|
</para>
|
|
<para>
|
|
<literal>select jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aaa"}');</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
jsonb_populate_record_valid
|
|
-----------------------------
|
|
f
|
|
(1 row)
|
|
</programlisting>
|
|
|
|
<literal>select * from jsonb_populate_record(NULL::jsb_char2, '{"a": "aaa"}') q;</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
ERROR: value too long for type character(2)
|
|
</programlisting>
|
|
<literal>select jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aa"}');</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
jsonb_populate_record_valid
|
|
-----------------------------
|
|
t
|
|
(1 row)
|
|
</programlisting>
|
|
|
|
<literal>select * from jsonb_populate_record(NULL::jsb_char2, '{"a": "aa"}') q;</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
a
|
|
----
|
|
aa
|
|
(1 row)
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_populate_recordset</primary>
|
|
</indexterm>
|
|
<function>json_populate_recordset</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>json</type> )
|
|
<returnvalue>setof anyelement</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_populate_recordset</primary>
|
|
</indexterm>
|
|
<function>jsonb_populate_recordset</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>jsonb</type> )
|
|
<returnvalue>setof anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Expands the top-level JSON array of objects to a set of rows having
|
|
the composite type of the <parameter>base</parameter> argument.
|
|
Each element of the JSON array is processed as described above
|
|
for <function>json[b]_populate_record</function>.
|
|
</para>
|
|
<para>
|
|
<literal>create type twoints as (a int, b int);</literal>
|
|
</para>
|
|
<para>
|
|
<literal>select * from json_populate_recordset(null::twoints, '[{"a":1,"b":2}, {"a":3,"b":4}]')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
a | b
|
|
---+---
|
|
1 | 2
|
|
3 | 4
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_to_record</primary>
|
|
</indexterm>
|
|
<function>json_to_record</function> ( <type>json</type> )
|
|
<returnvalue>record</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_to_record</primary>
|
|
</indexterm>
|
|
<function>jsonb_to_record</function> ( <type>jsonb</type> )
|
|
<returnvalue>record</returnvalue>
|
|
</para>
|
|
<para>
|
|
Expands the top-level JSON object to a row having the composite type
|
|
defined by an <literal>AS</literal> clause. (As with all functions
|
|
returning <type>record</type>, the calling query must explicitly
|
|
define the structure of the record with an <literal>AS</literal>
|
|
clause.) The output record is filled from fields of the JSON object,
|
|
in the same way as described above
|
|
for <function>json[b]_populate_record</function>. Since there is no
|
|
input record value, unmatched columns are always filled with nulls.
|
|
</para>
|
|
<para>
|
|
<literal>create type myrowtype as (a int, b text);</literal>
|
|
</para>
|
|
<para>
|
|
<literal>select * from json_to_record('{"a":1,"b":[1,2,3],"c":[1,2,3],"e":"bar","r": {"a": 123, "b": "a b c"}}') as x(a int, b text, c int[], d text, r myrowtype)</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
a | b | c | d | r
|
|
---+---------+---------+---+---------------
|
|
1 | [1,2,3] | {1,2,3} | | (123,"a b c")
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_to_recordset</primary>
|
|
</indexterm>
|
|
<function>json_to_recordset</function> ( <type>json</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_to_recordset</primary>
|
|
</indexterm>
|
|
<function>jsonb_to_recordset</function> ( <type>jsonb</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
</para>
|
|
<para>
|
|
Expands the top-level JSON array of objects to a set of rows having
|
|
the composite type defined by an <literal>AS</literal> clause. (As
|
|
with all functions returning <type>record</type>, the calling query
|
|
must explicitly define the structure of the record with
|
|
an <literal>AS</literal> clause.) Each element of the JSON array is
|
|
processed as described above
|
|
for <function>json[b]_populate_record</function>.
|
|
</para>
|
|
<para>
|
|
<literal>select * from json_to_recordset('[{"a":1,"b":"foo"}, {"a":"2","c":"bar"}]') as x(a int, b text)</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
a | b
|
|
---+-----
|
|
1 | foo
|
|
2 |
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_set</primary>
|
|
</indexterm>
|
|
<function>jsonb_set</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>text[]</type>, <parameter>new_value</parameter> <type>jsonb</type> <optional>, <parameter>create_if_missing</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns <parameter>target</parameter>
|
|
with the item designated by <parameter>path</parameter>
|
|
replaced by <parameter>new_value</parameter>, or with
|
|
<parameter>new_value</parameter> added if
|
|
<parameter>create_if_missing</parameter> is true (which is the
|
|
default) and the item designated by <parameter>path</parameter>
|
|
does not exist.
|
|
All earlier steps in the path must exist, or
|
|
the <parameter>target</parameter> is returned unchanged.
|
|
As with the path oriented operators, negative integers that
|
|
appear in the <parameter>path</parameter> count from the end
|
|
of JSON arrays.
|
|
If the last path step is an array index that is out of range,
|
|
and <parameter>create_if_missing</parameter> is true, the new
|
|
value is added at the beginning of the array if the index is negative,
|
|
or at the end of the array if it is positive.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_set('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', '[2,3,4]', false)</literal>
|
|
<returnvalue>[{"f1": [2, 3, 4], "f2": null}, 2, null, 3]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_set('[{"f1":1,"f2":null},2]', '{0,f3}', '[2,3,4]')</literal>
|
|
<returnvalue>[{"f1": 1, "f2": null, "f3": [2, 3, 4]}, 2]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_set_lax</primary>
|
|
</indexterm>
|
|
<function>jsonb_set_lax</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>text[]</type>, <parameter>new_value</parameter> <type>jsonb</type> <optional>, <parameter>create_if_missing</parameter> <type>boolean</type> <optional>, <parameter>null_value_treatment</parameter> <type>text</type> </optional></optional> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
If <parameter>new_value</parameter> is not <literal>NULL</literal>,
|
|
behaves identically to <literal>jsonb_set</literal>. Otherwise behaves
|
|
according to the value
|
|
of <parameter>null_value_treatment</parameter> which must be one
|
|
of <literal>'raise_exception'</literal>,
|
|
<literal>'use_json_null'</literal>, <literal>'delete_key'</literal>, or
|
|
<literal>'return_target'</literal>. The default is
|
|
<literal>'use_json_null'</literal>.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_set_lax('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', null)</literal>
|
|
<returnvalue>[{"f1": null, "f2": null}, 2, null, 3]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_set_lax('[{"f1":99,"f2":null},2]', '{0,f3}', null, true, 'return_target')</literal>
|
|
<returnvalue>[{"f1": 99, "f2": null}, 2]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_insert</primary>
|
|
</indexterm>
|
|
<function>jsonb_insert</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>text[]</type>, <parameter>new_value</parameter> <type>jsonb</type> <optional>, <parameter>insert_after</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns <parameter>target</parameter>
|
|
with <parameter>new_value</parameter> inserted. If the item
|
|
designated by the <parameter>path</parameter> is an array
|
|
element, <parameter>new_value</parameter> will be inserted before
|
|
that item if <parameter>insert_after</parameter> is false (which
|
|
is the default), or after it
|
|
if <parameter>insert_after</parameter> is true. If the item
|
|
designated by the <parameter>path</parameter> is an object
|
|
field, <parameter>new_value</parameter> will be inserted only if
|
|
the object does not already contain that key.
|
|
All earlier steps in the path must exist, or
|
|
the <parameter>target</parameter> is returned unchanged.
|
|
As with the path oriented operators, negative integers that
|
|
appear in the <parameter>path</parameter> count from the end
|
|
of JSON arrays.
|
|
If the last path step is an array index that is out of range, the new
|
|
value is added at the beginning of the array if the index is negative,
|
|
or at the end of the array if it is positive.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"')</literal>
|
|
<returnvalue>{"a": [0, "new_value", 1, 2]}</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"', true)</literal>
|
|
<returnvalue>{"a": [0, 1, "new_value", 2]}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_strip_nulls</primary>
|
|
</indexterm>
|
|
<function>json_strip_nulls</function> ( <type>json</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_strip_nulls</primary>
|
|
</indexterm>
|
|
<function>jsonb_strip_nulls</function> ( <type>jsonb</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Deletes all object fields that have null values from the given JSON
|
|
value, recursively. Null values that are not object fields are
|
|
untouched.
|
|
</para>
|
|
<para>
|
|
<literal>json_strip_nulls('[{"f1":1, "f2":null}, 2, null, 3]')</literal>
|
|
<returnvalue>[{"f1":1},2,null,3]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_exists</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_exists</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Checks whether the JSON path returns any item for the specified JSON
|
|
value.
|
|
(This is useful only with SQL-standard JSON path expressions, not
|
|
<link linkend="functions-sqljson-check-expressions">predicate check
|
|
expressions</link>, since those always return a value.)
|
|
If the <parameter>vars</parameter> argument is specified, it must
|
|
be a JSON object, and its fields provide named values to be
|
|
substituted into the <type>jsonpath</type> expression.
|
|
If the <parameter>silent</parameter> argument is specified and
|
|
is <literal>true</literal>, the function suppresses the same errors
|
|
as the <literal>@?</literal> and <literal>@@</literal> operators do.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_exists('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_match</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_match</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the result of a JSON path predicate check for the specified
|
|
JSON value.
|
|
(This is useful only
|
|
with <link linkend="functions-sqljson-check-expressions">predicate
|
|
check expressions</link>, not SQL-standard JSON path expressions,
|
|
since it will either fail or return <literal>NULL</literal> if the
|
|
path result is not a single boolean value.)
|
|
The optional <parameter>vars</parameter>
|
|
and <parameter>silent</parameter> arguments act the same as
|
|
for <function>jsonb_path_exists</function>.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_match('{"a":[1,2,3,4,5]}', 'exists($.a[*] ? (@ >= $min && @ <= $max))', '{"min":2, "max":4}')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_query</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_query</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>setof jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns all JSON items returned by the JSON path for the specified
|
|
JSON value.
|
|
For SQL-standard JSON path expressions it returns the JSON
|
|
values selected from <parameter>target</parameter>.
|
|
For <link linkend="functions-sqljson-check-expressions">predicate
|
|
check expressions</link> it returns the result of the predicate
|
|
check: <literal>true</literal>, <literal>false</literal>,
|
|
or <literal>null</literal>.
|
|
The optional <parameter>vars</parameter>
|
|
and <parameter>silent</parameter> arguments act the same as
|
|
for <function>jsonb_path_exists</function>.
|
|
</para>
|
|
<para>
|
|
<literal>select * from jsonb_path_query('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
jsonb_path_query
|
|
------------------
|
|
2
|
|
3
|
|
4
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_query_array</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_query_array</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns all JSON items returned by the JSON path for the specified
|
|
JSON value, as a JSON array.
|
|
The parameters are the same as
|
|
for <function>jsonb_path_query</function>.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}')</literal>
|
|
<returnvalue>[2, 3, 4]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_query_first</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_query_first</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the first JSON item returned by the JSON path for the
|
|
specified JSON value, or <literal>NULL</literal> if there are no
|
|
results.
|
|
The parameters are the same as
|
|
for <function>jsonb_path_query</function>.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_first('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}')</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_exists_tz</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_exists_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_match_tz</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_match_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_query_tz</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_query_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>setof jsonb</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_query_array_tz</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_query_array_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_path_query_first_tz</primary>
|
|
</indexterm>
|
|
<function>jsonb_path_query_first_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
These functions act like their counterparts described above without
|
|
the <literal>_tz</literal> suffix, except that these functions support
|
|
comparisons of date/time values that require timezone-aware
|
|
conversions. The example below requires interpretation of the
|
|
date-only value <literal>2015-08-02</literal> as a timestamp with time
|
|
zone, so the result depends on the current
|
|
<xref linkend="guc-timezone"/> setting. Due to this dependency, these
|
|
functions are marked as stable, which means these functions cannot be
|
|
used in indexes. Their counterparts are immutable, and so can be used
|
|
in indexes; but they will throw errors if asked to make such
|
|
comparisons.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_exists_tz('["2015-08-01 12:00:00-05"]', '$[*] ? (@.datetime() < "2015-08-02".datetime())')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_pretty</primary>
|
|
</indexterm>
|
|
<function>jsonb_pretty</function> ( <type>jsonb</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the given JSON value to pretty-printed, indented text.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_pretty('[{"f1":1,"f2":null}, 2]')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
[
|
|
{
|
|
"f1": 1,
|
|
"f2": null
|
|
},
|
|
2
|
|
]
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_typeof</primary>
|
|
</indexterm>
|
|
<function>json_typeof</function> ( <type>json</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_typeof</primary>
|
|
</indexterm>
|
|
<function>jsonb_typeof</function> ( <type>jsonb</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the type of the top-level JSON value as a text string.
|
|
Possible types are
|
|
<literal>object</literal>, <literal>array</literal>,
|
|
<literal>string</literal>, <literal>number</literal>,
|
|
<literal>boolean</literal>, and <literal>null</literal>.
|
|
(The <literal>null</literal> result should not be confused
|
|
with an SQL NULL; see the examples.)
|
|
</para>
|
|
<para>
|
|
<literal>json_typeof('-123.4')</literal>
|
|
<returnvalue>number</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>json_typeof('null'::json)</literal>
|
|
<returnvalue>null</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>json_typeof(NULL::json) IS NULL</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-sqljson-path">
|
|
<title>The SQL/JSON Path Language</title>
|
|
|
|
<indexterm zone="functions-sqljson-path">
|
|
<primary>SQL/JSON path language</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
SQL/JSON path expressions specify item(s) to be retrieved
|
|
from a JSON value, similarly to XPath expressions used
|
|
for access to XML content. In <productname>PostgreSQL</productname>,
|
|
path expressions are implemented as the <type>jsonpath</type>
|
|
data type and can use any elements described in
|
|
<xref linkend="datatype-jsonpath"/>.
|
|
</para>
|
|
|
|
<para>
|
|
JSON query functions and operators
|
|
pass the provided path expression to the <firstterm>path engine</firstterm>
|
|
for evaluation. If the expression matches the queried JSON data,
|
|
the corresponding JSON item, or set of items, is returned.
|
|
If there is no match, the result will be <literal>NULL</literal>,
|
|
<literal>false</literal>, or an error, depending on the function.
|
|
Path expressions are written in the SQL/JSON path language
|
|
and can include arithmetic expressions and functions.
|
|
</para>
|
|
|
|
<para>
|
|
A path expression consists of a sequence of elements allowed
|
|
by the <type>jsonpath</type> data type.
|
|
The path expression is normally evaluated from left to right, but
|
|
you can use parentheses to change the order of operations.
|
|
If the evaluation is successful, a sequence of JSON items is produced,
|
|
and the evaluation result is returned to the JSON query function
|
|
that completes the specified computation.
|
|
</para>
|
|
|
|
<para>
|
|
To refer to the JSON value being queried (the
|
|
<firstterm>context item</firstterm>), use the <literal>$</literal> variable
|
|
in the path expression. The first element of a path must always
|
|
be <literal>$</literal>. It can be followed by one or more
|
|
<link linkend="type-jsonpath-accessors">accessor operators</link>,
|
|
which go down the JSON structure level by level to retrieve sub-items
|
|
of the context item. Each accessor operator acts on the
|
|
result(s) of the previous evaluation step, producing zero, one, or more
|
|
output items from each input item.
|
|
</para>
|
|
|
|
<para>
|
|
For example, suppose you have some JSON data from a GPS tracker that you
|
|
would like to parse, such as:
|
|
<programlisting>
|
|
SELECT '{
|
|
"track": {
|
|
"segments": [
|
|
{
|
|
"location": [ 47.763, 13.4034 ],
|
|
"start time": "2018-10-14 10:05:14",
|
|
"HR": 73
|
|
},
|
|
{
|
|
"location": [ 47.706, 13.2635 ],
|
|
"start time": "2018-10-14 10:39:21",
|
|
"HR": 135
|
|
}
|
|
]
|
|
}
|
|
}' AS json \gset
|
|
</programlisting>
|
|
(The above example can be copied-and-pasted
|
|
into <application>psql</application> to set things up for the following
|
|
examples. Then <application>psql</application> will
|
|
expand <literal>:'json'</literal> into a suitably-quoted string
|
|
constant containing the JSON value.)
|
|
</para>
|
|
|
|
<para>
|
|
To retrieve the available track segments, you need to use the
|
|
<literal>.<replaceable>key</replaceable></literal> accessor
|
|
operator to descend through surrounding JSON objects, for example:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments');</userinput>
|
|
jsonb_path_query
|
|
-----------------------------------------------------------&zwsp;-----------------------------------------------------------&zwsp;---------------------------------------------
|
|
[{"HR": 73, "location": [47.763, 13.4034], "start time": "2018-10-14 10:05:14"}, {"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"}]
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
To retrieve the contents of an array, you typically use the
|
|
<literal>[*]</literal> operator.
|
|
The following example will return the location coordinates for all
|
|
the available track segments:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments[*].location');</userinput>
|
|
jsonb_path_query
|
|
-------------------
|
|
[47.763, 13.4034]
|
|
[47.706, 13.2635]
|
|
</screen>
|
|
Here we started with the whole JSON input value (<literal>$</literal>),
|
|
then the <literal>.track</literal> accessor selected the JSON object
|
|
associated with the <literal>"track"</literal> object key, then
|
|
the <literal>.segments</literal> accessor selected the JSON array
|
|
associated with the <literal>"segments"</literal> key within that
|
|
object, then the <literal>[*]</literal> accessor selected each element
|
|
of that array (producing a series of items), then
|
|
the <literal>.location</literal> accessor selected the JSON array
|
|
associated with the <literal>"location"</literal> key within each of
|
|
those objects. In this example, each of those objects had
|
|
a <literal>"location"</literal> key; but if any of them did not,
|
|
the <literal>.location</literal> accessor would have simply produced no
|
|
output for that input item.
|
|
</para>
|
|
|
|
<para>
|
|
To return the coordinates of the first segment only, you can
|
|
specify the corresponding subscript in the <literal>[]</literal>
|
|
accessor operator. Recall that JSON array indexes are 0-relative:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments[0].location');</userinput>
|
|
jsonb_path_query
|
|
-------------------
|
|
[47.763, 13.4034]
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
The result of each path evaluation step can be processed
|
|
by one or more of the <type>jsonpath</type> operators and methods
|
|
listed in <xref linkend="functions-sqljson-path-operators"/>.
|
|
Each method name must be preceded by a dot. For example,
|
|
you can get the size of an array:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments.size()');</userinput>
|
|
jsonb_path_query
|
|
------------------
|
|
2
|
|
</screen>
|
|
More examples of using <type>jsonpath</type> operators
|
|
and methods within path expressions appear below in
|
|
<xref linkend="functions-sqljson-path-operators"/>.
|
|
</para>
|
|
|
|
<para>
|
|
A path can also contain
|
|
<firstterm>filter expressions</firstterm> that work similarly to the
|
|
<literal>WHERE</literal> clause in SQL. A filter expression begins with
|
|
a question mark and provides a condition in parentheses:
|
|
|
|
<synopsis>
|
|
? (<replaceable>condition</replaceable>)
|
|
</synopsis>
|
|
</para>
|
|
|
|
<para>
|
|
Filter expressions must be written just after the path evaluation step
|
|
to which they should apply. The result of that step is filtered to include
|
|
only those items that satisfy the provided condition. SQL/JSON defines
|
|
three-valued logic, so the condition can
|
|
produce <literal>true</literal>, <literal>false</literal>,
|
|
or <literal>unknown</literal>. The <literal>unknown</literal> value
|
|
plays the same role as SQL <literal>NULL</literal> and can be tested
|
|
for with the <literal>is unknown</literal> predicate. Further path
|
|
evaluation steps use only those items for which the filter expression
|
|
returned <literal>true</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
The functions and operators that can be used in filter expressions are
|
|
listed in <xref linkend="functions-sqljson-filter-ex-table"/>. Within a
|
|
filter expression, the <literal>@</literal> variable denotes the value
|
|
being considered (i.e., one result of the preceding path step). You can
|
|
write accessor operators after <literal>@</literal> to retrieve component
|
|
items.
|
|
</para>
|
|
|
|
<para>
|
|
For example, suppose you would like to retrieve all heart rate values higher
|
|
than 130. You can achieve this as follows:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments[*].HR ? (@ > 130)');</userinput>
|
|
jsonb_path_query
|
|
------------------
|
|
135
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
To get the start times of segments with such values, you have to
|
|
filter out irrelevant segments before selecting the start times, so the
|
|
filter expression is applied to the previous step, and the path used
|
|
in the condition is different:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments[*] ? (@.HR > 130)."start time"');</userinput>
|
|
jsonb_path_query
|
|
-----------------------
|
|
"2018-10-14 10:39:21"
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
You can use several filter expressions in sequence, if required.
|
|
The following example selects start times of all segments that
|
|
contain locations with relevant coordinates and high heart rate values:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] < 13.4) ? (@.HR > 130)."start time"');</userinput>
|
|
jsonb_path_query
|
|
-----------------------
|
|
"2018-10-14 10:39:21"
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
Using filter expressions at different nesting levels is also allowed.
|
|
The following example first filters all segments by location, and then
|
|
returns high heart rate values for these segments, if available:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] < 13.4).HR ? (@ > 130)');</userinput>
|
|
jsonb_path_query
|
|
------------------
|
|
135
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
You can also nest filter expressions within each other.
|
|
This example returns the size of the track if it contains any
|
|
segments with high heart rate values, or an empty sequence otherwise:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track ? (exists(@.segments[*] ? (@.HR > 130))).segments.size()');</userinput>
|
|
jsonb_path_query
|
|
------------------
|
|
2
|
|
</screen>
|
|
</para>
|
|
|
|
<sect3 id="functions-sqljson-deviations">
|
|
<title>Deviations from the SQL Standard</title>
|
|
<para>
|
|
<productname>PostgreSQL</productname>'s implementation of the SQL/JSON path
|
|
language has the following deviations from the SQL/JSON standard.
|
|
</para>
|
|
|
|
<sect4 id="functions-sqljson-check-expressions">
|
|
<title>Boolean Predicate Check Expressions</title>
|
|
<para>
|
|
As an extension to the SQL standard,
|
|
a <productname>PostgreSQL</productname> path expression can be a
|
|
Boolean predicate, whereas the SQL standard allows predicates only within
|
|
filters. While SQL-standard path expressions return the relevant
|
|
element(s) of the queried JSON value, predicate check expressions
|
|
return the single three-valued result of the
|
|
predicate: <literal>true</literal>,
|
|
<literal>false</literal>, or <literal>unknown</literal>.
|
|
For example, we could write this SQL-standard filter expression:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments ?(@[*].HR > 130)');</userinput>
|
|
jsonb_path_query
|
|
-----------------------------------------------------------&zwsp;----------------------
|
|
{"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"}
|
|
</screen>
|
|
The similar predicate check expression simply
|
|
returns <literal>true</literal>, indicating that a match exists:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', '$.track.segments[*].HR > 130');</userinput>
|
|
jsonb_path_query
|
|
------------------
|
|
true
|
|
</screen>
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
Predicate check expressions are required in the
|
|
<literal>@@</literal> operator (and the
|
|
<function>jsonb_path_match</function> function), and should not be used
|
|
with the <literal>@?</literal> operator (or the
|
|
<function>jsonb_path_exists</function> function).
|
|
</para>
|
|
</note>
|
|
</sect4>
|
|
|
|
<sect4 id="functions-sqljson-regular-expression-deviation">
|
|
<title>Regular Expression Interpretation</title>
|
|
<para>
|
|
There are minor differences in the interpretation of regular
|
|
expression patterns used in <literal>like_regex</literal> filters, as
|
|
described in <xref linkend="jsonpath-regular-expressions"/>.
|
|
</para>
|
|
</sect4>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-sqljson-strict-and-lax-modes">
|
|
<title>Strict and Lax Modes</title>
|
|
<para>
|
|
When you query JSON data, the path expression may not match the
|
|
actual JSON data structure. An attempt to access a non-existent
|
|
member of an object or element of an array is defined as a
|
|
structural error. SQL/JSON path expressions have two modes
|
|
of handling structural errors:
|
|
</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
lax (default) — the path engine implicitly adapts
|
|
the queried data to the specified path.
|
|
Any structural errors that cannot be fixed as described below
|
|
are suppressed, producing no match.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
strict — if a structural error occurs, an error is raised.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>
|
|
Lax mode facilitates matching of a JSON document and path
|
|
expression when the JSON data does not conform to the expected schema.
|
|
If an operand does not match the requirements of a particular operation,
|
|
it can be automatically wrapped as an SQL/JSON array, or unwrapped by
|
|
converting its elements into an SQL/JSON sequence before performing
|
|
the operation. Also, comparison operators automatically unwrap their
|
|
operands in lax mode, so you can compare SQL/JSON arrays
|
|
out-of-the-box. An array of size 1 is considered equal to its sole element.
|
|
Automatic unwrapping is not performed when:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
The path expression contains <literal>type()</literal> or
|
|
<literal>size()</literal> methods that return the type
|
|
and the number of elements in the array, respectively.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
The queried JSON data contain nested arrays. In this case, only
|
|
the outermost array is unwrapped, while all the inner arrays
|
|
remain unchanged. Thus, implicit unwrapping can only go one
|
|
level down within each path evaluation step.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
For example, when querying the GPS data listed above, you can
|
|
abstract from the fact that it stores an array of segments
|
|
when using lax mode:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', 'lax $.track.segments.location');</userinput>
|
|
jsonb_path_query
|
|
-------------------
|
|
[47.763, 13.4034]
|
|
[47.706, 13.2635]
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
In strict mode, the specified path must exactly match the structure of
|
|
the queried JSON document, so using this path
|
|
expression will cause an error:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', 'strict $.track.segments.location');</userinput>
|
|
ERROR: jsonpath member accessor can only be applied to an object
|
|
</screen>
|
|
To get the same result as in lax mode, you have to explicitly unwrap the
|
|
<literal>segments</literal> array:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', 'strict $.track.segments[*].location');</userinput>
|
|
jsonb_path_query
|
|
-------------------
|
|
[47.763, 13.4034]
|
|
[47.706, 13.2635]
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
The unwrapping behavior of lax mode can lead to surprising results. For
|
|
instance, the following query using the <literal>.**</literal> accessor
|
|
selects every <literal>HR</literal> value twice:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', 'lax $.**.HR');</userinput>
|
|
jsonb_path_query
|
|
------------------
|
|
73
|
|
135
|
|
73
|
|
135
|
|
</screen>
|
|
This happens because the <literal>.**</literal> accessor selects both
|
|
the <literal>segments</literal> array and each of its elements, while
|
|
the <literal>.HR</literal> accessor automatically unwraps arrays when
|
|
using lax mode. To avoid surprising results, we recommend using
|
|
the <literal>.**</literal> accessor only in strict mode. The
|
|
following query selects each <literal>HR</literal> value just once:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', 'strict $.**.HR');</userinput>
|
|
jsonb_path_query
|
|
------------------
|
|
73
|
|
135
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
The unwrapping of arrays can also lead to unexpected results. Consider this
|
|
example, which selects all the <literal>location</literal> arrays:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', 'lax $.track.segments[*].location');</userinput>
|
|
jsonb_path_query
|
|
-------------------
|
|
[47.763, 13.4034]
|
|
[47.706, 13.2635]
|
|
(2 rows)
|
|
</screen>
|
|
As expected it returns the full arrays. But applying a filter expression
|
|
causes the arrays to be unwrapped to evaluate each item, returning only the
|
|
items that match the expression:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', 'lax $.track.segments[*].location ?(@[*] > 15)');</userinput>
|
|
jsonb_path_query
|
|
------------------
|
|
47.763
|
|
47.706
|
|
(2 rows)
|
|
</screen>
|
|
This despite the fact that the full arrays are selected by the path
|
|
expression. Use strict mode to restore selecting the arrays:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>select jsonb_path_query(:'json', 'strict $.track.segments[*].location ?(@[*] > 15)');</userinput>
|
|
jsonb_path_query
|
|
-------------------
|
|
[47.763, 13.4034]
|
|
[47.706, 13.2635]
|
|
(2 rows)
|
|
</screen>
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3 id="functions-sqljson-path-operators">
|
|
<title>SQL/JSON Path Operators and Methods</title>
|
|
|
|
<para>
|
|
<xref linkend="functions-sqljson-op-table"/> shows the operators and
|
|
methods available in <type>jsonpath</type>. Note that while the unary
|
|
operators and methods can be applied to multiple values resulting from a
|
|
preceding path step, the binary operators (addition etc.) can only be
|
|
applied to single values.
|
|
</para>
|
|
|
|
<table id="functions-sqljson-op-table">
|
|
<title><type>jsonpath</type> Operators and Methods</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator/Method
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>number</replaceable> <literal>+</literal> <replaceable>number</replaceable>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Addition
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[2]', '$[0] + 3')</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>+</literal> <replaceable>number</replaceable>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Unary plus (no operation); unlike addition, this can iterate over
|
|
multiple values
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('{"x": [2,3,4]}', '+ $.x')</literal>
|
|
<returnvalue>[2, 3, 4]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>number</replaceable> <literal>-</literal> <replaceable>number</replaceable>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Subtraction
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[2]', '7 - $[0]')</literal>
|
|
<returnvalue>5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>-</literal> <replaceable>number</replaceable>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Negation; unlike subtraction, this can iterate over
|
|
multiple values
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('{"x": [2,3,4]}', '- $.x')</literal>
|
|
<returnvalue>[-2, -3, -4]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>number</replaceable> <literal>*</literal> <replaceable>number</replaceable>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Multiplication
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[4]', '2 * $[0]')</literal>
|
|
<returnvalue>8</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>number</replaceable> <literal>/</literal> <replaceable>number</replaceable>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Division
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[8.5]', '$[0] / 2')</literal>
|
|
<returnvalue>4.2500000000000000</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>number</replaceable> <literal>%</literal> <replaceable>number</replaceable>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Modulo (remainder)
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[32]', '$[0] % 10')</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>.</literal> <literal>type()</literal>
|
|
<returnvalue><replaceable>string</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Type of the JSON item (see <function>json_typeof</function>)
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('[1, "2", {}]', '$[*].type()')</literal>
|
|
<returnvalue>["number", "string", "object"]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>.</literal> <literal>size()</literal>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Size of the JSON item (number of array elements, or 1 if not an
|
|
array)
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('{"m": [11, 15]}', '$.m.size()')</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>.</literal> <literal>boolean()</literal>
|
|
<returnvalue><replaceable>boolean</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Boolean value converted from a JSON boolean, number, or string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('[1, "yes", false]', '$[*].boolean()')</literal>
|
|
<returnvalue>[true, true, false]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>.</literal> <literal>string()</literal>
|
|
<returnvalue><replaceable>string</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
String value converted from a JSON boolean, number, string, or datetime
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('[1.23, "xyz", false]', '$[*].string()')</literal>
|
|
<returnvalue>["1.23", "xyz", "false"]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"2023-08-15"', '$.datetime().string()')</literal>
|
|
<returnvalue>"2023-08-15"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>.</literal> <literal>double()</literal>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Approximate floating-point number converted from a JSON number or
|
|
string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('{"len": "1.9"}', '$.len.double() * 2')</literal>
|
|
<returnvalue>3.8</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>number</replaceable> <literal>.</literal> <literal>ceiling()</literal>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Nearest integer greater than or equal to the given number
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('{"h": 1.3}', '$.h.ceiling()')</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>number</replaceable> <literal>.</literal> <literal>floor()</literal>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Nearest integer less than or equal to the given number
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('{"h": 1.7}', '$.h.floor()')</literal>
|
|
<returnvalue>1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>number</replaceable> <literal>.</literal> <literal>abs()</literal>
|
|
<returnvalue><replaceable>number</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Absolute value of the given number
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('{"z": -0.3}', '$.z.abs()')</literal>
|
|
<returnvalue>0.3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>.</literal> <literal>bigint()</literal>
|
|
<returnvalue><replaceable>bigint</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Big integer value converted from a JSON number or string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('{"len": "9876543219"}', '$.len.bigint()')</literal>
|
|
<returnvalue>9876543219</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>.</literal> <literal>decimal( [ <replaceable>precision</replaceable> [ , <replaceable>scale</replaceable> ] ] )</literal>
|
|
<returnvalue><replaceable>decimal</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Rounded decimal value converted from a JSON number or string. <literal>precision</literal> and <literal>scale</literal> must be integer values.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('1234.5678', '$.decimal(6, 2)')</literal>
|
|
<returnvalue>1234.57</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>.</literal> <literal>integer()</literal>
|
|
<returnvalue><replaceable>integer</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Integer value converted from a JSON number or string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('{"len": "12345"}', '$.len.integer()')</literal>
|
|
<returnvalue>12345</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>.</literal> <literal>number()</literal>
|
|
<returnvalue><replaceable>numeric</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Numeric value converted from a JSON number or string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('{"len": "123.45"}', '$.len.number()')</literal>
|
|
<returnvalue>123.45</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>datetime()</literal>
|
|
<returnvalue><replaceable>datetime_type</replaceable></returnvalue>
|
|
(see note)
|
|
</para>
|
|
<para>
|
|
Date/time value converted from a string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('["2015-8-1", "2015-08-12"]', '$[*] ? (@.datetime() < "2015-08-2".datetime())')</literal>
|
|
<returnvalue>"2015-8-1"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>datetime(<replaceable>template</replaceable>)</literal>
|
|
<returnvalue><replaceable>datetime_type</replaceable></returnvalue>
|
|
(see note)
|
|
</para>
|
|
<para>
|
|
Date/time value converted from a string using the
|
|
specified <function>to_timestamp</function> template
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('["12:30", "18:40"]', '$[*].datetime("HH24:MI")')</literal>
|
|
<returnvalue>["12:30:00", "18:40:00"]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>date()</literal>
|
|
<returnvalue><replaceable>date</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Date value converted from a string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"2023-08-15"', '$.date()')</literal>
|
|
<returnvalue>"2023-08-15"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>time()</literal>
|
|
<returnvalue><replaceable>time without time zone</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Time without time zone value converted from a string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"12:34:56"', '$.time()')</literal>
|
|
<returnvalue>"12:34:56"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>time(<replaceable>precision</replaceable>)</literal>
|
|
<returnvalue><replaceable>time without time zone</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Time without time zone value converted from a string, with fractional
|
|
seconds adjusted to the given precision.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"12:34:56.789"', '$.time(2)')</literal>
|
|
<returnvalue>"12:34:56.79"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>time_tz()</literal>
|
|
<returnvalue><replaceable>time with time zone</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Time with time zone value converted from a string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"12:34:56 +05:30"', '$.time_tz()')</literal>
|
|
<returnvalue>"12:34:56+05:30"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>time_tz(<replaceable>precision</replaceable>)</literal>
|
|
<returnvalue><replaceable>time with time zone</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Time with time zone value converted from a string, with fractional
|
|
seconds adjusted to the given precision.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"12:34:56.789 +05:30"', '$.time_tz(2)')</literal>
|
|
<returnvalue>"12:34:56.79+05:30"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>timestamp()</literal>
|
|
<returnvalue><replaceable>timestamp without time zone</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Timestamp without time zone value converted from a string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp()')</literal>
|
|
<returnvalue>"2023-08-15T12:34:56"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>timestamp(<replaceable>precision</replaceable>)</literal>
|
|
<returnvalue><replaceable>timestamp without time zone</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Timestamp without time zone value converted from a string, with
|
|
fractional seconds adjusted to the given precision.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"2023-08-15 12:34:56.789"', '$.timestamp(2)')</literal>
|
|
<returnvalue>"2023-08-15T12:34:56.79"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>timestamp_tz()</literal>
|
|
<returnvalue><replaceable>timestamp with time zone</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Timestamp with time zone value converted from a string
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"2023-08-15 12:34:56 +05:30"', '$.timestamp_tz()')</literal>
|
|
<returnvalue>"2023-08-15T12:34:56+05:30"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>.</literal> <literal>timestamp_tz(<replaceable>precision</replaceable>)</literal>
|
|
<returnvalue><replaceable>timestamp with time zone</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Timestamp with time zone value converted from a string, with fractional
|
|
seconds adjusted to the given precision.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('"2023-08-15 12:34:56.789 +05:30"', '$.timestamp_tz(2)')</literal>
|
|
<returnvalue>"2023-08-15T12:34:56.79+05:30"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>object</replaceable> <literal>.</literal> <literal>keyvalue()</literal>
|
|
<returnvalue><replaceable>array</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
The object's key-value pairs, represented as an array of objects
|
|
containing three fields: <literal>"key"</literal>,
|
|
<literal>"value"</literal>, and <literal>"id"</literal>;
|
|
<literal>"id"</literal> is a unique identifier of the object the
|
|
key-value pair belongs to
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('{"x": "20", "y": 32}', '$.keyvalue()')</literal>
|
|
<returnvalue>[{"id": 0, "key": "x", "value": "20"}, {"id": 0, "key": "y", "value": 32}]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>
|
|
The result type of the <literal>datetime()</literal> and
|
|
<literal>datetime(<replaceable>template</replaceable>)</literal>
|
|
methods can be <type>date</type>, <type>timetz</type>, <type>time</type>,
|
|
<type>timestamptz</type>, or <type>timestamp</type>.
|
|
Both methods determine their result type dynamically.
|
|
</para>
|
|
<para>
|
|
The <literal>datetime()</literal> method sequentially tries to
|
|
match its input string to the ISO formats
|
|
for <type>date</type>, <type>timetz</type>, <type>time</type>,
|
|
<type>timestamptz</type>, and <type>timestamp</type>. It stops on
|
|
the first matching format and emits the corresponding data type.
|
|
</para>
|
|
<para>
|
|
The <literal>datetime(<replaceable>template</replaceable>)</literal>
|
|
method determines the result type according to the fields used in the
|
|
provided template string.
|
|
</para>
|
|
<para>
|
|
The <literal>datetime()</literal> and
|
|
<literal>datetime(<replaceable>template</replaceable>)</literal> methods
|
|
use the same parsing rules as the <literal>to_timestamp</literal> SQL
|
|
function does (see <xref linkend="functions-formatting"/>), with three
|
|
exceptions. First, these methods don't allow unmatched template
|
|
patterns. Second, only the following separators are allowed in the
|
|
template string: minus sign, period, solidus (slash), comma, apostrophe,
|
|
semicolon, colon and space. Third, separators in the template string
|
|
must exactly match the input string.
|
|
</para>
|
|
<para>
|
|
If different date/time types need to be compared, an implicit cast is
|
|
applied. A <type>date</type> value can be cast to <type>timestamp</type>
|
|
or <type>timestamptz</type>, <type>timestamp</type> can be cast to
|
|
<type>timestamptz</type>, and <type>time</type> to <type>timetz</type>.
|
|
However, all but the first of these conversions depend on the current
|
|
<xref linkend="guc-timezone"/> setting, and thus can only be performed
|
|
within timezone-aware <type>jsonpath</type> functions. Similarly, other
|
|
date/time-related methods that convert strings to date/time types
|
|
also do this casting, which may involve the current
|
|
<xref linkend="guc-timezone"/> setting. Therefore, these conversions can
|
|
also only be performed within timezone-aware <type>jsonpath</type>
|
|
functions.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
<xref linkend="functions-sqljson-filter-ex-table"/> shows the available
|
|
filter expression elements.
|
|
</para>
|
|
|
|
<table id="functions-sqljson-filter-ex-table">
|
|
<title><type>jsonpath</type> Filter Expression Elements</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Predicate/Value
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>==</literal> <replaceable>value</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Equality comparison (this, and the other comparison operators, work on
|
|
all JSON scalar values)
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == 1)')</literal>
|
|
<returnvalue>[1, 1]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == "a")')</literal>
|
|
<returnvalue>["a"]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>!=</literal> <replaceable>value</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<replaceable>value</replaceable> <literal><></literal> <replaceable>value</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Non-equality comparison
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('[1, 2, 1, 3]', '$[*] ? (@ != 1)')</literal>
|
|
<returnvalue>[2, 3]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ <> "b")')</literal>
|
|
<returnvalue>["a", "c"]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal><</literal> <replaceable>value</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Less-than comparison
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ < 2)')</literal>
|
|
<returnvalue>[1]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal><=</literal> <replaceable>value</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Less-than-or-equal-to comparison
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ <= "b")')</literal>
|
|
<returnvalue>["a", "b"]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>></literal> <replaceable>value</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Greater-than comparison
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ > 2)')</literal>
|
|
<returnvalue>[3]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>value</replaceable> <literal>>=</literal> <replaceable>value</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Greater-than-or-equal-to comparison
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ >= 2)')</literal>
|
|
<returnvalue>[2, 3]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>true</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
JSON constant <literal>true</literal>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == true)')</literal>
|
|
<returnvalue>{"name": "Chris", "parent": true}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>false</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
JSON constant <literal>false</literal>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == false)')</literal>
|
|
<returnvalue>{"name": "John", "parent": false}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>null</literal>
|
|
<returnvalue><replaceable>value</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
JSON constant <literal>null</literal> (note that, unlike in SQL,
|
|
comparison to <literal>null</literal> works normally)
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[{"name": "Mary", "job": null}, {"name": "Michael", "job": "driver"}]', '$[*] ? (@.job == null) .name')</literal>
|
|
<returnvalue>"Mary"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>boolean</replaceable> <literal>&&</literal> <replaceable>boolean</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Boolean AND
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[1, 3, 7]', '$[*] ? (@ > 1 && @ < 5)')</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>boolean</replaceable> <literal>||</literal> <replaceable>boolean</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Boolean OR
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[1, 3, 7]', '$[*] ? (@ < 1 || @ > 5)')</literal>
|
|
<returnvalue>7</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>!</literal> <replaceable>boolean</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Boolean NOT
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[1, 3, 7]', '$[*] ? (!(@ < 5))')</literal>
|
|
<returnvalue>7</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>boolean</replaceable> <literal>is unknown</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tests whether a Boolean condition is <literal>unknown</literal>.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('[-1, 2, 7, "foo"]', '$[*] ? ((@ > 0) is unknown)')</literal>
|
|
<returnvalue>"foo"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>like_regex</literal> <replaceable>string</replaceable> <optional> <literal>flag</literal> <replaceable>string</replaceable> </optional>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tests whether the first operand matches the regular expression
|
|
given by the second operand, optionally with modifications
|
|
described by a string of <literal>flag</literal> characters (see
|
|
<xref linkend="jsonpath-regular-expressions"/>).
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c")')</literal>
|
|
<returnvalue>["abc", "abdacb"]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c" flag "i")')</literal>
|
|
<returnvalue>["abc", "aBdC", "abdacb"]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<replaceable>string</replaceable> <literal>starts with</literal> <replaceable>string</replaceable>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tests whether the second operand is an initial substring of the first
|
|
operand.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('["John Smith", "Mary Stone", "Bob Johnson"]', '$[*] ? (@ starts with "John")')</literal>
|
|
<returnvalue>"John Smith"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<literal>exists</literal> <literal>(</literal> <replaceable>path_expression</replaceable> <literal>)</literal>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tests whether a path expression matches at least one SQL/JSON item.
|
|
Returns <literal>unknown</literal> if the path expression would result
|
|
in an error; the second example uses this to avoid a no-such-key error
|
|
in strict mode.
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query('{"x": [1, 2], "y": [2, 4]}', 'strict $.* ? (exists (@ ? (@[*] > 2)))')</literal>
|
|
<returnvalue>[2, 4]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>jsonb_path_query_array('{"value": 41}', 'strict $ ? (exists (@.name)) .name')</literal>
|
|
<returnvalue>[]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect3>
|
|
|
|
<sect3 id="jsonpath-regular-expressions">
|
|
<title>SQL/JSON Regular Expressions</title>
|
|
|
|
<indexterm zone="jsonpath-regular-expressions">
|
|
<primary><literal>LIKE_REGEX</literal></primary>
|
|
<secondary>in SQL/JSON</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
SQL/JSON path expressions allow matching text to a regular expression
|
|
with the <literal>like_regex</literal> filter. For example, the
|
|
following SQL/JSON path query would case-insensitively match all
|
|
strings in an array that start with an English vowel:
|
|
<programlisting>
|
|
$[*] ? (@ like_regex "^[aeiou]" flag "i")
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The optional <literal>flag</literal> string may include one or more of
|
|
the characters
|
|
<literal>i</literal> for case-insensitive match,
|
|
<literal>m</literal> to allow <literal>^</literal>
|
|
and <literal>$</literal> to match at newlines,
|
|
<literal>s</literal> to allow <literal>.</literal> to match a newline,
|
|
and <literal>q</literal> to quote the whole pattern (reducing the
|
|
behavior to a simple substring match).
|
|
</para>
|
|
|
|
<para>
|
|
The SQL/JSON standard borrows its definition for regular expressions
|
|
from the <literal>LIKE_REGEX</literal> operator, which in turn uses the
|
|
XQuery standard. PostgreSQL does not currently support the
|
|
<literal>LIKE_REGEX</literal> operator. Therefore,
|
|
the <literal>like_regex</literal> filter is implemented using the
|
|
POSIX regular expression engine described in
|
|
<xref linkend="functions-posix-regexp"/>. This leads to various minor
|
|
discrepancies from standard SQL/JSON behavior, which are cataloged in
|
|
<xref linkend="posix-vs-xquery"/>.
|
|
Note, however, that the flag-letter incompatibilities described there
|
|
do not apply to SQL/JSON, as it translates the XQuery flag letters to
|
|
match what the POSIX engine expects.
|
|
</para>
|
|
|
|
<para>
|
|
Keep in mind that the pattern argument of <literal>like_regex</literal>
|
|
is a JSON path string literal, written according to the rules given in
|
|
<xref linkend="datatype-jsonpath"/>. This means in particular that any
|
|
backslashes you want to use in the regular expression must be doubled.
|
|
For example, to match string values of the root document that contain
|
|
only digits:
|
|
<programlisting>
|
|
$.* ? (@ like_regex "^\\d+$")
|
|
</programlisting>
|
|
</para>
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2 id="sqljson-query-functions">
|
|
<title>SQL/JSON Query Functions</title>
|
|
<para>
|
|
SQL/JSON functions <literal>JSON_EXISTS()</literal>,
|
|
<literal>JSON_QUERY()</literal>, and <literal>JSON_VALUE()</literal>
|
|
described in <xref linkend="functions-sqljson-querying"/> can be used
|
|
to query JSON documents. Each of these functions apply a
|
|
<replaceable>path_expression</replaceable> (the query) to a
|
|
<replaceable>context_item</replaceable> (the document); see
|
|
<xref linkend="functions-sqljson-path"/> for more details on what
|
|
<replaceable>path_expression</replaceable> can contain.
|
|
</para>
|
|
|
|
<table id="functions-sqljson-querying">
|
|
<title>SQL/JSON Query Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function signature
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm><primary>json_exists</primary></indexterm>
|
|
<function>json_exists</function> (
|
|
<replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable> <optional> <literal>PASSING</literal> { <replaceable>value</replaceable> <literal>AS</literal> <replaceable>varname</replaceable> } <optional>, ...</optional></optional>
|
|
<optional> { <literal>TRUE</literal> | <literal>FALSE</literal> |<literal> UNKNOWN</literal> | <literal>ERROR</literal> } <literal>ON ERROR</literal> </optional>)
|
|
</para>
|
|
<para>
|
|
Returns true if the SQL/JSON <replaceable>path_expression</replaceable>
|
|
applied to the <replaceable>context_item</replaceable> using the
|
|
<literal>PASSING</literal> <replaceable>value</replaceable>s yields any
|
|
items.
|
|
</para>
|
|
<para>
|
|
The <literal>ON ERROR</literal> clause specifies the behavior if
|
|
an error occurs; the default is to return the <type>boolean</type>
|
|
<literal>FALSE</literal> value. Note that if the
|
|
<replaceable>path_expression</replaceable> is <literal>strict</literal>
|
|
and <literal>ON ERROR</literal> behavior is <literal>ERROR</literal>,
|
|
an error is generated if it yields no items.
|
|
</para>
|
|
<para>
|
|
Examples:
|
|
</para>
|
|
<para>
|
|
<literal>select json_exists(jsonb '{"key1": [1,2,3]}', 'strict $.key1[*] ? (@ > 2)')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>select json_exists(jsonb '{"a": [1,2,3]}', 'lax $.a[5]' ERROR ON ERROR)</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>select json_exists(jsonb '{"a": [1,2,3]}', 'strict $.a[5]' ERROR ON ERROR)</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
ERROR: jsonpath array subscript is out of bounds
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm><primary>json_query</primary></indexterm>
|
|
<function>json_query</function> (
|
|
<replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable> <optional> <literal>PASSING</literal> { <replaceable>value</replaceable> <literal>AS</literal> <replaceable>varname</replaceable> } <optional>, ...</optional></optional>
|
|
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>
|
|
<optional> { <literal>WITHOUT</literal> | <literal>WITH</literal> { <literal>CONDITIONAL</literal> | <optional><literal>UNCONDITIONAL</literal></optional> } } <optional> <literal>ARRAY</literal> </optional> <literal>WRAPPER</literal> </optional>
|
|
<optional> { <literal>KEEP</literal> | <literal>OMIT</literal> } <literal>QUOTES</literal> <optional> <literal>ON SCALAR STRING</literal> </optional> </optional>
|
|
<optional> { <literal>ERROR</literal> | <literal>NULL</literal> | <literal>EMPTY</literal> { <optional> <literal>ARRAY</literal> </optional> | <literal>OBJECT</literal> } | <literal>DEFAULT</literal> <replaceable>expression</replaceable> } <literal>ON EMPTY</literal> </optional>
|
|
<optional> { <literal>ERROR</literal> | <literal>NULL</literal> | <literal>EMPTY</literal> { <optional> <literal>ARRAY</literal> </optional> | <literal>OBJECT</literal> } | <literal>DEFAULT</literal> <replaceable>expression</replaceable> } <literal>ON ERROR</literal> </optional>)
|
|
</para>
|
|
<para>
|
|
Returns the result of applying the SQL/JSON
|
|
<replaceable>path_expression</replaceable> to the
|
|
<replaceable>context_item</replaceable> using the
|
|
<literal>PASSING</literal> <replaceable>value</replaceable>s.
|
|
</para>
|
|
<para>
|
|
If the path expression returns multiple SQL/JSON items, it might be
|
|
necessary to wrap the result using the <literal>WITH WRAPPER</literal>
|
|
clause to make it a valid JSON string. If the wrapper is
|
|
<literal>UNCONDITIONAL</literal>, an array wrapper will always be
|
|
applied, even if the returned value is already a single JSON object
|
|
or an array. If it is <literal>CONDITIONAL</literal>, it will not be
|
|
applied to a single JSON object or an array.
|
|
<literal>UNCONDITIONAL</literal> is the default.
|
|
</para>
|
|
<para>
|
|
If the result is a scalar string, by default, the returned value will
|
|
be surrounded by quotes, making it a valid JSON value. It can be made
|
|
explicit by specifying <literal>KEEP QUOTES</literal>. Conversely,
|
|
quotes can be omitted by specifying <literal>OMIT QUOTES</literal>.
|
|
Note that <literal>OMIT QUOTES</literal> cannot be specified when
|
|
<literal>WITH WRAPPER</literal> is also specified.
|
|
</para>
|
|
<para>
|
|
The <literal>RETURNING</literal> clause can be used to specify the
|
|
<replaceable>data_type</replaceable> of the result value. By default,
|
|
the returned value will be of type <type>jsonb</type>.
|
|
</para>
|
|
<para>
|
|
The <literal>ON EMPTY</literal> clause specifies the behavior if
|
|
evaluating <replaceable>path_expression</replaceable> yields no value
|
|
at all. The default when <literal>ON EMPTY</literal> is not specified
|
|
is to return a null value.
|
|
</para>
|
|
<para>
|
|
The <literal>ON ERROR</literal> clause specifies the
|
|
behavior if an error occurs when evaluating
|
|
<replaceable>path_expression</replaceable>, including the operation to
|
|
coerce the result value to the output type, or during the execution of
|
|
<literal>ON EMPTY</literal> behavior (that is caused by empty result
|
|
of <replaceable>path_expression</replaceable> evaluation). The default
|
|
when <literal>ON ERROR</literal> is not specified is to return a null
|
|
value.
|
|
</para>
|
|
<para>
|
|
Examples:
|
|
</para>
|
|
<para>
|
|
<literal>select json_query(jsonb '[1,[2,3],null]', 'lax $[*][1]' WITH CONDITIONAL WRAPPER)</literal>
|
|
<returnvalue>[3]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>select json_query(jsonb '{"a": "[1, 2]"}', 'lax $.a' OMIT QUOTES);</literal>
|
|
<returnvalue>[1, 2]</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>select json_query(jsonb '{"a": "[1, 2]"}', 'lax $.a' RETURNING int[] OMIT QUOTES ERROR ON ERROR);</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
ERROR: malformed array literal: "[1, 2]"
|
|
DETAIL: Missing "]" after array dimensions.
|
|
</programlisting>
|
|
</para>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm><primary>json_value</primary></indexterm>
|
|
<function>json_value</function> (
|
|
<replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable>
|
|
<optional> <literal>PASSING</literal> { <replaceable>value</replaceable> <literal>AS</literal> <replaceable>varname</replaceable> } <optional>, ...</optional></optional>
|
|
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> </optional>
|
|
<optional> { <literal>ERROR</literal> | <literal>NULL</literal> | <literal>DEFAULT</literal> <replaceable>expression</replaceable> } <literal>ON EMPTY</literal> </optional>
|
|
<optional> { <literal>ERROR</literal> | <literal>NULL</literal> | <literal>DEFAULT</literal> <replaceable>expression</replaceable> } <literal>ON ERROR</literal> </optional>)
|
|
</para>
|
|
<para>
|
|
Returns the result of applying the SQL/JSON
|
|
<replaceable>path_expression</replaceable> to the
|
|
<replaceable>context_item</replaceable> using the
|
|
<literal>PASSING</literal> <replaceable>value</replaceable>s.
|
|
</para>
|
|
<para>
|
|
The extracted value must be a single <acronym>SQL/JSON</acronym>
|
|
scalar item; an error is thrown if that's not the case. If you expect
|
|
that extracted value might be an object or an array, use the
|
|
<function>json_query</function> function instead.
|
|
</para>
|
|
<para>
|
|
The <literal>RETURNING</literal> clause can be used to specify the
|
|
<replaceable>data_type</replaceable> of the result value. By default,
|
|
the returned value will be of type <type>text</type>.
|
|
</para>
|
|
<para>
|
|
The <literal>ON ERROR</literal> and <literal>ON EMPTY</literal>
|
|
clauses have similar semantics as mentioned in the description of
|
|
<function>json_query</function>.
|
|
</para>
|
|
<para>
|
|
Note that scalar strings returned by <function>json_value</function>
|
|
always have their quotes removed, equivalent to specifying
|
|
<literal>OMIT QUOTES</literal> in <function>json_query</function>.
|
|
</para>
|
|
<para>
|
|
Examples:
|
|
</para>
|
|
<para>
|
|
<literal>select json_value(jsonb '"123.45"', '$' RETURNING float)</literal>
|
|
<returnvalue>123.45</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>select json_value(jsonb '"03:04 2015-02-01"', '$.datetime("HH24:MI YYYY-MM-DD")' RETURNING date)</literal>
|
|
<returnvalue>2015-02-01</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>select json_value(jsonb '[1,2]', 'strict $[*]' DEFAULT 9 ON ERROR)</literal>
|
|
<returnvalue>9</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-sqljson-table">
|
|
<title>JSON_TABLE</title>
|
|
<indexterm>
|
|
<primary>json_table</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<function>JSON_TABLE</function> is an SQL/JSON function which
|
|
queries <acronym>JSON</acronym> data
|
|
and presents the results as a relational view, which can be accessed as a
|
|
regular SQL table. You can use <function>JSON_TABLE</function> inside
|
|
the <literal>FROM</literal> clause of a <literal>SELECT</literal>,
|
|
<literal>UPDATE</literal>, or <literal>DELETE</literal> and as data source
|
|
in a <literal>MERGE</literal> statement.
|
|
</para>
|
|
|
|
<para>
|
|
Taking JSON data as input, <function>JSON_TABLE</function> uses a JSON path
|
|
expression to extract a part of the provided data to use as a
|
|
<firstterm>row pattern</firstterm> for the constructed view. Each SQL/JSON
|
|
value given by the row pattern serves as source for a separate row in the
|
|
constructed view.
|
|
</para>
|
|
|
|
<para>
|
|
To split the row pattern into columns, <function>JSON_TABLE</function>
|
|
provides the <literal>COLUMNS</literal> clause that defines the
|
|
schema of the created view. For each column, a separate JSON path expression
|
|
can be specified to be evaluated against the row pattern to get an SQL/JSON
|
|
value that will become the value for the specified column in a given output
|
|
row.
|
|
</para>
|
|
|
|
<para>
|
|
JSON data stored at a nested level of the row pattern can be extracted using
|
|
the <literal>NESTED PATH</literal> clause. Each
|
|
<literal>NESTED PATH</literal> clause can be used to generate one or more
|
|
columns using the data from a nested level of the row pattern. Those
|
|
columns can be specified using a <literal>COLUMNS</literal> clause that
|
|
looks similar to the top-level COLUMNS clause. Rows constructed from
|
|
NESTED COLUMNS are called <firstterm>child rows</firstterm> and are joined
|
|
against the row constructed from the columns specified in the parent
|
|
<literal>COLUMNS</literal> clause to get the row in the final view. Child
|
|
columns themselves may contain a <literal>NESTED PATH</literal>
|
|
specification thus allowing to extract data located at arbitrary nesting
|
|
levels. Columns produced by multiple <literal>NESTED PATH</literal>s at the
|
|
same level are considered to be <firstterm>siblings</firstterm> of each
|
|
other and their rows after joining with the parent row are combined using
|
|
UNION.
|
|
</para>
|
|
|
|
<para>
|
|
The rows produced by <function>JSON_TABLE</function> are laterally
|
|
joined to the row that generated them, so you do not have to explicitly join
|
|
the constructed view with the original table holding <acronym>JSON</acronym>
|
|
data.
|
|
</para>
|
|
|
|
<para>
|
|
The syntax is:
|
|
</para>
|
|
|
|
<synopsis>
|
|
JSON_TABLE (
|
|
<replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable> <optional> AS <replaceable>json_path_name</replaceable> </optional> <optional> PASSING { <replaceable>value</replaceable> AS <replaceable>varname</replaceable> } <optional>, ...</optional> </optional>
|
|
COLUMNS ( <replaceable class="parameter">json_table_column</replaceable> <optional>, ...</optional> )
|
|
<optional> { <literal>ERROR</literal> | <literal>EMPTY</literal> } <literal>ON ERROR</literal> </optional>
|
|
)
|
|
|
|
<phrase>
|
|
where <replaceable class="parameter">json_table_column</replaceable> is:
|
|
</phrase>
|
|
<replaceable>name</replaceable> FOR ORDINALITY
|
|
| <replaceable>name</replaceable> <replaceable>type</replaceable>
|
|
<optional> FORMAT JSON <optional>ENCODING <literal>UTF8</literal></optional></optional>
|
|
<optional> PATH <replaceable>path_expression</replaceable> </optional>
|
|
<optional> { WITHOUT | WITH { CONDITIONAL | <optional>UNCONDITIONAL</optional> } } <optional> ARRAY </optional> WRAPPER </optional>
|
|
<optional> { KEEP | OMIT } QUOTES <optional> ON SCALAR STRING </optional> </optional>
|
|
<optional> { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT <replaceable>expression</replaceable> } ON EMPTY </optional>
|
|
<optional> { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT <replaceable>expression</replaceable> } ON ERROR </optional>
|
|
| <replaceable>name</replaceable> <replaceable>type</replaceable> EXISTS <optional> PATH <replaceable>path_expression</replaceable> </optional>
|
|
<optional> { ERROR | TRUE | FALSE | UNKNOWN } ON ERROR </optional>
|
|
| NESTED <optional> PATH </optional> <replaceable>path_expression</replaceable> <optional> AS <replaceable>json_path_name</replaceable> </optional> COLUMNS ( <replaceable>json_table_column</replaceable> <optional>, ...</optional> )
|
|
</synopsis>
|
|
|
|
<para>
|
|
Each syntax element is described below in more detail.
|
|
</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>
|
|
<literal><replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable> <optional> <literal>AS</literal> <replaceable>json_path_name</replaceable> </optional> <optional> <literal>PASSING</literal> { <replaceable>value</replaceable> <literal>AS</literal> <replaceable>varname</replaceable> } <optional>, ...</optional></optional></literal>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
The input data to query (<replaceable>context_item</replaceable>),
|
|
the JSON path expression defining the query (<replaceable>path_expression</replaceable>)
|
|
with an optional name (<replaceable>json_path_name</replaceable>), and an
|
|
optional <literal>PASSING</literal> clause, which can provide data values
|
|
to the <replaceable>path_expression</replaceable>. The result of the input
|
|
data evaluation using the aforementioned elements is called the
|
|
<firstterm>row pattern</firstterm>, which is used as the source for row
|
|
values in the constructed view.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<literal>COLUMNS</literal> ( <replaceable>json_table_column</replaceable> <optional>, ...</optional> )
|
|
</term>
|
|
<listitem>
|
|
|
|
<para>
|
|
The <literal>COLUMNS</literal> clause defining the schema of the
|
|
constructed view. In this clause, you can specify each column to be
|
|
filled with an SQL/JSON value obtained by applying a JSON path expression
|
|
against the row pattern. <replaceable>json_table_column</replaceable> has
|
|
the following variants:
|
|
</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>
|
|
<replaceable>name</replaceable> <literal>FOR ORDINALITY</literal>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Adds an ordinality column that provides sequential row numbering starting
|
|
from 1. Each <literal>NESTED PATH</literal> (see below) gets its own
|
|
counter for any nested ordinality columns.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<literal><replaceable>name</replaceable> <replaceable>type</replaceable>
|
|
<optional><literal>FORMAT JSON</literal> <optional>ENCODING <literal>UTF8</literal></optional></optional>
|
|
<optional> <literal>PATH</literal> <replaceable>path_expression</replaceable> </optional></literal>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Inserts an SQL/JSON value obtained by applying
|
|
<replaceable>path_expression</replaceable> against the row pattern into
|
|
the view's output row after coercing it to specified
|
|
<replaceable>type</replaceable>.
|
|
</para>
|
|
<para>
|
|
Specifying <literal>FORMAT JSON</literal> makes it explicit that you
|
|
expect the value to be a valid <type>json</type> object. It only
|
|
makes sense to specify <literal>FORMAT JSON</literal> if
|
|
<replaceable>type</replaceable> is one of <type>bpchar</type>,
|
|
<type>bytea</type>, <type>character varying</type>, <type>name</type>,
|
|
<type>json</type>, <type>jsonb</type>, <type>text</type>, or a domain over
|
|
these types.
|
|
</para>
|
|
<para>
|
|
Optionally, you can specify <literal>WRAPPER</literal> and
|
|
<literal>QUOTES</literal> clauses to format the output. Note that
|
|
specifying <literal>OMIT QUOTES</literal> overrides
|
|
<literal>FORMAT JSON</literal> if also specified, because unquoted
|
|
literals do not constitute valid <type>json</type> values.
|
|
</para>
|
|
<para>
|
|
Optionally, you can use <literal>ON EMPTY</literal> and
|
|
<literal>ON ERROR</literal> clauses to specify whether to throw the error
|
|
or return the specified value when the result of JSON path evaluation is
|
|
empty and when an error occurs during JSON path evaluation or when
|
|
coercing the SQL/JSON value to the specified type, respectively. The
|
|
default for both is to return a <literal>NULL</literal> value.
|
|
</para>
|
|
<note>
|
|
<para>
|
|
This clause is internally turned into and has the same semantics as
|
|
<function>JSON_VALUE</function> or <function>JSON_QUERY</function>.
|
|
The latter if the specified type is not a scalar type or if either of
|
|
<literal>FORMAT JSON</literal>, <literal>WRAPPER</literal>, or
|
|
<literal>QUOTES</literal> clause is present.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<replaceable>name</replaceable> <replaceable>type</replaceable>
|
|
<literal>EXISTS</literal> <optional> <literal>PATH</literal> <replaceable>path_expression</replaceable> </optional>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
Inserts a boolean value obtained by applying
|
|
<replaceable>path_expression</replaceable> against the row pattern
|
|
into the view's output row after coercing it to specified
|
|
<replaceable>type</replaceable>.
|
|
</para>
|
|
<para>
|
|
The value corresponds to whether applying the <literal>PATH</literal>
|
|
expression to the row pattern yields any values.
|
|
</para>
|
|
<para>
|
|
The specified <replaceable>type</replaceable> should have a cast from the
|
|
<type>boolean</type> type.
|
|
</para>
|
|
<para>
|
|
Optionally, you can use <literal>ON ERROR</literal> to specify whether to
|
|
throw the error or return the specified value when an error occurs during
|
|
JSON path evaluation or when coercing SQL/JSON value to the specified
|
|
type. The default is to return a boolean value
|
|
<literal>FALSE</literal>.
|
|
</para>
|
|
<note>
|
|
<para>
|
|
This clause is internally turned into and has the same semantics as
|
|
<function>JSON_EXISTS</function>.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<literal>NESTED <optional> PATH </optional></literal> <replaceable>path_expression</replaceable> <optional> <literal>AS</literal> <replaceable>json_path_name</replaceable> </optional>
|
|
<literal>COLUMNS</literal> ( <replaceable>json_table_column</replaceable> <optional>, ...</optional> )
|
|
</term>
|
|
<listitem>
|
|
|
|
<para>
|
|
Extracts SQL/JSON values from nested levels of the row pattern,
|
|
generates one or more columns as defined by the <literal>COLUMNS</literal>
|
|
subclause, and inserts the extracted SQL/JSON values into those
|
|
columns. The <replaceable>json_table_column</replaceable>
|
|
expression in the <literal>COLUMNS</literal> subclause uses the same
|
|
syntax as in the parent <literal>COLUMNS</literal> clause.
|
|
</para>
|
|
|
|
<para>
|
|
The <literal>NESTED PATH</literal> syntax is recursive,
|
|
so you can go down multiple nested levels by specifying several
|
|
<literal>NESTED PATH</literal> subclauses within each other.
|
|
It allows to unnest the hierarchy of JSON objects and arrays
|
|
in a single function invocation rather than chaining several
|
|
<function>JSON_TABLE</function> expressions in an SQL statement.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<note>
|
|
<para>
|
|
In each variant of <replaceable>json_table_column</replaceable> described
|
|
above, if the <literal>PATH</literal> clause is omitted, path expression
|
|
<literal>$.<replaceable>name</replaceable></literal> is used, where
|
|
<replaceable>name</replaceable> is the provided column name.
|
|
</para>
|
|
</note>
|
|
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<literal>AS</literal> <replaceable>json_path_name</replaceable>
|
|
</term>
|
|
<listitem>
|
|
|
|
<para>
|
|
The optional <replaceable>json_path_name</replaceable> serves as an
|
|
identifier of the provided <replaceable>path_expression</replaceable>.
|
|
The name must be unique and distinct from the column names.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
{ <literal>ERROR</literal> | <literal>EMPTY</literal> } <literal>ON ERROR</literal>
|
|
</term>
|
|
<listitem>
|
|
|
|
<para>
|
|
The optional <literal>ON ERROR</literal> can be used to specify how to
|
|
handle errors when evaluating the top-level
|
|
<replaceable>path_expression</replaceable>. Use <literal>ERROR</literal>
|
|
if you want the errors to be thrown and <literal>EMPTY</literal> to
|
|
return an empty table, that is, a table containing 0 rows. Note that
|
|
this clause does not affect the errors that occur when evaluating
|
|
columns, for which the behavior depends on whether the
|
|
<literal>ON ERROR</literal> clause is specified against a given column.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>Examples</para>
|
|
|
|
<para>
|
|
In the examples that follow, the following table containing JSON data
|
|
will be used:
|
|
|
|
<programlisting>
|
|
CREATE TABLE my_films ( js jsonb );
|
|
|
|
INSERT INTO my_films VALUES (
|
|
'{ "favorites" : [
|
|
{ "kind" : "comedy", "films" : [
|
|
{ "title" : "Bananas",
|
|
"director" : "Woody Allen"},
|
|
{ "title" : "The Dinner Game",
|
|
"director" : "Francis Veber" } ] },
|
|
{ "kind" : "horror", "films" : [
|
|
{ "title" : "Psycho",
|
|
"director" : "Alfred Hitchcock" } ] },
|
|
{ "kind" : "thriller", "films" : [
|
|
{ "title" : "Vertigo",
|
|
"director" : "Alfred Hitchcock" } ] },
|
|
{ "kind" : "drama", "films" : [
|
|
{ "title" : "Yojimbo",
|
|
"director" : "Akira Kurosawa" } ] }
|
|
] }');
|
|
</programlisting>
|
|
|
|
</para>
|
|
<para>
|
|
The following query shows how to use <function>JSON_TABLE</function> to
|
|
turn the JSON objects in the <structname>my_films</structname> table
|
|
to a view containing columns for the keys <literal>kind</literal>,
|
|
<literal>title</literal>, and <literal>director</literal> contained in
|
|
the original JSON along with an ordinality column:
|
|
|
|
<programlisting>
|
|
SELECT jt.* FROM
|
|
my_films,
|
|
JSON_TABLE (js, '$.favorites[*]' COLUMNS (
|
|
id FOR ORDINALITY,
|
|
kind text PATH '$.kind',
|
|
title text PATH '$.films[*].title' WITH WRAPPER,
|
|
director text PATH '$.films[*].director' WITH WRAPPER)) AS jt;
|
|
</programlisting>
|
|
|
|
<screen>
|
|
id | kind | title | director
|
|
----+----------+--------------------------------+----------------------------------
|
|
1 | comedy | ["Bananas", "The Dinner Game"] | ["Woody Allen", "Francis Veber"]
|
|
2 | horror | ["Psycho"] | ["Alfred Hitchcock"]
|
|
3 | thriller | ["Vertigo"] | ["Alfred Hitchcock"]
|
|
4 | drama | ["Yojimbo"] | ["Akira Kurosawa"]
|
|
(4 rows)
|
|
</screen>
|
|
|
|
</para>
|
|
<para>
|
|
The following is a modified version of the above query to show the
|
|
usage of <literal>PASSING</literal> arguments in the filter specified in
|
|
the top-level JSON path expression and the various options for the
|
|
individual columns:
|
|
|
|
<programlisting>
|
|
SELECT jt.* FROM
|
|
my_films,
|
|
JSON_TABLE (js, '$.favorites[*] ? (@.films[*].director == $filter)'
|
|
PASSING 'Alfred Hitchcock' AS filter, 'Vertigo' AS filter2
|
|
COLUMNS (
|
|
id FOR ORDINALITY,
|
|
kind text PATH '$.kind',
|
|
title text FORMAT JSON PATH '$.films[*].title' OMIT QUOTES,
|
|
director text PATH '$.films[*].director' KEEP QUOTES)) AS jt;
|
|
</programlisting>
|
|
|
|
<screen>
|
|
id | kind | title | director
|
|
----+----------+---------+--------------------
|
|
1 | horror | Psycho | "Alfred Hitchcock"
|
|
2 | thriller | Vertigo | "Alfred Hitchcock"
|
|
(2 rows)
|
|
</screen>
|
|
|
|
</para>
|
|
<para>
|
|
The following is a modified version of the above query to show the usage
|
|
of <literal>NESTED PATH</literal> for populating title and director
|
|
columns, illustrating how they are joined to the parent columns id and
|
|
kind:
|
|
|
|
<programlisting>
|
|
SELECT jt.* FROM
|
|
my_films,
|
|
JSON_TABLE ( js, '$.favorites[*] ? (@.films[*].director == $filter)'
|
|
PASSING 'Alfred Hitchcock' AS filter
|
|
COLUMNS (
|
|
id FOR ORDINALITY,
|
|
kind text PATH '$.kind',
|
|
NESTED PATH '$.films[*]' COLUMNS (
|
|
title text FORMAT JSON PATH '$.title' OMIT QUOTES,
|
|
director text PATH '$.director' KEEP QUOTES))) AS jt;
|
|
</programlisting>
|
|
|
|
<screen>
|
|
id | kind | title | director
|
|
----+----------+---------+--------------------
|
|
1 | horror | Psycho | "Alfred Hitchcock"
|
|
2 | thriller | Vertigo | "Alfred Hitchcock"
|
|
(2 rows)
|
|
</screen>
|
|
|
|
</para>
|
|
|
|
<para>
|
|
The following is the same query but without the filter in the root
|
|
path:
|
|
|
|
<programlisting>
|
|
SELECT jt.* FROM
|
|
my_films,
|
|
JSON_TABLE ( js, '$.favorites[*]'
|
|
COLUMNS (
|
|
id FOR ORDINALITY,
|
|
kind text PATH '$.kind',
|
|
NESTED PATH '$.films[*]' COLUMNS (
|
|
title text FORMAT JSON PATH '$.title' OMIT QUOTES,
|
|
director text PATH '$.director' KEEP QUOTES))) AS jt;
|
|
</programlisting>
|
|
|
|
<screen>
|
|
id | kind | title | director
|
|
----+----------+-----------------+--------------------
|
|
1 | comedy | Bananas | "Woody Allen"
|
|
1 | comedy | The Dinner Game | "Francis Veber"
|
|
2 | horror | Psycho | "Alfred Hitchcock"
|
|
3 | thriller | Vertigo | "Alfred Hitchcock"
|
|
4 | drama | Yojimbo | "Akira Kurosawa"
|
|
(5 rows)
|
|
</screen>
|
|
|
|
</para>
|
|
|
|
<para>
|
|
The following shows another query using a different <type>JSON</type>
|
|
object as input. It shows the UNION "sibling join" between
|
|
<literal>NESTED</literal> paths <literal>$.movies[*]</literal> and
|
|
<literal>$.books[*]</literal> and also the usage of
|
|
<literal>FOR ORDINALITY</literal> column at <literal>NESTED</literal>
|
|
levels (columns <literal>movie_id</literal>, <literal>book_id</literal>,
|
|
and <literal>author_id</literal>):
|
|
|
|
<programlisting>
|
|
SELECT * FROM JSON_TABLE (
|
|
'{"favorites":
|
|
{"movies":
|
|
[{"name": "One", "director": "John Doe"},
|
|
{"name": "Two", "director": "Don Joe"}],
|
|
"books":
|
|
[{"name": "Mystery", "authors": [{"name": "Brown Dan"}]},
|
|
{"name": "Wonder", "authors": [{"name": "Jun Murakami"}, {"name":"Craig Doe"}]}]
|
|
}}'::json, '$.favorites[*]'
|
|
COLUMNS (
|
|
user_id FOR ORDINALITY,
|
|
NESTED '$.movies[*]'
|
|
COLUMNS (
|
|
movie_id FOR ORDINALITY,
|
|
mname text PATH '$.name',
|
|
director text),
|
|
NESTED '$.books[*]'
|
|
COLUMNS (
|
|
book_id FOR ORDINALITY,
|
|
bname text PATH '$.name',
|
|
NESTED '$.authors[*]'
|
|
COLUMNS (
|
|
author_id FOR ORDINALITY,
|
|
author_name text PATH '$.name'))));
|
|
</programlisting>
|
|
|
|
<screen>
|
|
user_id | movie_id | mname | director | book_id | bname | author_id | author_name
|
|
---------+----------+-------+----------+---------+---------+-----------+--------------
|
|
1 | 1 | One | John Doe | | | |
|
|
1 | 2 | Two | Don Joe | | | |
|
|
1 | | | | 1 | Mystery | 1 | Brown Dan
|
|
1 | | | | 2 | Wonder | 1 | Jun Murakami
|
|
1 | | | | 2 | Wonder | 2 | Craig Doe
|
|
(5 rows)
|
|
</screen>
|
|
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-sequence">
|
|
<title>Sequence Manipulation Functions</title>
|
|
|
|
<indexterm>
|
|
<primary>sequence</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
This section describes functions for operating on <firstterm>sequence
|
|
objects</firstterm>, also called sequence generators or just sequences.
|
|
Sequence objects are special single-row tables created with <xref
|
|
linkend="sql-createsequence"/>.
|
|
Sequence objects are commonly used to generate unique identifiers
|
|
for rows of a table. The sequence functions, listed in <xref
|
|
linkend="functions-sequence-table"/>, provide simple, multiuser-safe
|
|
methods for obtaining successive sequence values from sequence
|
|
objects.
|
|
</para>
|
|
|
|
<table id="functions-sequence-table">
|
|
<title>Sequence Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>nextval</primary>
|
|
</indexterm>
|
|
<function>nextval</function> ( <type>regclass</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Advances the sequence object to its next value and returns that value.
|
|
This is done atomically: even if multiple sessions
|
|
execute <function>nextval</function> concurrently, each will safely
|
|
receive a distinct sequence value.
|
|
If the sequence object has been created with default parameters,
|
|
successive <function>nextval</function> calls will return successive
|
|
values beginning with 1. Other behaviors can be obtained by using
|
|
appropriate parameters in the <xref linkend="sql-createsequence"/>
|
|
command.
|
|
</para>
|
|
<para>
|
|
This function requires <literal>USAGE</literal>
|
|
or <literal>UPDATE</literal> privilege on the sequence.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>setval</primary>
|
|
</indexterm>
|
|
<function>setval</function> ( <type>regclass</type>, <type>bigint</type> <optional>, <type>boolean</type> </optional> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets the sequence object's current value, and optionally
|
|
its <literal>is_called</literal> flag. The two-parameter
|
|
form sets the sequence's <literal>last_value</literal> field to the
|
|
specified value and sets its <literal>is_called</literal> field to
|
|
<literal>true</literal>, meaning that the next
|
|
<function>nextval</function> will advance the sequence before
|
|
returning a value. The value that will be reported
|
|
by <function>currval</function> is also set to the specified value.
|
|
In the three-parameter form, <literal>is_called</literal> can be set
|
|
to either <literal>true</literal>
|
|
or <literal>false</literal>. <literal>true</literal> has the same
|
|
effect as the two-parameter form. If it is set
|
|
to <literal>false</literal>, the next <function>nextval</function>
|
|
will return exactly the specified value, and sequence advancement
|
|
commences with the following <function>nextval</function>.
|
|
Furthermore, the value reported by <function>currval</function> is not
|
|
changed in this case. For example,
|
|
<programlisting>
|
|
SELECT setval('myseq', 42); <lineannotation>Next <function>nextval</function> will return 43</lineannotation>
|
|
SELECT setval('myseq', 42, true); <lineannotation>Same as above</lineannotation>
|
|
SELECT setval('myseq', 42, false); <lineannotation>Next <function>nextval</function> will return 42</lineannotation>
|
|
</programlisting>
|
|
The result returned by <function>setval</function> is just the value of its
|
|
second argument.
|
|
</para>
|
|
<para>
|
|
This function requires <literal>UPDATE</literal> privilege on the
|
|
sequence.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>currval</primary>
|
|
</indexterm>
|
|
<function>currval</function> ( <type>regclass</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the value most recently obtained
|
|
by <function>nextval</function> for this sequence in the current
|
|
session. (An error is reported if <function>nextval</function> has
|
|
never been called for this sequence in this session.) Because this is
|
|
returning a session-local value, it gives a predictable answer whether
|
|
or not other sessions have executed <function>nextval</function> since
|
|
the current session did.
|
|
</para>
|
|
<para>
|
|
This function requires <literal>USAGE</literal>
|
|
or <literal>SELECT</literal> privilege on the sequence.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lastval</primary>
|
|
</indexterm>
|
|
<function>lastval</function> ()
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the value most recently returned by
|
|
<function>nextval</function> in the current session. This function is
|
|
identical to <function>currval</function>, except that instead
|
|
of taking the sequence name as an argument it refers to whichever
|
|
sequence <function>nextval</function> was most recently applied to
|
|
in the current session. It is an error to call
|
|
<function>lastval</function> if <function>nextval</function>
|
|
has not yet been called in the current session.
|
|
</para>
|
|
<para>
|
|
This function requires <literal>USAGE</literal>
|
|
or <literal>SELECT</literal> privilege on the last used sequence.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<caution>
|
|
<para>
|
|
To avoid blocking concurrent transactions that obtain numbers from
|
|
the same sequence, the value obtained by <function>nextval</function>
|
|
is not reclaimed for re-use if the calling transaction later aborts.
|
|
This means that transaction aborts or database crashes can result in
|
|
gaps in the sequence of assigned values. That can happen without a
|
|
transaction abort, too. For example an <command>INSERT</command> with
|
|
an <literal>ON CONFLICT</literal> clause will compute the to-be-inserted
|
|
tuple, including doing any required <function>nextval</function>
|
|
calls, before detecting any conflict that would cause it to follow
|
|
the <literal>ON CONFLICT</literal> rule instead.
|
|
Thus, <productname>PostgreSQL</productname> sequence
|
|
objects <emphasis>cannot be used to obtain <quote>gapless</quote>
|
|
sequences</emphasis>.
|
|
</para>
|
|
|
|
<para>
|
|
Likewise, sequence state changes made by <function>setval</function>
|
|
are immediately visible to other transactions, and are not undone if
|
|
the calling transaction rolls back.
|
|
</para>
|
|
|
|
<para>
|
|
If the database cluster crashes before committing a transaction
|
|
containing a <function>nextval</function>
|
|
or <function>setval</function> call, the sequence state change might
|
|
not have made its way to persistent storage, so that it is uncertain
|
|
whether the sequence will have its original or updated state after the
|
|
cluster restarts. This is harmless for usage of the sequence within
|
|
the database, since other effects of uncommitted transactions will not
|
|
be visible either. However, if you wish to use a sequence value for
|
|
persistent outside-the-database purposes, make sure that the
|
|
<function>nextval</function> call has been committed before doing so.
|
|
</para>
|
|
</caution>
|
|
|
|
<para>
|
|
The sequence to be operated on by a sequence function is specified by
|
|
a <type>regclass</type> argument, which is simply the OID of the sequence in the
|
|
<structname>pg_class</structname> system catalog. You do not have to look up the
|
|
OID by hand, however, since the <type>regclass</type> data type's input
|
|
converter will do the work for you. See <xref linkend="datatype-oid"/>
|
|
for details.
|
|
</para>
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-conditional">
|
|
<title>Conditional Expressions</title>
|
|
|
|
<indexterm>
|
|
<primary>CASE</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>conditional expression</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
This section describes the <acronym>SQL</acronym>-compliant conditional expressions
|
|
available in <productname>PostgreSQL</productname>.
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
If your needs go beyond the capabilities of these conditional
|
|
expressions, you might want to consider writing a server-side function
|
|
in a more expressive programming language.
|
|
</para>
|
|
</tip>
|
|
|
|
<note>
|
|
<para>
|
|
Although <token>COALESCE</token>, <token>GREATEST</token>, and
|
|
<token>LEAST</token> are syntactically similar to functions, they are
|
|
not ordinary functions, and thus cannot be used with explicit
|
|
<token>VARIADIC</token> array arguments.
|
|
</para>
|
|
</note>
|
|
|
|
<sect2 id="functions-case">
|
|
<title><literal>CASE</literal></title>
|
|
|
|
<para>
|
|
The <acronym>SQL</acronym> <token>CASE</token> expression is a
|
|
generic conditional expression, similar to if/else statements in
|
|
other programming languages:
|
|
|
|
<synopsis>
|
|
CASE WHEN <replaceable>condition</replaceable> THEN <replaceable>result</replaceable>
|
|
<optional>WHEN ...</optional>
|
|
<optional>ELSE <replaceable>result</replaceable></optional>
|
|
END
|
|
</synopsis>
|
|
|
|
<token>CASE</token> clauses can be used wherever
|
|
an expression is valid. Each <replaceable>condition</replaceable> is an
|
|
expression that returns a <type>boolean</type> result. If the condition's
|
|
result is true, the value of the <token>CASE</token> expression is the
|
|
<replaceable>result</replaceable> that follows the condition, and the
|
|
remainder of the <token>CASE</token> expression is not processed. If the
|
|
condition's result is not true, any subsequent <token>WHEN</token> clauses
|
|
are examined in the same manner. If no <token>WHEN</token>
|
|
<replaceable>condition</replaceable> yields true, the value of the
|
|
<token>CASE</token> expression is the <replaceable>result</replaceable> of the
|
|
<token>ELSE</token> clause. If the <token>ELSE</token> clause is
|
|
omitted and no condition is true, the result is null.
|
|
</para>
|
|
|
|
<para>
|
|
An example:
|
|
<screen>
|
|
SELECT * FROM test;
|
|
|
|
a
|
|
---
|
|
1
|
|
2
|
|
3
|
|
|
|
|
|
SELECT a,
|
|
CASE WHEN a=1 THEN 'one'
|
|
WHEN a=2 THEN 'two'
|
|
ELSE 'other'
|
|
END
|
|
FROM test;
|
|
|
|
a | case
|
|
---+-------
|
|
1 | one
|
|
2 | two
|
|
3 | other
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
The data types of all the <replaceable>result</replaceable>
|
|
expressions must be convertible to a single output type.
|
|
See <xref linkend="typeconv-union-case"/> for more details.
|
|
</para>
|
|
|
|
<para>
|
|
There is a <quote>simple</quote> form of <token>CASE</token> expression
|
|
that is a variant of the general form above:
|
|
|
|
<synopsis>
|
|
CASE <replaceable>expression</replaceable>
|
|
WHEN <replaceable>value</replaceable> THEN <replaceable>result</replaceable>
|
|
<optional>WHEN ...</optional>
|
|
<optional>ELSE <replaceable>result</replaceable></optional>
|
|
END
|
|
</synopsis>
|
|
|
|
The first
|
|
<replaceable>expression</replaceable> is computed, then compared to
|
|
each of the <replaceable>value</replaceable> expressions in the
|
|
<token>WHEN</token> clauses until one is found that is equal to it. If
|
|
no match is found, the <replaceable>result</replaceable> of the
|
|
<token>ELSE</token> clause (or a null value) is returned. This is similar
|
|
to the <function>switch</function> statement in C.
|
|
</para>
|
|
|
|
<para>
|
|
The example above can be written using the simple
|
|
<token>CASE</token> syntax:
|
|
<screen>
|
|
SELECT a,
|
|
CASE a WHEN 1 THEN 'one'
|
|
WHEN 2 THEN 'two'
|
|
ELSE 'other'
|
|
END
|
|
FROM test;
|
|
|
|
a | case
|
|
---+-------
|
|
1 | one
|
|
2 | two
|
|
3 | other
|
|
</screen>
|
|
</para>
|
|
|
|
<para>
|
|
A <token>CASE</token> expression does not evaluate any subexpressions
|
|
that are not needed to determine the result. For example, this is a
|
|
possible way of avoiding a division-by-zero failure:
|
|
<programlisting>
|
|
SELECT ... WHERE CASE WHEN x <> 0 THEN y/x > 1.5 ELSE false END;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
As described in <xref linkend="syntax-express-eval"/>, there are various
|
|
situations in which subexpressions of an expression are evaluated at
|
|
different times, so that the principle that <quote><token>CASE</token>
|
|
evaluates only necessary subexpressions</quote> is not ironclad. For
|
|
example a constant <literal>1/0</literal> subexpression will usually result in
|
|
a division-by-zero failure at planning time, even if it's within
|
|
a <token>CASE</token> arm that would never be entered at run time.
|
|
</para>
|
|
</note>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-coalesce-nvl-ifnull">
|
|
<title><literal>COALESCE</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>COALESCE</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>NVL</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>IFNULL</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>COALESCE</function>(<replaceable>value</replaceable> <optional>, ...</optional>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>COALESCE</function> function returns the first of its
|
|
arguments that is not null. Null is returned only if all arguments
|
|
are null. It is often used to substitute a default value for
|
|
null values when data is retrieved for display, for example:
|
|
<programlisting>
|
|
SELECT COALESCE(description, short_description, '(none)') ...
|
|
</programlisting>
|
|
This returns <varname>description</varname> if it is not null, otherwise
|
|
<varname>short_description</varname> if it is not null, otherwise <literal>(none)</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
The arguments must all be convertible to a common data type, which
|
|
will be the type of the result (see
|
|
<xref linkend="typeconv-union-case"/> for details).
|
|
</para>
|
|
|
|
<para>
|
|
Like a <token>CASE</token> expression, <function>COALESCE</function> only
|
|
evaluates the arguments that are needed to determine the result;
|
|
that is, arguments to the right of the first non-null argument are
|
|
not evaluated. This SQL-standard function provides capabilities similar
|
|
to <function>NVL</function> and <function>IFNULL</function>, which are used in some other
|
|
database systems.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-nullif">
|
|
<title><literal>NULLIF</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>NULLIF</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>NULLIF</function>(<replaceable>value1</replaceable>, <replaceable>value2</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>NULLIF</function> function returns a null value if
|
|
<replaceable>value1</replaceable> equals <replaceable>value2</replaceable>;
|
|
otherwise it returns <replaceable>value1</replaceable>.
|
|
This can be used to perform the inverse operation of the
|
|
<function>COALESCE</function> example given above:
|
|
<programlisting>
|
|
SELECT NULLIF(value, '(none)') ...
|
|
</programlisting>
|
|
In this example, if <literal>value</literal> is <literal>(none)</literal>,
|
|
null is returned, otherwise the value of <literal>value</literal>
|
|
is returned.
|
|
</para>
|
|
|
|
<para>
|
|
The two arguments must be of comparable types.
|
|
To be specific, they are compared exactly as if you had
|
|
written <literal><replaceable>value1</replaceable>
|
|
= <replaceable>value2</replaceable></literal>, so there must be a
|
|
suitable <literal>=</literal> operator available.
|
|
</para>
|
|
|
|
<para>
|
|
The result has the same type as the first argument — but there is
|
|
a subtlety. What is actually returned is the first argument of the
|
|
implied <literal>=</literal> operator, and in some cases that will have
|
|
been promoted to match the second argument's type. For
|
|
example, <literal>NULLIF(1, 2.2)</literal> yields <type>numeric</type>,
|
|
because there is no <type>integer</type> <literal>=</literal>
|
|
<type>numeric</type> operator,
|
|
only <type>numeric</type> <literal>=</literal> <type>numeric</type>.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-greatest-least">
|
|
<title><literal>GREATEST</literal> and <literal>LEAST</literal></title>
|
|
|
|
<indexterm>
|
|
<primary>GREATEST</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>LEAST</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>GREATEST</function>(<replaceable>value</replaceable> <optional>, ...</optional>)
|
|
</synopsis>
|
|
<synopsis>
|
|
<function>LEAST</function>(<replaceable>value</replaceable> <optional>, ...</optional>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The <function>GREATEST</function> and <function>LEAST</function> functions select the
|
|
largest or smallest value from a list of any number of expressions.
|
|
The expressions must all be convertible to a common data type, which
|
|
will be the type of the result
|
|
(see <xref linkend="typeconv-union-case"/> for details).
|
|
</para>
|
|
|
|
<para>
|
|
NULL values in the argument list are ignored. The result will be NULL
|
|
only if all the expressions evaluate to NULL. (This is a deviation from
|
|
the SQL standard. According to the standard, the return value is NULL if
|
|
any argument is NULL. Some other databases behave this way.)
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-array">
|
|
<title>Array Functions and Operators</title>
|
|
|
|
<para>
|
|
<xref linkend="array-operators-table"/> shows the specialized operators
|
|
available for array types.
|
|
In addition to those, the usual comparison operators shown in <xref
|
|
linkend="functions-comparison-op-table"/> are available for
|
|
arrays. The comparison operators compare the array contents
|
|
element-by-element, using the default B-tree comparison function for
|
|
the element data type, and sort based on the first difference.
|
|
In multidimensional arrays the elements are visited in row-major order
|
|
(last subscript varies most rapidly).
|
|
If the contents of two arrays are equal but the dimensionality is
|
|
different, the first difference in the dimensionality information
|
|
determines the sort order.
|
|
</para>
|
|
|
|
<table id="array-operators-table">
|
|
<title>Array Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyarray</type> <literal>@></literal> <type>anyarray</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the first array contain the second, that is, does each element
|
|
appearing in the second array equal some element of the first array?
|
|
(Duplicates are not treated specially,
|
|
thus <literal>ARRAY[1]</literal> and <literal>ARRAY[1,1]</literal> are
|
|
each considered to contain the other.)
|
|
</para>
|
|
<para>
|
|
<literal>ARRAY[1,4,3] @> ARRAY[3,1,3]</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyarray</type> <literal><@</literal> <type>anyarray</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the first array contained by the second?
|
|
</para>
|
|
<para>
|
|
<literal>ARRAY[2,2,7] <@ ARRAY[1,7,4,2,6]</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyarray</type> <literal>&&</literal> <type>anyarray</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Do the arrays overlap, that is, have any elements in common?
|
|
</para>
|
|
<para>
|
|
<literal>ARRAY[1,4,3] && ARRAY[2,1]</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anycompatiblearray</type> <literal>||</literal> <type>anycompatiblearray</type>
|
|
<returnvalue>anycompatiblearray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates the two arrays. Concatenating a null or empty array is a
|
|
no-op; otherwise the arrays must have the same number of dimensions
|
|
(as illustrated by the first example) or differ in number of
|
|
dimensions by one (as illustrated by the second).
|
|
If the arrays are not of identical element types, they will be coerced
|
|
to a common type (see <xref linkend="typeconv-union-case"/>).
|
|
</para>
|
|
<para>
|
|
<literal>ARRAY[1,2,3] || ARRAY[4,5,6,7]</literal>
|
|
<returnvalue>{1,2,3,4,5,6,7}</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9.9]]</literal>
|
|
<returnvalue>{{1,2,3},{4,5,6},{7,8,9.9}}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anycompatible</type> <literal>||</literal> <type>anycompatiblearray</type>
|
|
<returnvalue>anycompatiblearray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates an element onto the front of an array (which must be
|
|
empty or one-dimensional).
|
|
</para>
|
|
<para>
|
|
<literal>3 || ARRAY[4,5,6]</literal>
|
|
<returnvalue>{3,4,5,6}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anycompatiblearray</type> <literal>||</literal> <type>anycompatible</type>
|
|
<returnvalue>anycompatiblearray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates an element onto the end of an array (which must be
|
|
empty or one-dimensional).
|
|
</para>
|
|
<para>
|
|
<literal>ARRAY[4,5,6] || 7</literal>
|
|
<returnvalue>{4,5,6,7}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
See <xref linkend="arrays"/> for more details about array operator
|
|
behavior. See <xref linkend="indexes-types"/> for more details about
|
|
which operators support indexed operations.
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="array-functions-table"/> shows the functions
|
|
available for use with array types. See <xref linkend="arrays"/>
|
|
for more information and examples of the use of these functions.
|
|
</para>
|
|
|
|
<table id="array-functions-table">
|
|
<title>Array Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_append</primary>
|
|
</indexterm>
|
|
<function>array_append</function> ( <type>anycompatiblearray</type>, <type>anycompatible</type> )
|
|
<returnvalue>anycompatiblearray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Appends an element to the end of an array (same as
|
|
the <type>anycompatiblearray</type> <literal>||</literal> <type>anycompatible</type>
|
|
operator).
|
|
</para>
|
|
<para>
|
|
<literal>array_append(ARRAY[1,2], 3)</literal>
|
|
<returnvalue>{1,2,3}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_cat</primary>
|
|
</indexterm>
|
|
<function>array_cat</function> ( <type>anycompatiblearray</type>, <type>anycompatiblearray</type> )
|
|
<returnvalue>anycompatiblearray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates two arrays (same as
|
|
the <type>anycompatiblearray</type> <literal>||</literal> <type>anycompatiblearray</type>
|
|
operator).
|
|
</para>
|
|
<para>
|
|
<literal>array_cat(ARRAY[1,2,3], ARRAY[4,5])</literal>
|
|
<returnvalue>{1,2,3,4,5}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_dims</primary>
|
|
</indexterm>
|
|
<function>array_dims</function> ( <type>anyarray</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a text representation of the array's dimensions.
|
|
</para>
|
|
<para>
|
|
<literal>array_dims(ARRAY[[1,2,3], [4,5,6]])</literal>
|
|
<returnvalue>[1:2][1:3]</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_fill</primary>
|
|
</indexterm>
|
|
<function>array_fill</function> ( <type>anyelement</type>, <type>integer[]</type>
|
|
<optional>, <type>integer[]</type> </optional> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an array filled with copies of the given value, having
|
|
dimensions of the lengths specified by the second argument.
|
|
The optional third argument supplies lower-bound values for each
|
|
dimension (which default to all <literal>1</literal>).
|
|
</para>
|
|
<para>
|
|
<literal>array_fill(11, ARRAY[2,3])</literal>
|
|
<returnvalue>{{11,11,11},{11,11,11}}</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>array_fill(7, ARRAY[3], ARRAY[2])</literal>
|
|
<returnvalue>[2:4]={7,7,7}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_length</primary>
|
|
</indexterm>
|
|
<function>array_length</function> ( <type>anyarray</type>, <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the length of the requested array dimension.
|
|
(Produces NULL instead of 0 for empty or missing array dimensions.)
|
|
</para>
|
|
<para>
|
|
<literal>array_length(array[1,2,3], 1)</literal>
|
|
<returnvalue>3</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>array_length(array[]::int[], 1)</literal>
|
|
<returnvalue>NULL</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>array_length(array['text'], 2)</literal>
|
|
<returnvalue>NULL</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_lower</primary>
|
|
</indexterm>
|
|
<function>array_lower</function> ( <type>anyarray</type>, <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the lower bound of the requested array dimension.
|
|
</para>
|
|
<para>
|
|
<literal>array_lower('[0:2]={1,2,3}'::integer[], 1)</literal>
|
|
<returnvalue>0</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_ndims</primary>
|
|
</indexterm>
|
|
<function>array_ndims</function> ( <type>anyarray</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of dimensions of the array.
|
|
</para>
|
|
<para>
|
|
<literal>array_ndims(ARRAY[[1,2,3], [4,5,6]])</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_position</primary>
|
|
</indexterm>
|
|
<function>array_position</function> ( <type>anycompatiblearray</type>, <type>anycompatible</type> <optional>, <type>integer</type> </optional> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the subscript of the first occurrence of the second argument
|
|
in the array, or <literal>NULL</literal> if it's not present.
|
|
If the third argument is given, the search begins at that subscript.
|
|
The array must be one-dimensional.
|
|
Comparisons are done using <literal>IS NOT DISTINCT FROM</literal>
|
|
semantics, so it is possible to search for <literal>NULL</literal>.
|
|
</para>
|
|
<para>
|
|
<literal>array_position(ARRAY['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'], 'mon')</literal>
|
|
<returnvalue>2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_positions</primary>
|
|
</indexterm>
|
|
<function>array_positions</function> ( <type>anycompatiblearray</type>, <type>anycompatible</type> )
|
|
<returnvalue>integer[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an array of the subscripts of all occurrences of the second
|
|
argument in the array given as first argument.
|
|
The array must be one-dimensional.
|
|
Comparisons are done using <literal>IS NOT DISTINCT FROM</literal>
|
|
semantics, so it is possible to search for <literal>NULL</literal>.
|
|
<literal>NULL</literal> is returned only if the array
|
|
is <literal>NULL</literal>; if the value is not found in the array, an
|
|
empty array is returned.
|
|
</para>
|
|
<para>
|
|
<literal>array_positions(ARRAY['A','A','B','A'], 'A')</literal>
|
|
<returnvalue>{1,2,4}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_prepend</primary>
|
|
</indexterm>
|
|
<function>array_prepend</function> ( <type>anycompatible</type>, <type>anycompatiblearray</type> )
|
|
<returnvalue>anycompatiblearray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Prepends an element to the beginning of an array (same as
|
|
the <type>anycompatible</type> <literal>||</literal> <type>anycompatiblearray</type>
|
|
operator).
|
|
</para>
|
|
<para>
|
|
<literal>array_prepend(1, ARRAY[2,3])</literal>
|
|
<returnvalue>{1,2,3}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_remove</primary>
|
|
</indexterm>
|
|
<function>array_remove</function> ( <type>anycompatiblearray</type>, <type>anycompatible</type> )
|
|
<returnvalue>anycompatiblearray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes all elements equal to the given value from the array.
|
|
The array must be one-dimensional.
|
|
Comparisons are done using <literal>IS NOT DISTINCT FROM</literal>
|
|
semantics, so it is possible to remove <literal>NULL</literal>s.
|
|
</para>
|
|
<para>
|
|
<literal>array_remove(ARRAY[1,2,3,2], 2)</literal>
|
|
<returnvalue>{1,3}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_replace</primary>
|
|
</indexterm>
|
|
<function>array_replace</function> ( <type>anycompatiblearray</type>, <type>anycompatible</type>, <type>anycompatible</type> )
|
|
<returnvalue>anycompatiblearray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Replaces each array element equal to the second argument with the
|
|
third argument.
|
|
</para>
|
|
<para>
|
|
<literal>array_replace(ARRAY[1,2,5,4], 5, 3)</literal>
|
|
<returnvalue>{1,2,3,4}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_sample</primary>
|
|
</indexterm>
|
|
<function>array_sample</function> ( <parameter>array</parameter> <type>anyarray</type>, <parameter>n</parameter> <type>integer</type> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an array of <parameter>n</parameter> items randomly selected
|
|
from <parameter>array</parameter>. <parameter>n</parameter> may not
|
|
exceed the length of <parameter>array</parameter>'s first dimension.
|
|
If <parameter>array</parameter> is multi-dimensional,
|
|
an <quote>item</quote> is a slice having a given first subscript.
|
|
</para>
|
|
<para>
|
|
<literal>array_sample(ARRAY[1,2,3,4,5,6], 3)</literal>
|
|
<returnvalue>{2,6,1}</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>array_sample(ARRAY[[1,2],[3,4],[5,6]], 2)</literal>
|
|
<returnvalue>{{5,6},{1,2}}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_shuffle</primary>
|
|
</indexterm>
|
|
<function>array_shuffle</function> ( <type>anyarray</type> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Randomly shuffles the first dimension of the array.
|
|
</para>
|
|
<para>
|
|
<literal>array_shuffle(ARRAY[[1,2],[3,4],[5,6]])</literal>
|
|
<returnvalue>{{5,6},{1,2},{3,4}}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm id="function-array-to-string">
|
|
<primary>array_to_string</primary>
|
|
</indexterm>
|
|
<function>array_to_string</function> ( <parameter>array</parameter> <type>anyarray</type>, <parameter>delimiter</parameter> <type>text</type> <optional>, <parameter>null_string</parameter> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts each array element to its text representation, and
|
|
concatenates those separated by
|
|
the <parameter>delimiter</parameter> string.
|
|
If <parameter>null_string</parameter> is given and is
|
|
not <literal>NULL</literal>, then <literal>NULL</literal> array
|
|
entries are represented by that string; otherwise, they are omitted.
|
|
See also <link linkend="function-string-to-array"><function>string_to_array</function></link>.
|
|
</para>
|
|
<para>
|
|
<literal>array_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*')</literal>
|
|
<returnvalue>1,2,3,*,5</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_upper</primary>
|
|
</indexterm>
|
|
<function>array_upper</function> ( <type>anyarray</type>, <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the upper bound of the requested array dimension.
|
|
</para>
|
|
<para>
|
|
<literal>array_upper(ARRAY[1,8,3,7], 1)</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cardinality</primary>
|
|
</indexterm>
|
|
<function>cardinality</function> ( <type>anyarray</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the total number of elements in the array, or 0 if the array
|
|
is empty.
|
|
</para>
|
|
<para>
|
|
<literal>cardinality(ARRAY[[1,2],[3,4]])</literal>
|
|
<returnvalue>4</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>trim_array</primary>
|
|
</indexterm>
|
|
<function>trim_array</function> ( <parameter>array</parameter> <type>anyarray</type>, <parameter>n</parameter> <type>integer</type> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Trims an array by removing the last <parameter>n</parameter> elements.
|
|
If the array is multidimensional, only the first dimension is trimmed.
|
|
</para>
|
|
<para>
|
|
<literal>trim_array(ARRAY[1,2,3,4,5,6], 2)</literal>
|
|
<returnvalue>{1,2,3,4}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>unnest</primary>
|
|
</indexterm>
|
|
<function>unnest</function> ( <type>anyarray</type> )
|
|
<returnvalue>setof anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Expands an array into a set of rows.
|
|
The array's elements are read out in storage order.
|
|
</para>
|
|
<para>
|
|
<literal>unnest(ARRAY[1,2])</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
1
|
|
2
|
|
</programlisting>
|
|
</para>
|
|
<para>
|
|
<literal>unnest(ARRAY[['foo','bar'],['baz','quux']])</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
foo
|
|
bar
|
|
baz
|
|
quux
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>unnest</function> ( <type>anyarray</type>, <type>anyarray</type> <optional>, ... </optional> )
|
|
<returnvalue>setof anyelement, anyelement [, ... ]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Expands multiple arrays (possibly of different data types) into a set of
|
|
rows. If the arrays are not all the same length then the shorter ones
|
|
are padded with <literal>NULL</literal>s. This form is only allowed
|
|
in a query's FROM clause; see <xref linkend="queries-tablefunctions"/>.
|
|
</para>
|
|
<para>
|
|
<literal>select * from unnest(ARRAY[1,2], ARRAY['foo','bar','baz']) as x(a,b)</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
a | b
|
|
---+-----
|
|
1 | foo
|
|
2 | bar
|
|
| baz
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
See also <xref linkend="functions-aggregate"/> about the aggregate
|
|
function <function>array_agg</function> for use with arrays.
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-range">
|
|
<title>Range/Multirange Functions and Operators</title>
|
|
|
|
<para>
|
|
See <xref linkend="rangetypes"/> for an overview of range types.
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="range-operators-table"/> shows the specialized operators
|
|
available for range types.
|
|
<xref linkend="multirange-operators-table"/> shows the specialized operators
|
|
available for multirange types.
|
|
In addition to those, the usual comparison operators shown in
|
|
<xref linkend="functions-comparison-op-table"/> are available for range
|
|
and multirange types. The comparison operators order first by the range lower
|
|
bounds, and only if those are equal do they compare the upper bounds. The
|
|
multirange operators compare each range until one is unequal. This
|
|
does not usually result in a useful overall ordering, but the operators are
|
|
provided to allow unique indexes to be constructed on ranges.
|
|
</para>
|
|
|
|
<table id="range-operators-table">
|
|
<title>Range Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>@></literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the first range contain the second?
|
|
</para>
|
|
<para>
|
|
<literal>int4range(2,4) @> int4range(2,3)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>@></literal> <type>anyelement</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the range contain the element?
|
|
</para>
|
|
<para>
|
|
<literal>'[2011-01-01,2011-03-01)'::tsrange @> '2011-01-10'::timestamp</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal><@</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the first range contained by the second?
|
|
</para>
|
|
<para>
|
|
<literal>int4range(2,4) <@ int4range(1,7)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyelement</type> <literal><@</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the element contained in the range?
|
|
</para>
|
|
<para>
|
|
<literal>42 <@ int4range(1,7)</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>&&</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Do the ranges overlap, that is, have any elements in common?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(3,7) && int8range(4,12)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal><<</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the first range strictly left of the second?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(1,10) << int8range(100,110)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>>></literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the first range strictly right of the second?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(50,60) >> int8range(20,30)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>&<</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the first range not extend to the right of the second?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(1,20) &< int8range(18,20)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>&></literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the first range not extend to the left of the second?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(7,20) &> int8range(5,10)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>-|-</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Are the ranges adjacent?
|
|
</para>
|
|
<para>
|
|
<literal>numrange(1.1,2.2) -|- numrange(2.2,3.3)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>+</literal> <type>anyrange</type>
|
|
<returnvalue>anyrange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the union of the ranges. The ranges must overlap or be
|
|
adjacent, so that the union is a single range (but
|
|
see <function>range_merge()</function>).
|
|
</para>
|
|
<para>
|
|
<literal>numrange(5,15) + numrange(10,20)</literal>
|
|
<returnvalue>[5,20)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>*</literal> <type>anyrange</type>
|
|
<returnvalue>anyrange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the intersection of the ranges.
|
|
</para>
|
|
<para>
|
|
<literal>int8range(5,15) * int8range(10,20)</literal>
|
|
<returnvalue>[10,15)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>-</literal> <type>anyrange</type>
|
|
<returnvalue>anyrange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the difference of the ranges. The second range must not be
|
|
contained in the first in such a way that the difference would not be
|
|
a single range.
|
|
</para>
|
|
<para>
|
|
<literal>int8range(5,15) - int8range(10,20)</literal>
|
|
<returnvalue>[5,10)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="multirange-operators-table">
|
|
<title>Multirange Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>@></literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the first multirange contain the second?
|
|
</para>
|
|
<para>
|
|
<literal>'{[2,4)}'::int4multirange @> '{[2,3)}'::int4multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>@></literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the multirange contain the range?
|
|
</para>
|
|
<para>
|
|
<literal>'{[2,4)}'::int4multirange @> int4range(2,3)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>@></literal> <type>anyelement</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the multirange contain the element?
|
|
</para>
|
|
<para>
|
|
<literal>'{[2011-01-01,2011-03-01)}'::tsmultirange @> '2011-01-10'::timestamp</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>@></literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the range contain the multirange?
|
|
</para>
|
|
<para>
|
|
<literal>'[2,4)'::int4range @> '{[2,3)}'::int4multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal><@</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the first multirange contained by the second?
|
|
</para>
|
|
<para>
|
|
<literal>'{[2,4)}'::int4multirange <@ '{[1,7)}'::int4multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal><@</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the multirange contained by the range?
|
|
</para>
|
|
<para>
|
|
<literal>'{[2,4)}'::int4multirange <@ int4range(1,7)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal><@</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the range contained by the multirange?
|
|
</para>
|
|
<para>
|
|
<literal>int4range(2,4) <@ '{[1,7)}'::int4multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyelement</type> <literal><@</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the element contained by the multirange?
|
|
</para>
|
|
<para>
|
|
<literal>4 <@ '{[1,7)}'::int4multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>&&</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Do the multiranges overlap, that is, have any elements in common?
|
|
</para>
|
|
<para>
|
|
<literal>'{[3,7)}'::int8multirange && '{[4,12)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>&&</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the multirange overlap the range?
|
|
</para>
|
|
<para>
|
|
<literal>'{[3,7)}'::int8multirange && int8range(4,12)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>&&</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the range overlap the multirange?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(3,7) && '{[4,12)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal><<</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the first multirange strictly left of the second?
|
|
</para>
|
|
<para>
|
|
<literal>'{[1,10)}'::int8multirange << '{[100,110)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal><<</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the multirange strictly left of the range?
|
|
</para>
|
|
<para>
|
|
<literal>'{[1,10)}'::int8multirange << int8range(100,110)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal><<</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the range strictly left of the multirange?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(1,10) << '{[100,110)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>>></literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the first multirange strictly right of the second?
|
|
</para>
|
|
<para>
|
|
<literal>'{[50,60)}'::int8multirange >> '{[20,30)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>>></literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the multirange strictly right of the range?
|
|
</para>
|
|
<para>
|
|
<literal>'{[50,60)}'::int8multirange >> int8range(20,30)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>>></literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the range strictly right of the multirange?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(50,60) >> '{[20,30)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>&<</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the first multirange not extend to the right of the second?
|
|
</para>
|
|
<para>
|
|
<literal>'{[1,20)}'::int8multirange &< '{[18,20)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>&<</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the multirange not extend to the right of the range?
|
|
</para>
|
|
<para>
|
|
<literal>'{[1,20)}'::int8multirange &< int8range(18,20)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>&<</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the range not extend to the right of the multirange?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(1,20) &< '{[18,20)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>&></literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the first multirange not extend to the left of the second?
|
|
</para>
|
|
<para>
|
|
<literal>'{[7,20)}'::int8multirange &> '{[5,10)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>&></literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the multirange not extend to the left of the range?
|
|
</para>
|
|
<para>
|
|
<literal>'{[7,20)}'::int8multirange &> int8range(5,10)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>&></literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the range not extend to the left of the multirange?
|
|
</para>
|
|
<para>
|
|
<literal>int8range(7,20) &> '{[5,10)}'::int8multirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>-|-</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Are the multiranges adjacent?
|
|
</para>
|
|
<para>
|
|
<literal>'{[1.1,2.2)}'::nummultirange -|- '{[2.2,3.3)}'::nummultirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>-|-</literal> <type>anyrange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the multirange adjacent to the range?
|
|
</para>
|
|
<para>
|
|
<literal>'{[1.1,2.2)}'::nummultirange -|- numrange(2.2,3.3)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anyrange</type> <literal>-|-</literal> <type>anymultirange</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the range adjacent to the multirange?
|
|
</para>
|
|
<para>
|
|
<literal>numrange(1.1,2.2) -|- '{[2.2,3.3)}'::nummultirange</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>+</literal> <type>anymultirange</type>
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the union of the multiranges. The multiranges need not overlap
|
|
or be adjacent.
|
|
</para>
|
|
<para>
|
|
<literal>'{[5,10)}'::nummultirange + '{[15,20)}'::nummultirange</literal>
|
|
<returnvalue>{[5,10), [15,20)}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>*</literal> <type>anymultirange</type>
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the intersection of the multiranges.
|
|
</para>
|
|
<para>
|
|
<literal>'{[5,15)}'::int8multirange * '{[10,20)}'::int8multirange</literal>
|
|
<returnvalue>{[10,15)}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>anymultirange</type> <literal>-</literal> <type>anymultirange</type>
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the difference of the multiranges.
|
|
</para>
|
|
<para>
|
|
<literal>'{[5,20)}'::int8multirange - '{[10,15)}'::int8multirange</literal>
|
|
<returnvalue>{[5,10), [15,20)}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The left-of/right-of/adjacent operators always return false when an empty
|
|
range or multirange is involved; that is, an empty range is not considered to
|
|
be either before or after any other range.
|
|
</para>
|
|
|
|
<para>
|
|
Elsewhere empty ranges and multiranges are treated as the additive identity:
|
|
anything unioned with an empty value is itself. Anything minus an empty
|
|
value is itself. An empty multirange has exactly the same points as an empty
|
|
range. Every range contains the empty range. Every multirange contains as many
|
|
empty ranges as you like.
|
|
</para>
|
|
|
|
<para>
|
|
The range union and difference operators will fail if the resulting range would
|
|
need to contain two disjoint sub-ranges, as such a range cannot be
|
|
represented. There are separate operators for union and difference that take
|
|
multirange parameters and return a multirange, and they do not fail even if
|
|
their arguments are disjoint. So if you need a union or difference operation
|
|
for ranges that may be disjoint, you can avoid errors by first casting your
|
|
ranges to multiranges.
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="range-functions-table"/> shows the functions
|
|
available for use with range types.
|
|
<xref linkend="multirange-functions-table"/> shows the functions
|
|
available for use with multirange types.
|
|
</para>
|
|
|
|
<table id="range-functions-table">
|
|
<title>Range Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lower</primary>
|
|
</indexterm>
|
|
<function>lower</function> ( <type>anyrange</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the lower bound of the range (<literal>NULL</literal> if the
|
|
range is empty or has no lower bound).
|
|
</para>
|
|
<para>
|
|
<literal>lower(numrange(1.1,2.2))</literal>
|
|
<returnvalue>1.1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>upper</primary>
|
|
</indexterm>
|
|
<function>upper</function> ( <type>anyrange</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the upper bound of the range (<literal>NULL</literal> if the
|
|
range is empty or has no upper bound).
|
|
</para>
|
|
<para>
|
|
<literal>upper(numrange(1.1,2.2))</literal>
|
|
<returnvalue>2.2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>isempty</primary>
|
|
</indexterm>
|
|
<function>isempty</function> ( <type>anyrange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the range empty?
|
|
</para>
|
|
<para>
|
|
<literal>isempty(numrange(1.1,2.2))</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lower_inc</primary>
|
|
</indexterm>
|
|
<function>lower_inc</function> ( <type>anyrange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the range's lower bound inclusive?
|
|
</para>
|
|
<para>
|
|
<literal>lower_inc(numrange(1.1,2.2))</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>upper_inc</primary>
|
|
</indexterm>
|
|
<function>upper_inc</function> ( <type>anyrange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the range's upper bound inclusive?
|
|
</para>
|
|
<para>
|
|
<literal>upper_inc(numrange(1.1,2.2))</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lower_inf</primary>
|
|
</indexterm>
|
|
<function>lower_inf</function> ( <type>anyrange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the range have no lower bound? (A lower bound of
|
|
<literal>-Infinity</literal> returns false.)
|
|
</para>
|
|
<para>
|
|
<literal>lower_inf('(,)'::daterange)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>upper_inf</primary>
|
|
</indexterm>
|
|
<function>upper_inf</function> ( <type>anyrange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the range have no upper bound? (An upper bound of
|
|
<literal>Infinity</literal> returns false.)
|
|
</para>
|
|
<para>
|
|
<literal>upper_inf('(,)'::daterange)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>range_merge</primary>
|
|
</indexterm>
|
|
<function>range_merge</function> ( <type>anyrange</type>, <type>anyrange</type> )
|
|
<returnvalue>anyrange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the smallest range that includes both of the given ranges.
|
|
</para>
|
|
<para>
|
|
<literal>range_merge('[1,2)'::int4range, '[3,4)'::int4range)</literal>
|
|
<returnvalue>[1,4)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="multirange-functions-table">
|
|
<title>Multirange Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lower</primary>
|
|
</indexterm>
|
|
<function>lower</function> ( <type>anymultirange</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the lower bound of the multirange (<literal>NULL</literal> if the
|
|
multirange is empty has no lower bound).
|
|
</para>
|
|
<para>
|
|
<literal>lower('{[1.1,2.2)}'::nummultirange)</literal>
|
|
<returnvalue>1.1</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>upper</primary>
|
|
</indexterm>
|
|
<function>upper</function> ( <type>anymultirange</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Extracts the upper bound of the multirange (<literal>NULL</literal> if the
|
|
multirange is empty or has no upper bound).
|
|
</para>
|
|
<para>
|
|
<literal>upper('{[1.1,2.2)}'::nummultirange)</literal>
|
|
<returnvalue>2.2</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>isempty</primary>
|
|
</indexterm>
|
|
<function>isempty</function> ( <type>anymultirange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the multirange empty?
|
|
</para>
|
|
<para>
|
|
<literal>isempty('{[1.1,2.2)}'::nummultirange)</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lower_inc</primary>
|
|
</indexterm>
|
|
<function>lower_inc</function> ( <type>anymultirange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the multirange's lower bound inclusive?
|
|
</para>
|
|
<para>
|
|
<literal>lower_inc('{[1.1,2.2)}'::nummultirange)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>upper_inc</primary>
|
|
</indexterm>
|
|
<function>upper_inc</function> ( <type>anymultirange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the multirange's upper bound inclusive?
|
|
</para>
|
|
<para>
|
|
<literal>upper_inc('{[1.1,2.2)}'::nummultirange)</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lower_inf</primary>
|
|
</indexterm>
|
|
<function>lower_inf</function> ( <type>anymultirange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the multirange have no lower bound? (A lower bound of
|
|
<literal>-Infinity</literal> returns false.)
|
|
</para>
|
|
<para>
|
|
<literal>lower_inf('{(,)}'::datemultirange)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>upper_inf</primary>
|
|
</indexterm>
|
|
<function>upper_inf</function> ( <type>anymultirange</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does the multirange have no upper bound? (An upper bound of
|
|
<literal>Infinity</literal> returns false.)
|
|
</para>
|
|
<para>
|
|
<literal>upper_inf('{(,)}'::datemultirange)</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>range_merge</primary>
|
|
</indexterm>
|
|
<function>range_merge</function> ( <type>anymultirange</type> )
|
|
<returnvalue>anyrange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the smallest range that includes the entire multirange.
|
|
</para>
|
|
<para>
|
|
<literal>range_merge('{[1,2), [3,4)}'::int4multirange)</literal>
|
|
<returnvalue>[1,4)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>multirange (function)</primary>
|
|
</indexterm>
|
|
<function>multirange</function> ( <type>anyrange</type> )
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a multirange containing just the given range.
|
|
</para>
|
|
<para>
|
|
<literal>multirange('[1,2)'::int4range)</literal>
|
|
<returnvalue>{[1,2)}</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>unnest</primary>
|
|
<secondary>for multirange</secondary>
|
|
</indexterm>
|
|
<function>unnest</function> ( <type>anymultirange</type> )
|
|
<returnvalue>setof anyrange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Expands a multirange into a set of ranges in ascending order.
|
|
</para>
|
|
<para>
|
|
<literal>unnest('{[1,2), [3,4)}'::int4multirange)</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
[1,2)
|
|
[3,4)
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The <function>lower_inc</function>, <function>upper_inc</function>,
|
|
<function>lower_inf</function>, and <function>upper_inf</function>
|
|
functions all return false for an empty range or multirange.
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-aggregate">
|
|
<title>Aggregate Functions</title>
|
|
|
|
<indexterm zone="functions-aggregate">
|
|
<primary>aggregate function</primary>
|
|
<secondary>built-in</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<firstterm>Aggregate functions</firstterm> compute a single result
|
|
from a set of input values. The built-in general-purpose aggregate
|
|
functions are listed in <xref linkend="functions-aggregate-table"/>
|
|
while statistical aggregates are in <xref
|
|
linkend="functions-aggregate-statistics-table"/>.
|
|
The built-in within-group ordered-set aggregate functions
|
|
are listed in <xref linkend="functions-orderedset-table"/>
|
|
while the built-in within-group hypothetical-set ones are in <xref
|
|
linkend="functions-hypothetical-table"/>. Grouping operations,
|
|
which are closely related to aggregate functions, are listed in
|
|
<xref linkend="functions-grouping-table"/>.
|
|
The special syntax considerations for aggregate
|
|
functions are explained in <xref linkend="syntax-aggregates"/>.
|
|
Consult <xref linkend="tutorial-agg"/> for additional introductory
|
|
information.
|
|
</para>
|
|
|
|
<para>
|
|
Aggregate functions that support <firstterm>Partial Mode</firstterm>
|
|
are eligible to participate in various optimizations, such as parallel
|
|
aggregation.
|
|
</para>
|
|
|
|
<para>
|
|
While all aggregates below accept an optional
|
|
<literal>ORDER BY</literal> clause (as outlined in <xref
|
|
linkend="syntax-aggregates"/>), the clause has only been added to
|
|
aggregates whose output is affected by ordering.
|
|
</para>
|
|
|
|
<table id="functions-aggregate-table">
|
|
<title>General-Purpose Aggregate Functions</title>
|
|
<tgroup cols="2">
|
|
<colspec colname="col1" colwidth="10*"/>
|
|
<colspec colname="col2" colwidth="1*"/>
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
<entry>Partial Mode</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>any_value</primary>
|
|
</indexterm>
|
|
<function>any_value</function> ( <type>anyelement</type> )
|
|
<returnvalue><replaceable>same as input type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an arbitrary value from the non-null input values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>array_agg</primary>
|
|
</indexterm>
|
|
<function>array_agg</function> ( <type>anynonarray</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Collects all the input values, including nulls, into an array.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>array_agg</function> ( <type>anyarray</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates all the input arrays into an array of one higher
|
|
dimension. (The inputs must all have the same dimensionality, and
|
|
cannot be empty or null.)
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>average</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>avg</primary>
|
|
</indexterm>
|
|
<function>avg</function> ( <type>smallint</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>avg</function> ( <type>integer</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>avg</function> ( <type>bigint</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>avg</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>avg</function> ( <type>real</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>avg</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>avg</function> ( <type>interval</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the average (arithmetic mean) of all the non-null input
|
|
values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bit_and</primary>
|
|
</indexterm>
|
|
<function>bit_and</function> ( <type>smallint</type> )
|
|
<returnvalue>smallint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>bit_and</function> ( <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>bit_and</function> ( <type>bigint</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>bit_and</function> ( <type>bit</type> )
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the bitwise AND of all non-null input values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bit_or</primary>
|
|
</indexterm>
|
|
<function>bit_or</function> ( <type>smallint</type> )
|
|
<returnvalue>smallint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>bit_or</function> ( <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>bit_or</function> ( <type>bigint</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>bit_or</function> ( <type>bit</type> )
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the bitwise OR of all non-null input values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bit_xor</primary>
|
|
</indexterm>
|
|
<function>bit_xor</function> ( <type>smallint</type> )
|
|
<returnvalue>smallint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>bit_xor</function> ( <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>bit_xor</function> ( <type>bigint</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>bit_xor</function> ( <type>bit</type> )
|
|
<returnvalue>bit</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the bitwise exclusive OR of all non-null input values.
|
|
Can be useful as a checksum for an unordered set of values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bool_and</primary>
|
|
</indexterm>
|
|
<function>bool_and</function> ( <type>boolean</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns true if all non-null input values are true, otherwise false.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>bool_or</primary>
|
|
</indexterm>
|
|
<function>bool_or</function> ( <type>boolean</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns true if any non-null input value is true, otherwise false.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>count</primary>
|
|
</indexterm>
|
|
<function>count</function> ( <literal>*</literal> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the number of input rows.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>count</function> ( <type>"any"</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the number of input rows in which the input value is not
|
|
null.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>every</primary>
|
|
</indexterm>
|
|
<function>every</function> ( <type>boolean</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
This is the SQL standard's equivalent to <function>bool_and</function>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_agg</primary>
|
|
</indexterm>
|
|
<function>json_agg</function> ( <type>anyelement</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_agg</primary>
|
|
</indexterm>
|
|
<function>jsonb_agg</function> ( <type>anyelement</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Collects all the input values, including nulls, into a JSON array.
|
|
Values are converted to JSON as per <function>to_json</function>
|
|
or <function>to_jsonb</function>.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm><primary>json_objectagg</primary></indexterm>
|
|
<function>json_objectagg</function> (
|
|
<optional> { <replaceable>key_expression</replaceable> { <literal>VALUE</literal> | ':' } <replaceable>value_expression</replaceable> } </optional>
|
|
<optional> { <literal>NULL</literal> | <literal>ABSENT</literal> } <literal>ON NULL</literal> </optional>
|
|
<optional> { <literal>WITH</literal> | <literal>WITHOUT</literal> } <literal>UNIQUE</literal> <optional> <literal>KEYS</literal> </optional> </optional>
|
|
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
|
|
</para>
|
|
<para>
|
|
Behaves like <function>json_object</function><!-- xref -->, but as an
|
|
aggregate function, so it only takes one
|
|
<replaceable>key_expression</replaceable> and one
|
|
<replaceable>value_expression</replaceable> parameter.
|
|
</para>
|
|
<para>
|
|
<literal>SELECT json_objectagg(k:v) FROM (VALUES ('a'::text,current_date),('b',current_date + 1)) AS t(k,v)</literal>
|
|
<returnvalue>{ "a" : "2022-05-10", "b" : "2022-05-11" }</returnvalue>
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_object_agg</primary>
|
|
</indexterm>
|
|
<function>json_object_agg</function> ( <parameter>key</parameter>
|
|
<type>"any"</type>, <parameter>value</parameter>
|
|
<type>"any"</type>
|
|
<literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_object_agg</primary>
|
|
</indexterm>
|
|
<function>jsonb_object_agg</function> ( <parameter>key</parameter>
|
|
<type>"any"</type>, <parameter>value</parameter>
|
|
<type>"any"</type>
|
|
<literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Collects all the key/value pairs into a JSON object. Key arguments
|
|
are coerced to text; value arguments are converted as per
|
|
<function>to_json</function> or <function>to_jsonb</function>.
|
|
Values can be null, but keys cannot.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_object_agg_strict</primary>
|
|
</indexterm>
|
|
<function>json_object_agg_strict</function> (
|
|
<parameter>key</parameter> <type>"any"</type>,
|
|
<parameter>value</parameter> <type>"any"</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_object_agg_strict</primary>
|
|
</indexterm>
|
|
<function>jsonb_object_agg_strict</function> (
|
|
<parameter>key</parameter> <type>"any"</type>,
|
|
<parameter>value</parameter> <type>"any"</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Collects all the key/value pairs into a JSON object. Key arguments
|
|
are coerced to text; value arguments are converted as per
|
|
<function>to_json</function> or <function>to_jsonb</function>.
|
|
The <parameter>key</parameter> can not be null. If the
|
|
<parameter>value</parameter> is null then the entry is skipped,
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_object_agg_unique</primary>
|
|
</indexterm>
|
|
<function>json_object_agg_unique</function> (
|
|
<parameter>key</parameter> <type>"any"</type>,
|
|
<parameter>value</parameter> <type>"any"</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_object_agg_unique</primary>
|
|
</indexterm>
|
|
<function>jsonb_object_agg_unique</function> (
|
|
<parameter>key</parameter> <type>"any"</type>,
|
|
<parameter>value</parameter> <type>"any"</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Collects all the key/value pairs into a JSON object. Key arguments
|
|
are coerced to text; value arguments are converted as per
|
|
<function>to_json</function> or <function>to_jsonb</function>.
|
|
Values can be null, but keys cannot.
|
|
If there is a duplicate key an error is thrown.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm><primary>json_arrayagg</primary></indexterm>
|
|
<function>json_arrayagg</function> (
|
|
<optional> <replaceable>value_expression</replaceable> </optional>
|
|
<optional> <literal>ORDER BY</literal> <replaceable>sort_expression</replaceable> </optional>
|
|
<optional> { <literal>NULL</literal> | <literal>ABSENT</literal> } <literal>ON NULL</literal> </optional>
|
|
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
|
|
</para>
|
|
<para>
|
|
Behaves in the same way as <function>json_array</function>
|
|
but as an aggregate function so it only takes one
|
|
<replaceable>value_expression</replaceable> parameter.
|
|
If <literal>ABSENT ON NULL</literal> is specified, any NULL
|
|
values are omitted.
|
|
If <literal>ORDER BY</literal> is specified, the elements will
|
|
appear in the array in that order rather than in the input order.
|
|
</para>
|
|
<para>
|
|
<literal>SELECT json_arrayagg(v) FROM (VALUES(2),(1)) t(v)</literal>
|
|
<returnvalue>[2, 1]</returnvalue>
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_object_agg_unique_strict</primary>
|
|
</indexterm>
|
|
<function>json_object_agg_unique_strict</function> (
|
|
<parameter>key</parameter> <type>"any"</type>,
|
|
<parameter>value</parameter> <type>"any"</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_object_agg_unique_strict</primary>
|
|
</indexterm>
|
|
<function>jsonb_object_agg_unique_strict</function> (
|
|
<parameter>key</parameter> <type>"any"</type>,
|
|
<parameter>value</parameter> <type>"any"</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Collects all the key/value pairs into a JSON object. Key arguments
|
|
are coerced to text; value arguments are converted as per
|
|
<function>to_json</function> or <function>to_jsonb</function>.
|
|
The <parameter>key</parameter> can not be null. If the
|
|
<parameter>value</parameter> is null then the entry is skipped.
|
|
If there is a duplicate key an error is thrown.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>max</primary>
|
|
</indexterm>
|
|
<function>max</function> ( <replaceable>see text</replaceable> )
|
|
<returnvalue><replaceable>same as input type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the maximum of the non-null input
|
|
values. Available for any numeric, string, date/time, or enum type,
|
|
as well as <type>inet</type>, <type>interval</type>,
|
|
<type>money</type>, <type>oid</type>, <type>pg_lsn</type>,
|
|
<type>tid</type>, <type>xid8</type>,
|
|
and arrays of any of these types.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>min</primary>
|
|
</indexterm>
|
|
<function>min</function> ( <replaceable>see text</replaceable> )
|
|
<returnvalue><replaceable>same as input type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the minimum of the non-null input
|
|
values. Available for any numeric, string, date/time, or enum type,
|
|
as well as <type>inet</type>, <type>interval</type>,
|
|
<type>money</type>, <type>oid</type>, <type>pg_lsn</type>,
|
|
<type>tid</type>, <type>xid8</type>,
|
|
and arrays of any of these types.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>range_agg</primary>
|
|
</indexterm>
|
|
<function>range_agg</function> ( <parameter>value</parameter>
|
|
<type>anyrange</type> )
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>range_agg</function> ( <parameter>value</parameter>
|
|
<type>anymultirange</type> )
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the union of the non-null input values.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>range_intersect_agg</primary>
|
|
</indexterm>
|
|
<function>range_intersect_agg</function> ( <parameter>value</parameter>
|
|
<type>anyrange</type> )
|
|
<returnvalue>anyrange</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>range_intersect_agg</function> ( <parameter>value</parameter>
|
|
<type>anymultirange</type> )
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the intersection of the non-null input values.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_agg_strict</primary>
|
|
</indexterm>
|
|
<function>json_agg_strict</function> ( <type>anyelement</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_agg_strict</primary>
|
|
</indexterm>
|
|
<function>jsonb_agg_strict</function> ( <type>anyelement</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Collects all the input values, skipping nulls, into a JSON array.
|
|
Values are converted to JSON as per <function>to_json</function>
|
|
or <function>to_jsonb</function>.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>string_agg</primary>
|
|
</indexterm>
|
|
<function>string_agg</function> ( <parameter>value</parameter>
|
|
<type>text</type>, <parameter>delimiter</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>string_agg</function> ( <parameter>value</parameter>
|
|
<type>bytea</type>, <parameter>delimiter</parameter> <type>bytea</type>
|
|
<literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates the non-null input values into a string. Each value
|
|
after the first is preceded by the
|
|
corresponding <parameter>delimiter</parameter> (if it's not null).
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sum</primary>
|
|
</indexterm>
|
|
<function>sum</function> ( <type>smallint</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>integer</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>bigint</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>real</type> )
|
|
<returnvalue>real</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>interval</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>money</type> )
|
|
<returnvalue>money</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the sum of the non-null input values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>xmlagg</primary>
|
|
</indexterm>
|
|
<function>xmlagg</function> ( <type>xml</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>xml</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates the non-null XML input values (see
|
|
<xref linkend="functions-xml-xmlagg"/>).
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
It should be noted that except for <function>count</function>,
|
|
these functions return a null value when no rows are selected. In
|
|
particular, <function>sum</function> of no rows returns null, not
|
|
zero as one might expect, and <function>array_agg</function>
|
|
returns null rather than an empty array when there are no input
|
|
rows. The <function>coalesce</function> function can be used to
|
|
substitute zero or an empty array for null when necessary.
|
|
</para>
|
|
|
|
<para>
|
|
The aggregate functions <function>array_agg</function>,
|
|
<function>json_agg</function>, <function>jsonb_agg</function>,
|
|
<function>json_agg_strict</function>, <function>jsonb_agg_strict</function>,
|
|
<function>json_object_agg</function>, <function>jsonb_object_agg</function>,
|
|
<function>json_object_agg_strict</function>, <function>jsonb_object_agg_strict</function>,
|
|
<function>json_object_agg_unique</function>, <function>jsonb_object_agg_unique</function>,
|
|
<function>json_object_agg_unique_strict</function>,
|
|
<function>jsonb_object_agg_unique_strict</function>,
|
|
<function>string_agg</function>,
|
|
and <function>xmlagg</function>, as well as similar user-defined
|
|
aggregate functions, produce meaningfully different result values
|
|
depending on the order of the input values. This ordering is
|
|
unspecified by default, but can be controlled by writing an
|
|
<literal>ORDER BY</literal> clause within the aggregate call, as shown in
|
|
<xref linkend="syntax-aggregates"/>.
|
|
Alternatively, supplying the input values from a sorted subquery
|
|
will usually work. For example:
|
|
|
|
<screen><![CDATA[
|
|
SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
|
|
]]></screen>
|
|
|
|
Beware that this approach can fail if the outer query level contains
|
|
additional processing, such as a join, because that might cause the
|
|
subquery's output to be reordered before the aggregate is computed.
|
|
</para>
|
|
|
|
<note>
|
|
<indexterm>
|
|
<primary>ANY</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>SOME</primary>
|
|
</indexterm>
|
|
<para>
|
|
The boolean aggregates <function>bool_and</function> and
|
|
<function>bool_or</function> correspond to the standard SQL aggregates
|
|
<function>every</function> and <function>any</function> or
|
|
<function>some</function>.
|
|
<productname>PostgreSQL</productname>
|
|
supports <function>every</function>, but not <function>any</function>
|
|
or <function>some</function>, because there is an ambiguity built into
|
|
the standard syntax:
|
|
<programlisting>
|
|
SELECT b1 = ANY((SELECT b2 FROM t2 ...)) FROM t1 ...;
|
|
</programlisting>
|
|
Here <function>ANY</function> can be considered either as introducing
|
|
a subquery, or as being an aggregate function, if the subquery
|
|
returns one row with a Boolean value.
|
|
Thus the standard name cannot be given to these aggregates.
|
|
</para>
|
|
</note>
|
|
|
|
<note>
|
|
<para>
|
|
Users accustomed to working with other SQL database management
|
|
systems might be disappointed by the performance of the
|
|
<function>count</function> aggregate when it is applied to the
|
|
entire table. A query like:
|
|
<programlisting>
|
|
SELECT count(*) FROM sometable;
|
|
</programlisting>
|
|
will require effort proportional to the size of the table:
|
|
<productname>PostgreSQL</productname> will need to scan either the
|
|
entire table or the entirety of an index that includes all rows in
|
|
the table.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
<xref linkend="functions-aggregate-statistics-table"/> shows
|
|
aggregate functions typically used in statistical analysis.
|
|
(These are separated out merely to avoid cluttering the listing
|
|
of more-commonly-used aggregates.) Functions shown as
|
|
accepting <replaceable>numeric_type</replaceable> are available for all
|
|
the types <type>smallint</type>, <type>integer</type>,
|
|
<type>bigint</type>, <type>numeric</type>, <type>real</type>,
|
|
and <type>double precision</type>.
|
|
Where the description mentions
|
|
<parameter>N</parameter>, it means the
|
|
number of input rows for which all the input expressions are non-null.
|
|
In all cases, null is returned if the computation is meaningless,
|
|
for example when <parameter>N</parameter> is zero.
|
|
</para>
|
|
|
|
<indexterm>
|
|
<primary>statistics</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>linear regression</primary>
|
|
</indexterm>
|
|
|
|
<table id="functions-aggregate-statistics-table">
|
|
<title>Aggregate Functions for Statistics</title>
|
|
<tgroup cols="2">
|
|
<colspec colname="col1" colwidth="10*"/>
|
|
<colspec colname="col2" colwidth="1*"/>
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
<entry>Partial Mode</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>correlation</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>corr</primary>
|
|
</indexterm>
|
|
<function>corr</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the correlation coefficient.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>covariance</primary>
|
|
<secondary>population</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>covar_pop</primary>
|
|
</indexterm>
|
|
<function>covar_pop</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the population covariance.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>covariance</primary>
|
|
<secondary>sample</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>covar_samp</primary>
|
|
</indexterm>
|
|
<function>covar_samp</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the sample covariance.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_avgx</primary>
|
|
</indexterm>
|
|
<function>regr_avgx</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the average of the independent variable,
|
|
<literal>sum(<parameter>X</parameter>)/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_avgy</primary>
|
|
</indexterm>
|
|
<function>regr_avgy</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the average of the dependent variable,
|
|
<literal>sum(<parameter>Y</parameter>)/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_count</primary>
|
|
</indexterm>
|
|
<function>regr_count</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the number of rows in which both inputs are non-null.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regression intercept</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regr_intercept</primary>
|
|
</indexterm>
|
|
<function>regr_intercept</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the y-intercept of the least-squares-fit linear equation
|
|
determined by the
|
|
(<parameter>X</parameter>, <parameter>Y</parameter>) pairs.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_r2</primary>
|
|
</indexterm>
|
|
<function>regr_r2</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the square of the correlation coefficient.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regression slope</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regr_slope</primary>
|
|
</indexterm>
|
|
<function>regr_slope</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the slope of the least-squares-fit linear equation determined
|
|
by the (<parameter>X</parameter>, <parameter>Y</parameter>)
|
|
pairs.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_sxx</primary>
|
|
</indexterm>
|
|
<function>regr_sxx</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <quote>sum of squares</quote> of the independent
|
|
variable,
|
|
<literal>sum(<parameter>X</parameter>^2) - sum(<parameter>X</parameter>)^2/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_sxy</primary>
|
|
</indexterm>
|
|
<function>regr_sxy</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <quote>sum of products</quote> of independent times
|
|
dependent variables,
|
|
<literal>sum(<parameter>X</parameter>*<parameter>Y</parameter>) - sum(<parameter>X</parameter>) * sum(<parameter>Y</parameter>)/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_syy</primary>
|
|
</indexterm>
|
|
<function>regr_syy</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <quote>sum of squares</quote> of the dependent
|
|
variable,
|
|
<literal>sum(<parameter>Y</parameter>^2) - sum(<parameter>Y</parameter>)^2/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>standard deviation</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>stddev</primary>
|
|
</indexterm>
|
|
<function>stddev</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
This is a historical alias for <function>stddev_samp</function>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>standard deviation</primary>
|
|
<secondary>population</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>stddev_pop</primary>
|
|
</indexterm>
|
|
<function>stddev_pop</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
Computes the population standard deviation of the input values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>standard deviation</primary>
|
|
<secondary>sample</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>stddev_samp</primary>
|
|
</indexterm>
|
|
<function>stddev_samp</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
Computes the sample standard deviation of the input values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>variance</primary>
|
|
</indexterm>
|
|
<function>variance</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
This is a historical alias for <function>var_samp</function>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>variance</primary>
|
|
<secondary>population</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>var_pop</primary>
|
|
</indexterm>
|
|
<function>var_pop</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
Computes the population variance of the input values (square of the
|
|
population standard deviation).
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>variance</primary>
|
|
<secondary>sample</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>var_samp</primary>
|
|
</indexterm>
|
|
<function>var_samp</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
Computes the sample variance of the input values (square of the sample
|
|
standard deviation).
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-orderedset-table"/> shows some
|
|
aggregate functions that use the <firstterm>ordered-set aggregate</firstterm>
|
|
syntax. These functions are sometimes referred to as <quote>inverse
|
|
distribution</quote> functions. Their aggregated input is introduced by
|
|
<literal>ORDER BY</literal>, and they may also take a <firstterm>direct
|
|
argument</firstterm> that is not aggregated, but is computed only once.
|
|
All these functions ignore null values in their aggregated input.
|
|
For those that take a <parameter>fraction</parameter> parameter, the
|
|
fraction value must be between 0 and 1; an error is thrown if not.
|
|
However, a null <parameter>fraction</parameter> value simply produces a
|
|
null result.
|
|
</para>
|
|
|
|
<indexterm>
|
|
<primary>ordered-set aggregate</primary>
|
|
<secondary>built-in</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>inverse distribution</primary>
|
|
</indexterm>
|
|
|
|
<table id="functions-orderedset-table">
|
|
<title>Ordered-Set Aggregate Functions</title>
|
|
<tgroup cols="2">
|
|
<colspec colname="col1" colwidth="10*"/>
|
|
<colspec colname="col2" colwidth="1*"/>
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
<entry>Partial Mode</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>mode</primary>
|
|
<secondary>statistical</secondary>
|
|
</indexterm>
|
|
<function>mode</function> () <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>anyelement</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <firstterm>mode</firstterm>, the most frequent
|
|
value of the aggregated argument (arbitrarily choosing the first one
|
|
if there are multiple equally-frequent values). The aggregated
|
|
argument must be of a sortable type.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>percentile</primary>
|
|
<secondary>continuous</secondary>
|
|
</indexterm>
|
|
<function>percentile_cont</function> ( <parameter>fraction</parameter> <type>double precision</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>percentile_cont</function> ( <parameter>fraction</parameter> <type>double precision</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>interval</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <firstterm>continuous percentile</firstterm>, a value
|
|
corresponding to the specified <parameter>fraction</parameter>
|
|
within the ordered set of aggregated argument values. This will
|
|
interpolate between adjacent input items if needed.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>percentile_cont</function> ( <parameter>fractions</parameter> <type>double precision[]</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>double precision</type> )
|
|
<returnvalue>double precision[]</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>percentile_cont</function> ( <parameter>fractions</parameter> <type>double precision[]</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>interval</type> )
|
|
<returnvalue>interval[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes multiple continuous percentiles. The result is an array of
|
|
the same dimensions as the <parameter>fractions</parameter>
|
|
parameter, with each non-null element replaced by the (possibly
|
|
interpolated) value corresponding to that percentile.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>percentile</primary>
|
|
<secondary>discrete</secondary>
|
|
</indexterm>
|
|
<function>percentile_disc</function> ( <parameter>fraction</parameter> <type>double precision</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>anyelement</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <firstterm>discrete percentile</firstterm>, the first
|
|
value within the ordered set of aggregated argument values whose
|
|
position in the ordering equals or exceeds the
|
|
specified <parameter>fraction</parameter>. The aggregated
|
|
argument must be of a sortable type.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>percentile_disc</function> ( <parameter>fractions</parameter> <type>double precision[]</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>anyelement</type> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes multiple discrete percentiles. The result is an array of the
|
|
same dimensions as the <parameter>fractions</parameter> parameter,
|
|
with each non-null element replaced by the input value corresponding
|
|
to that percentile.
|
|
The aggregated argument must be of a sortable type.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<indexterm>
|
|
<primary>hypothetical-set aggregate</primary>
|
|
<secondary>built-in</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Each of the <quote>hypothetical-set</quote> aggregates listed in
|
|
<xref linkend="functions-hypothetical-table"/> is associated with a
|
|
window function of the same name defined in
|
|
<xref linkend="functions-window"/>. In each case, the aggregate's result
|
|
is the value that the associated window function would have
|
|
returned for the <quote>hypothetical</quote> row constructed from
|
|
<replaceable>args</replaceable>, if such a row had been added to the sorted
|
|
group of rows represented by the <replaceable>sorted_args</replaceable>.
|
|
For each of these functions, the list of direct arguments
|
|
given in <replaceable>args</replaceable> must match the number and types of
|
|
the aggregated arguments given in <replaceable>sorted_args</replaceable>.
|
|
Unlike most built-in aggregates, these aggregates are not strict, that is
|
|
they do not drop input rows containing nulls. Null values sort according
|
|
to the rule specified in the <literal>ORDER BY</literal> clause.
|
|
</para>
|
|
|
|
<table id="functions-hypothetical-table">
|
|
<title>Hypothetical-Set Aggregate Functions</title>
|
|
<tgroup cols="2">
|
|
<colspec colname="col1" colwidth="10*"/>
|
|
<colspec colname="col2" colwidth="1*"/>
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
<entry>Partial Mode</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>rank</primary>
|
|
<secondary>hypothetical</secondary>
|
|
</indexterm>
|
|
<function>rank</function> ( <replaceable>args</replaceable> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <replaceable>sorted_args</replaceable> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the rank of the hypothetical row, with gaps; that is, the row
|
|
number of the first row in its peer group.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>dense_rank</primary>
|
|
<secondary>hypothetical</secondary>
|
|
</indexterm>
|
|
<function>dense_rank</function> ( <replaceable>args</replaceable> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <replaceable>sorted_args</replaceable> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the rank of the hypothetical row, without gaps; this function
|
|
effectively counts peer groups.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>percent_rank</primary>
|
|
<secondary>hypothetical</secondary>
|
|
</indexterm>
|
|
<function>percent_rank</function> ( <replaceable>args</replaceable> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <replaceable>sorted_args</replaceable> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the relative rank of the hypothetical row, that is
|
|
(<function>rank</function> - 1) / (total rows - 1).
|
|
The value thus ranges from 0 to 1 inclusive.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cume_dist</primary>
|
|
<secondary>hypothetical</secondary>
|
|
</indexterm>
|
|
<function>cume_dist</function> ( <replaceable>args</replaceable> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <replaceable>sorted_args</replaceable> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the cumulative distribution, that is (number of rows
|
|
preceding or peers with hypothetical row) / (total rows). The value
|
|
thus ranges from 1/<parameter>N</parameter> to 1.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-grouping-table">
|
|
<title>Grouping Operations</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>GROUPING</primary>
|
|
</indexterm>
|
|
<function>GROUPING</function> ( <replaceable>group_by_expression(s)</replaceable> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a bit mask indicating which <literal>GROUP BY</literal>
|
|
expressions are not included in the current grouping set.
|
|
Bits are assigned with the rightmost argument corresponding to the
|
|
least-significant bit; each bit is 0 if the corresponding expression
|
|
is included in the grouping criteria of the grouping set generating
|
|
the current result row, and 1 if it is not included.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The grouping operations shown in
|
|
<xref linkend="functions-grouping-table"/> are used in conjunction with
|
|
grouping sets (see <xref linkend="queries-grouping-sets"/>) to distinguish
|
|
result rows. The arguments to the <literal>GROUPING</literal> function
|
|
are not actually evaluated, but they must exactly match expressions given
|
|
in the <literal>GROUP BY</literal> clause of the associated query level.
|
|
For example:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>SELECT * FROM items_sold;</userinput>
|
|
make | model | sales
|
|
-------+-------+-------
|
|
Foo | GT | 10
|
|
Foo | Tour | 20
|
|
Bar | City | 15
|
|
Bar | Sport | 5
|
|
(4 rows)
|
|
|
|
<prompt>=></prompt> <userinput>SELECT make, model, GROUPING(make,model), sum(sales) FROM items_sold GROUP BY ROLLUP(make,model);</userinput>
|
|
make | model | grouping | sum
|
|
-------+-------+----------+-----
|
|
Foo | GT | 0 | 10
|
|
Foo | Tour | 0 | 20
|
|
Bar | City | 0 | 15
|
|
Bar | Sport | 0 | 5
|
|
Foo | | 1 | 30
|
|
Bar | | 1 | 20
|
|
| | 3 | 50
|
|
(7 rows)
|
|
</screen>
|
|
Here, the <literal>grouping</literal> value <literal>0</literal> in the
|
|
first four rows shows that those have been grouped normally, over both the
|
|
grouping columns. The value <literal>1</literal> indicates
|
|
that <literal>model</literal> was not grouped by in the next-to-last two
|
|
rows, and the value <literal>3</literal> indicates that
|
|
neither <literal>make</literal> nor <literal>model</literal> was grouped
|
|
by in the last row (which therefore is an aggregate over all the input
|
|
rows).
|
|
</para>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="functions-window">
|
|
<title>Window Functions</title>
|
|
|
|
<indexterm zone="functions-window">
|
|
<primary>window function</primary>
|
|
<secondary>built-in</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<firstterm>Window functions</firstterm> provide the ability to perform
|
|
calculations across sets of rows that are related to the current query
|
|
row. See <xref linkend="tutorial-window"/> for an introduction to this
|
|
feature, and <xref linkend="syntax-window-functions"/> for syntax
|
|
details.
|
|
</para>
|
|
|
|
<para>
|
|
The built-in window functions are listed in
|
|
<xref linkend="functions-window-table"/>. Note that these functions
|
|
<emphasis>must</emphasis> be invoked using window function syntax, i.e., an
|
|
<literal>OVER</literal> clause is required.
|
|
</para>
|
|
|
|
<para>
|
|
In addition to these functions, any built-in or user-defined
|
|
ordinary aggregate (i.e., not ordered-set or hypothetical-set aggregates)
|
|
can be used as a window function; see
|
|
<xref linkend="functions-aggregate"/> for a list of the built-in aggregates.
|
|
Aggregate functions act as window functions only when an <literal>OVER</literal>
|
|
clause follows the call; otherwise they act as plain aggregates
|
|
and return a single row for the entire set.
|
|
</para>
|
|
|
|
<table id="functions-window-table">
|
|
<title>General-Purpose Window Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>row_number</primary>
|
|
</indexterm>
|
|
<function>row_number</function> ()
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of the current row within its partition, counting
|
|
from 1.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>rank</primary>
|
|
</indexterm>
|
|
<function>rank</function> ()
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the rank of the current row, with gaps; that is,
|
|
the <function>row_number</function> of the first row in its peer
|
|
group.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>dense_rank</primary>
|
|
</indexterm>
|
|
<function>dense_rank</function> ()
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the rank of the current row, without gaps; this function
|
|
effectively counts peer groups.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>percent_rank</primary>
|
|
</indexterm>
|
|
<function>percent_rank</function> ()
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the relative rank of the current row, that is
|
|
(<function>rank</function> - 1) / (total partition rows - 1).
|
|
The value thus ranges from 0 to 1 inclusive.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cume_dist</primary>
|
|
</indexterm>
|
|
<function>cume_dist</function> ()
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the cumulative distribution, that is (number of partition rows
|
|
preceding or peers with current row) / (total partition rows).
|
|
The value thus ranges from 1/<parameter>N</parameter> to 1.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>ntile</primary>
|
|
</indexterm>
|
|
<function>ntile</function> ( <parameter>num_buckets</parameter> <type>integer</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an integer ranging from 1 to the argument value, dividing the
|
|
partition as equally as possible.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lag</primary>
|
|
</indexterm>
|
|
<function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
|
|
<optional>, <parameter>offset</parameter> <type>integer</type>
|
|
<optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
|
|
<returnvalue>anycompatible</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns <parameter>value</parameter> evaluated at
|
|
the row that is <parameter>offset</parameter>
|
|
rows before the current row within the partition; if there is no such
|
|
row, instead returns <parameter>default</parameter>
|
|
(which must be of a type compatible with
|
|
<parameter>value</parameter>).
|
|
Both <parameter>offset</parameter> and
|
|
<parameter>default</parameter> are evaluated
|
|
with respect to the current row. If omitted,
|
|
<parameter>offset</parameter> defaults to 1 and
|
|
<parameter>default</parameter> to <literal>NULL</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>lead</primary>
|
|
</indexterm>
|
|
<function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
|
|
<optional>, <parameter>offset</parameter> <type>integer</type>
|
|
<optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
|
|
<returnvalue>anycompatible</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns <parameter>value</parameter> evaluated at
|
|
the row that is <parameter>offset</parameter>
|
|
rows after the current row within the partition; if there is no such
|
|
row, instead returns <parameter>default</parameter>
|
|
(which must be of a type compatible with
|
|
<parameter>value</parameter>).
|
|
Both <parameter>offset</parameter> and
|
|
<parameter>default</parameter> are evaluated
|
|
with respect to the current row. If omitted,
|
|
<parameter>offset</parameter> defaults to 1 and
|
|
<parameter>default</parameter> to <literal>NULL</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>first_value</primary>
|
|
</indexterm>
|
|
<function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns <parameter>value</parameter> evaluated
|
|
at the row that is the first row of the window frame.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>last_value</primary>
|
|
</indexterm>
|
|
<function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns <parameter>value</parameter> evaluated
|
|
at the row that is the last row of the window frame.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>nth_value</primary>
|
|
</indexterm>
|
|
<function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns <parameter>value</parameter> evaluated
|
|
at the row that is the <parameter>n</parameter>'th
|
|
row of the window frame (counting from 1);
|
|
returns <literal>NULL</literal> if there is no such row.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
All of the functions listed in
|
|
<xref linkend="functions-window-table"/> depend on the sort ordering
|
|
specified by the <literal>ORDER BY</literal> clause of the associated window
|
|
definition. Rows that are not distinct when considering only the
|
|
<literal>ORDER BY</literal> columns are said to be <firstterm>peers</firstterm>.
|
|
The four ranking functions (including <function>cume_dist</function>) are
|
|
defined so that they give the same answer for all rows of a peer group.
|
|
</para>
|
|
|
|
<para>
|
|
Note that <function>first_value</function>, <function>last_value</function>, and
|
|
<function>nth_value</function> consider only the rows within the <quote>window
|
|
frame</quote>, which by default contains the rows from the start of the
|
|
partition through the last peer of the current row. This is
|
|
likely to give unhelpful results for <function>last_value</function> and
|
|
sometimes also <function>nth_value</function>. You can redefine the frame by
|
|
adding a suitable frame specification (<literal>RANGE</literal>,
|
|
<literal>ROWS</literal> or <literal>GROUPS</literal>) to
|
|
the <literal>OVER</literal> clause.
|
|
See <xref linkend="syntax-window-functions"/> for more information
|
|
about frame specifications.
|
|
</para>
|
|
|
|
<para>
|
|
When an aggregate function is used as a window function, it aggregates
|
|
over the rows within the current row's window frame.
|
|
An aggregate used with <literal>ORDER BY</literal> and the default window frame
|
|
definition produces a <quote>running sum</quote> type of behavior, which may or
|
|
may not be what's wanted. To obtain
|
|
aggregation over the whole partition, omit <literal>ORDER BY</literal> or use
|
|
<literal>ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING</literal>.
|
|
Other frame specifications can be used to obtain other effects.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
The SQL standard defines a <literal>RESPECT NULLS</literal> or
|
|
<literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
|
|
<function>first_value</function>, <function>last_value</function>, and
|
|
<function>nth_value</function>. This is not implemented in
|
|
<productname>PostgreSQL</productname>: the behavior is always the
|
|
same as the standard's default, namely <literal>RESPECT NULLS</literal>.
|
|
Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
|
|
option for <function>nth_value</function> is not implemented: only the
|
|
default <literal>FROM FIRST</literal> behavior is supported. (You can achieve
|
|
the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
|
|
ordering.)
|
|
</para>
|
|
</note>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="functions-merge-support">
|
|
<title>Merge Support Functions</title>
|
|
|
|
<indexterm>
|
|
<primary>MERGE</primary>
|
|
<secondary>RETURNING</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> includes one merge support function
|
|
that may be used in the <literal>RETURNING</literal> list of a
|
|
<xref linkend="sql-merge"/> command to identify the action taken for each
|
|
row; see <xref linkend="functions-merge-support-table"/>.
|
|
</para>
|
|
|
|
<table id="functions-merge-support-table">
|
|
<title>Merge Support Functions</title>
|
|
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry id="merge-action" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>merge_action</primary>
|
|
</indexterm>
|
|
<function>merge_action</function> ( )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the merge action command executed for the current row. This
|
|
will be <literal>'INSERT'</literal>, <literal>'UPDATE'</literal>, or
|
|
<literal>'DELETE'</literal>.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Example:
|
|
<screen><![CDATA[
|
|
MERGE INTO products p
|
|
USING stock s ON p.product_id = s.product_id
|
|
WHEN MATCHED AND s.quantity > 0 THEN
|
|
UPDATE SET in_stock = true, quantity = s.quantity
|
|
WHEN MATCHED THEN
|
|
UPDATE SET in_stock = false, quantity = 0
|
|
WHEN NOT MATCHED THEN
|
|
INSERT (product_id, in_stock, quantity)
|
|
VALUES (s.product_id, true, s.quantity)
|
|
RETURNING merge_action(), p.*;
|
|
|
|
merge_action | product_id | in_stock | quantity
|
|
--------------+------------+----------+----------
|
|
UPDATE | 1001 | t | 50
|
|
UPDATE | 1002 | f | 0
|
|
INSERT | 1003 | t | 10
|
|
]]></screen>
|
|
</para>
|
|
|
|
<para>
|
|
Note that this function can only be used in the <literal>RETURNING</literal>
|
|
list of a <command>MERGE</command> command. It is an error to use it in any
|
|
other part of a query.
|
|
</para>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="functions-subquery">
|
|
<title>Subquery Expressions</title>
|
|
|
|
<indexterm>
|
|
<primary>EXISTS</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>IN</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>NOT IN</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>ANY</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>ALL</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>SOME</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>subquery</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
This section describes the <acronym>SQL</acronym>-compliant subquery
|
|
expressions available in <productname>PostgreSQL</productname>.
|
|
All of the expression forms documented in this section return
|
|
Boolean (true/false) results.
|
|
</para>
|
|
|
|
<sect2 id="functions-subquery-exists">
|
|
<title><literal>EXISTS</literal></title>
|
|
|
|
<synopsis>
|
|
EXISTS (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The argument of <token>EXISTS</token> is an arbitrary <command>SELECT</command> statement,
|
|
or <firstterm>subquery</firstterm>. The
|
|
subquery is evaluated to determine whether it returns any rows.
|
|
If it returns at least one row, the result of <token>EXISTS</token> is
|
|
<quote>true</quote>; if the subquery returns no rows, the result of <token>EXISTS</token>
|
|
is <quote>false</quote>.
|
|
</para>
|
|
|
|
<para>
|
|
The subquery can refer to variables from the surrounding query,
|
|
which will act as constants during any one evaluation of the subquery.
|
|
</para>
|
|
|
|
<para>
|
|
The subquery will generally only be executed long enough to determine
|
|
whether at least one row is returned, not all the way to completion.
|
|
It is unwise to write a subquery that has side effects (such as
|
|
calling sequence functions); whether the side effects occur
|
|
might be unpredictable.
|
|
</para>
|
|
|
|
<para>
|
|
Since the result depends only on whether any rows are returned,
|
|
and not on the contents of those rows, the output list of the
|
|
subquery is normally unimportant. A common coding convention is
|
|
to write all <literal>EXISTS</literal> tests in the form
|
|
<literal>EXISTS(SELECT 1 WHERE ...)</literal>. There are exceptions to
|
|
this rule however, such as subqueries that use <token>INTERSECT</token>.
|
|
</para>
|
|
|
|
<para>
|
|
This simple example is like an inner join on <literal>col2</literal>, but
|
|
it produces at most one output row for each <literal>tab1</literal> row,
|
|
even if there are several matching <literal>tab2</literal> rows:
|
|
<screen>
|
|
SELECT col1
|
|
FROM tab1
|
|
WHERE EXISTS (SELECT 1 FROM tab2 WHERE col2 = tab1.col2);
|
|
</screen>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-subquery-in">
|
|
<title><literal>IN</literal></title>
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> IN (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The right-hand side is a parenthesized
|
|
subquery, which must return exactly one column. The left-hand expression
|
|
is evaluated and compared to each row of the subquery result.
|
|
The result of <token>IN</token> is <quote>true</quote> if any equal subquery row is found.
|
|
The result is <quote>false</quote> if no equal row is found (including the
|
|
case where the subquery returns no rows).
|
|
</para>
|
|
|
|
<para>
|
|
Note that if the left-hand expression yields null, or if there are
|
|
no equal right-hand values and at least one right-hand row yields
|
|
null, the result of the <token>IN</token> construct will be null, not false.
|
|
This is in accordance with SQL's normal rules for Boolean combinations
|
|
of null values.
|
|
</para>
|
|
|
|
<para>
|
|
As with <token>EXISTS</token>, it's unwise to assume that the subquery will
|
|
be evaluated completely.
|
|
</para>
|
|
|
|
<synopsis>
|
|
<replaceable>row_constructor</replaceable> IN (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The left-hand side of this form of <token>IN</token> is a row constructor,
|
|
as described in <xref linkend="sql-syntax-row-constructors"/>.
|
|
The right-hand side is a parenthesized
|
|
subquery, which must return exactly as many columns as there are
|
|
expressions in the left-hand row. The left-hand expressions are
|
|
evaluated and compared row-wise to each row of the subquery result.
|
|
The result of <token>IN</token> is <quote>true</quote> if any equal subquery row is found.
|
|
The result is <quote>false</quote> if no equal row is found (including the
|
|
case where the subquery returns no rows).
|
|
</para>
|
|
|
|
<para>
|
|
As usual, null values in the rows are combined per
|
|
the normal rules of SQL Boolean expressions. Two rows are considered
|
|
equal if all their corresponding members are non-null and equal; the rows
|
|
are unequal if any corresponding members are non-null and unequal;
|
|
otherwise the result of that row comparison is unknown (null).
|
|
If all the per-row results are either unequal or null, with at least one
|
|
null, then the result of <token>IN</token> is null.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-subquery-notin">
|
|
<title><literal>NOT IN</literal></title>
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> NOT IN (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The right-hand side is a parenthesized
|
|
subquery, which must return exactly one column. The left-hand expression
|
|
is evaluated and compared to each row of the subquery result.
|
|
The result of <token>NOT IN</token> is <quote>true</quote> if only unequal subquery rows
|
|
are found (including the case where the subquery returns no rows).
|
|
The result is <quote>false</quote> if any equal row is found.
|
|
</para>
|
|
|
|
<para>
|
|
Note that if the left-hand expression yields null, or if there are
|
|
no equal right-hand values and at least one right-hand row yields
|
|
null, the result of the <token>NOT IN</token> construct will be null, not true.
|
|
This is in accordance with SQL's normal rules for Boolean combinations
|
|
of null values.
|
|
</para>
|
|
|
|
<para>
|
|
As with <token>EXISTS</token>, it's unwise to assume that the subquery will
|
|
be evaluated completely.
|
|
</para>
|
|
|
|
<synopsis>
|
|
<replaceable>row_constructor</replaceable> NOT IN (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The left-hand side of this form of <token>NOT IN</token> is a row constructor,
|
|
as described in <xref linkend="sql-syntax-row-constructors"/>.
|
|
The right-hand side is a parenthesized
|
|
subquery, which must return exactly as many columns as there are
|
|
expressions in the left-hand row. The left-hand expressions are
|
|
evaluated and compared row-wise to each row of the subquery result.
|
|
The result of <token>NOT IN</token> is <quote>true</quote> if only unequal subquery rows
|
|
are found (including the case where the subquery returns no rows).
|
|
The result is <quote>false</quote> if any equal row is found.
|
|
</para>
|
|
|
|
<para>
|
|
As usual, null values in the rows are combined per
|
|
the normal rules of SQL Boolean expressions. Two rows are considered
|
|
equal if all their corresponding members are non-null and equal; the rows
|
|
are unequal if any corresponding members are non-null and unequal;
|
|
otherwise the result of that row comparison is unknown (null).
|
|
If all the per-row results are either unequal or null, with at least one
|
|
null, then the result of <token>NOT IN</token> is null.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-subquery-any-some">
|
|
<title><literal>ANY</literal>/<literal>SOME</literal></title>
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> <replaceable>operator</replaceable> ANY (<replaceable>subquery</replaceable>)
|
|
<replaceable>expression</replaceable> <replaceable>operator</replaceable> SOME (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The right-hand side is a parenthesized
|
|
subquery, which must return exactly one column. The left-hand expression
|
|
is evaluated and compared to each row of the subquery result using the
|
|
given <replaceable>operator</replaceable>, which must yield a Boolean
|
|
result.
|
|
The result of <token>ANY</token> is <quote>true</quote> if any true result is obtained.
|
|
The result is <quote>false</quote> if no true result is found (including the
|
|
case where the subquery returns no rows).
|
|
</para>
|
|
|
|
<para>
|
|
<token>SOME</token> is a synonym for <token>ANY</token>.
|
|
<token>IN</token> is equivalent to <literal>= ANY</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
Note that if there are no successes and at least one right-hand row yields
|
|
null for the operator's result, the result of the <token>ANY</token> construct
|
|
will be null, not false.
|
|
This is in accordance with SQL's normal rules for Boolean combinations
|
|
of null values.
|
|
</para>
|
|
|
|
<para>
|
|
As with <token>EXISTS</token>, it's unwise to assume that the subquery will
|
|
be evaluated completely.
|
|
</para>
|
|
|
|
<synopsis>
|
|
<replaceable>row_constructor</replaceable> <replaceable>operator</replaceable> ANY (<replaceable>subquery</replaceable>)
|
|
<replaceable>row_constructor</replaceable> <replaceable>operator</replaceable> SOME (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The left-hand side of this form of <token>ANY</token> is a row constructor,
|
|
as described in <xref linkend="sql-syntax-row-constructors"/>.
|
|
The right-hand side is a parenthesized
|
|
subquery, which must return exactly as many columns as there are
|
|
expressions in the left-hand row. The left-hand expressions are
|
|
evaluated and compared row-wise to each row of the subquery result,
|
|
using the given <replaceable>operator</replaceable>.
|
|
The result of <token>ANY</token> is <quote>true</quote> if the comparison
|
|
returns true for any subquery row.
|
|
The result is <quote>false</quote> if the comparison returns false for every
|
|
subquery row (including the case where the subquery returns no
|
|
rows).
|
|
The result is NULL if no comparison with a subquery row returns true,
|
|
and at least one comparison returns NULL.
|
|
</para>
|
|
|
|
<para>
|
|
See <xref linkend="row-wise-comparison"/> for details about the meaning
|
|
of a row constructor comparison.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-subquery-all">
|
|
<title><literal>ALL</literal></title>
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> <replaceable>operator</replaceable> ALL (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The right-hand side is a parenthesized
|
|
subquery, which must return exactly one column. The left-hand expression
|
|
is evaluated and compared to each row of the subquery result using the
|
|
given <replaceable>operator</replaceable>, which must yield a Boolean
|
|
result.
|
|
The result of <token>ALL</token> is <quote>true</quote> if all rows yield true
|
|
(including the case where the subquery returns no rows).
|
|
The result is <quote>false</quote> if any false result is found.
|
|
The result is NULL if no comparison with a subquery row returns false,
|
|
and at least one comparison returns NULL.
|
|
</para>
|
|
|
|
<para>
|
|
<token>NOT IN</token> is equivalent to <literal><> ALL</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
As with <token>EXISTS</token>, it's unwise to assume that the subquery will
|
|
be evaluated completely.
|
|
</para>
|
|
|
|
<synopsis>
|
|
<replaceable>row_constructor</replaceable> <replaceable>operator</replaceable> ALL (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The left-hand side of this form of <token>ALL</token> is a row constructor,
|
|
as described in <xref linkend="sql-syntax-row-constructors"/>.
|
|
The right-hand side is a parenthesized
|
|
subquery, which must return exactly as many columns as there are
|
|
expressions in the left-hand row. The left-hand expressions are
|
|
evaluated and compared row-wise to each row of the subquery result,
|
|
using the given <replaceable>operator</replaceable>.
|
|
The result of <token>ALL</token> is <quote>true</quote> if the comparison
|
|
returns true for all subquery rows (including the
|
|
case where the subquery returns no rows).
|
|
The result is <quote>false</quote> if the comparison returns false for any
|
|
subquery row.
|
|
The result is NULL if no comparison with a subquery row returns false,
|
|
and at least one comparison returns NULL.
|
|
</para>
|
|
|
|
<para>
|
|
See <xref linkend="row-wise-comparison"/> for details about the meaning
|
|
of a row constructor comparison.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-subquery-single-row-comp">
|
|
<title>Single-Row Comparison</title>
|
|
|
|
<indexterm zone="functions-subquery">
|
|
<primary>comparison</primary>
|
|
<secondary>subquery result row</secondary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<replaceable>row_constructor</replaceable> <replaceable>operator</replaceable> (<replaceable>subquery</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The left-hand side is a row constructor,
|
|
as described in <xref linkend="sql-syntax-row-constructors"/>.
|
|
The right-hand side is a parenthesized subquery, which must return exactly
|
|
as many columns as there are expressions in the left-hand row. Furthermore,
|
|
the subquery cannot return more than one row. (If it returns zero rows,
|
|
the result is taken to be null.) The left-hand side is evaluated and
|
|
compared row-wise to the single subquery result row.
|
|
</para>
|
|
|
|
<para>
|
|
See <xref linkend="row-wise-comparison"/> for details about the meaning
|
|
of a row constructor comparison.
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="functions-comparisons">
|
|
<title>Row and Array Comparisons</title>
|
|
|
|
<indexterm>
|
|
<primary>IN</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>NOT IN</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>ANY</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>ALL</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>SOME</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>composite type</primary>
|
|
<secondary>comparison</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>row-wise comparison</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>comparison</primary>
|
|
<secondary>composite type</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>comparison</primary>
|
|
<secondary>row constructor</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>IS DISTINCT FROM</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>IS NOT DISTINCT FROM</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
This section describes several specialized constructs for making
|
|
multiple comparisons between groups of values. These forms are
|
|
syntactically related to the subquery forms of the previous section,
|
|
but do not involve subqueries.
|
|
The forms involving array subexpressions are
|
|
<productname>PostgreSQL</productname> extensions; the rest are
|
|
<acronym>SQL</acronym>-compliant.
|
|
All of the expression forms documented in this section return
|
|
Boolean (true/false) results.
|
|
</para>
|
|
|
|
<sect2 id="functions-comparisons-in-scalar">
|
|
<title><literal>IN</literal></title>
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> IN (<replaceable>value</replaceable> <optional>, ...</optional>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The right-hand side is a parenthesized list
|
|
of expressions. The result is <quote>true</quote> if the left-hand expression's
|
|
result is equal to any of the right-hand expressions. This is a shorthand
|
|
notation for
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> = <replaceable>value1</replaceable>
|
|
OR
|
|
<replaceable>expression</replaceable> = <replaceable>value2</replaceable>
|
|
OR
|
|
...
|
|
</synopsis>
|
|
</para>
|
|
|
|
<para>
|
|
Note that if the left-hand expression yields null, or if there are
|
|
no equal right-hand values and at least one right-hand expression yields
|
|
null, the result of the <token>IN</token> construct will be null, not false.
|
|
This is in accordance with SQL's normal rules for Boolean combinations
|
|
of null values.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-comparisons-not-in">
|
|
<title><literal>NOT IN</literal></title>
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> NOT IN (<replaceable>value</replaceable> <optional>, ...</optional>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The right-hand side is a parenthesized list
|
|
of expressions. The result is <quote>true</quote> if the left-hand expression's
|
|
result is unequal to all of the right-hand expressions. This is a shorthand
|
|
notation for
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> <> <replaceable>value1</replaceable>
|
|
AND
|
|
<replaceable>expression</replaceable> <> <replaceable>value2</replaceable>
|
|
AND
|
|
...
|
|
</synopsis>
|
|
</para>
|
|
|
|
<para>
|
|
Note that if the left-hand expression yields null, or if there are
|
|
no equal right-hand values and at least one right-hand expression yields
|
|
null, the result of the <token>NOT IN</token> construct will be null, not true
|
|
as one might naively expect.
|
|
This is in accordance with SQL's normal rules for Boolean combinations
|
|
of null values.
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
<literal>x NOT IN y</literal> is equivalent to <literal>NOT (x IN y)</literal> in all
|
|
cases. However, null values are much more likely to trip up the novice when
|
|
working with <token>NOT IN</token> than when working with <token>IN</token>.
|
|
It is best to express your condition positively if possible.
|
|
</para>
|
|
</tip>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-comparisons-any-some">
|
|
<title><literal>ANY</literal>/<literal>SOME</literal> (array)</title>
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> <replaceable>operator</replaceable> ANY (<replaceable>array expression</replaceable>)
|
|
<replaceable>expression</replaceable> <replaceable>operator</replaceable> SOME (<replaceable>array expression</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The right-hand side is a parenthesized expression, which must yield an
|
|
array value.
|
|
The left-hand expression
|
|
is evaluated and compared to each element of the array using the
|
|
given <replaceable>operator</replaceable>, which must yield a Boolean
|
|
result.
|
|
The result of <token>ANY</token> is <quote>true</quote> if any true result is obtained.
|
|
The result is <quote>false</quote> if no true result is found (including the
|
|
case where the array has zero elements).
|
|
</para>
|
|
|
|
<para>
|
|
If the array expression yields a null array, the result of
|
|
<token>ANY</token> will be null. If the left-hand expression yields null,
|
|
the result of <token>ANY</token> is ordinarily null (though a non-strict
|
|
comparison operator could possibly yield a different result).
|
|
Also, if the right-hand array contains any null elements and no true
|
|
comparison result is obtained, the result of <token>ANY</token>
|
|
will be null, not false (again, assuming a strict comparison operator).
|
|
This is in accordance with SQL's normal rules for Boolean combinations
|
|
of null values.
|
|
</para>
|
|
|
|
<para>
|
|
<token>SOME</token> is a synonym for <token>ANY</token>.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="functions-comparisons-all">
|
|
<title><literal>ALL</literal> (array)</title>
|
|
|
|
<synopsis>
|
|
<replaceable>expression</replaceable> <replaceable>operator</replaceable> ALL (<replaceable>array expression</replaceable>)
|
|
</synopsis>
|
|
|
|
<para>
|
|
The right-hand side is a parenthesized expression, which must yield an
|
|
array value.
|
|
The left-hand expression
|
|
is evaluated and compared to each element of the array using the
|
|
given <replaceable>operator</replaceable>, which must yield a Boolean
|
|
result.
|
|
The result of <token>ALL</token> is <quote>true</quote> if all comparisons yield true
|
|
(including the case where the array has zero elements).
|
|
The result is <quote>false</quote> if any false result is found.
|
|
</para>
|
|
|
|
<para>
|
|
If the array expression yields a null array, the result of
|
|
<token>ALL</token> will be null. If the left-hand expression yields null,
|
|
the result of <token>ALL</token> is ordinarily null (though a non-strict
|
|
comparison operator could possibly yield a different result).
|
|
Also, if the right-hand array contains any null elements and no false
|
|
comparison result is obtained, the result of <token>ALL</token>
|
|
will be null, not true (again, assuming a strict comparison operator).
|
|
This is in accordance with SQL's normal rules for Boolean combinations
|
|
of null values.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="row-wise-comparison">
|
|
<title>Row Constructor Comparison</title>
|
|
|
|
<synopsis>
|
|
<replaceable>row_constructor</replaceable> <replaceable>operator</replaceable> <replaceable>row_constructor</replaceable>
|
|
</synopsis>
|
|
|
|
<para>
|
|
Each side is a row constructor,
|
|
as described in <xref linkend="sql-syntax-row-constructors"/>.
|
|
The two row constructors must have the same number of fields.
|
|
The given <replaceable>operator</replaceable> is applied to each pair
|
|
of corresponding fields. (Since the fields could be of different
|
|
types, this means that a different specific operator could be selected
|
|
for each pair.)
|
|
All the selected operators must be members of some B-tree operator
|
|
class, or be the negator of an <literal>=</literal> member of a B-tree
|
|
operator class, meaning that row constructor comparison is only
|
|
possible when the <replaceable>operator</replaceable> is
|
|
<literal>=</literal>,
|
|
<literal><></literal>,
|
|
<literal><</literal>,
|
|
<literal><=</literal>,
|
|
<literal>></literal>, or
|
|
<literal>>=</literal>,
|
|
or has semantics similar to one of these.
|
|
</para>
|
|
|
|
<para>
|
|
The <literal>=</literal> and <literal><></literal> cases work slightly differently
|
|
from the others. Two rows are considered
|
|
equal if all their corresponding members are non-null and equal; the rows
|
|
are unequal if any corresponding members are non-null and unequal;
|
|
otherwise the result of the row comparison is unknown (null).
|
|
</para>
|
|
|
|
<para>
|
|
For the <literal><</literal>, <literal><=</literal>, <literal>></literal> and
|
|
<literal>>=</literal> cases, the row elements are compared left-to-right,
|
|
stopping as soon as an unequal or null pair of elements is found.
|
|
If either of this pair of elements is null, the result of the
|
|
row comparison is unknown (null); otherwise comparison of this pair
|
|
of elements determines the result. For example,
|
|
<literal>ROW(1,2,NULL) < ROW(1,3,0)</literal>
|
|
yields true, not null, because the third pair of elements are not
|
|
considered.
|
|
</para>
|
|
|
|
<synopsis>
|
|
<replaceable>row_constructor</replaceable> IS DISTINCT FROM <replaceable>row_constructor</replaceable>
|
|
</synopsis>
|
|
|
|
<para>
|
|
This construct is similar to a <literal><></literal> row comparison,
|
|
but it does not yield null for null inputs. Instead, any null value is
|
|
considered unequal to (distinct from) any non-null value, and any two
|
|
nulls are considered equal (not distinct). Thus the result will
|
|
either be true or false, never null.
|
|
</para>
|
|
|
|
<synopsis>
|
|
<replaceable>row_constructor</replaceable> IS NOT DISTINCT FROM <replaceable>row_constructor</replaceable>
|
|
</synopsis>
|
|
|
|
<para>
|
|
This construct is similar to a <literal>=</literal> row comparison,
|
|
but it does not yield null for null inputs. Instead, any null value is
|
|
considered unequal to (distinct from) any non-null value, and any two
|
|
nulls are considered equal (not distinct). Thus the result will always
|
|
be either true or false, never null.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="composite-type-comparison">
|
|
<title>Composite Type Comparison</title>
|
|
|
|
<synopsis>
|
|
<replaceable>record</replaceable> <replaceable>operator</replaceable> <replaceable>record</replaceable>
|
|
</synopsis>
|
|
|
|
<para>
|
|
The SQL specification requires row-wise comparison to return NULL if the
|
|
result depends on comparing two NULL values or a NULL and a non-NULL.
|
|
<productname>PostgreSQL</productname> does this only when comparing the
|
|
results of two row constructors (as in
|
|
<xref linkend="row-wise-comparison"/>) or comparing a row constructor
|
|
to the output of a subquery (as in <xref linkend="functions-subquery"/>).
|
|
In other contexts where two composite-type values are compared, two
|
|
NULL field values are considered equal, and a NULL is considered larger
|
|
than a non-NULL. This is necessary in order to have consistent sorting
|
|
and indexing behavior for composite types.
|
|
</para>
|
|
|
|
<para>
|
|
Each side is evaluated and they are compared row-wise. Composite type
|
|
comparisons are allowed when the <replaceable>operator</replaceable> is
|
|
<literal>=</literal>,
|
|
<literal><></literal>,
|
|
<literal><</literal>,
|
|
<literal><=</literal>,
|
|
<literal>></literal> or
|
|
<literal>>=</literal>,
|
|
or has semantics similar to one of these. (To be specific, an operator
|
|
can be a row comparison operator if it is a member of a B-tree operator
|
|
class, or is the negator of the <literal>=</literal> member of a B-tree operator
|
|
class.) The default behavior of the above operators is the same as for
|
|
<literal>IS [ NOT ] DISTINCT FROM</literal> for row constructors (see
|
|
<xref linkend="row-wise-comparison"/>).
|
|
</para>
|
|
|
|
<para>
|
|
To support matching of rows which include elements without a default
|
|
B-tree operator class, the following operators are defined for composite
|
|
type comparison:
|
|
<literal>*=</literal>,
|
|
<literal>*<></literal>,
|
|
<literal>*<</literal>,
|
|
<literal>*<=</literal>,
|
|
<literal>*></literal>, and
|
|
<literal>*>=</literal>.
|
|
These operators compare the internal binary representation of the two
|
|
rows. Two rows might have a different binary representation even
|
|
though comparisons of the two rows with the equality operator is true.
|
|
The ordering of rows under these comparison operators is deterministic
|
|
but not otherwise meaningful. These operators are used internally
|
|
for materialized views and might be useful for other specialized
|
|
purposes such as replication and B-Tree deduplication (see <xref
|
|
linkend="btree-deduplication"/>). They are not intended to be
|
|
generally useful for writing queries, though.
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-srf">
|
|
<title>Set Returning Functions</title>
|
|
|
|
<indexterm zone="functions-srf">
|
|
<primary>set returning functions</primary>
|
|
<secondary>functions</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
This section describes functions that possibly return more than one row.
|
|
The most widely used functions in this class are series generating
|
|
functions, as detailed in <xref linkend="functions-srf-series"/> and
|
|
<xref linkend="functions-srf-subscripts"/>. Other, more specialized
|
|
set-returning functions are described elsewhere in this manual.
|
|
See <xref linkend="queries-tablefunctions"/> for ways to combine multiple
|
|
set-returning functions.
|
|
</para>
|
|
|
|
<table id="functions-srf-series">
|
|
<title>Series Generating Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>generate_series</primary>
|
|
</indexterm>
|
|
<function>generate_series</function> ( <parameter>start</parameter> <type>integer</type>, <parameter>stop</parameter> <type>integer</type> <optional>, <parameter>step</parameter> <type>integer</type> </optional> )
|
|
<returnvalue>setof integer</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>generate_series</function> ( <parameter>start</parameter> <type>bigint</type>, <parameter>stop</parameter> <type>bigint</type> <optional>, <parameter>step</parameter> <type>bigint</type> </optional> )
|
|
<returnvalue>setof bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>generate_series</function> ( <parameter>start</parameter> <type>numeric</type>, <parameter>stop</parameter> <type>numeric</type> <optional>, <parameter>step</parameter> <type>numeric</type> </optional> )
|
|
<returnvalue>setof numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Generates a series of values from <parameter>start</parameter>
|
|
to <parameter>stop</parameter>, with a step size
|
|
of <parameter>step</parameter>. <parameter>step</parameter>
|
|
defaults to 1.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>generate_series</function> ( <parameter>start</parameter> <type>timestamp</type>, <parameter>stop</parameter> <type>timestamp</type>, <parameter>step</parameter> <type>interval</type> )
|
|
<returnvalue>setof timestamp</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>generate_series</function> ( <parameter>start</parameter> <type>timestamp with time zone</type>, <parameter>stop</parameter> <type>timestamp with time zone</type>, <parameter>step</parameter> <type>interval</type> <optional>, <parameter>timezone</parameter> <type>text</type> </optional> )
|
|
<returnvalue>setof timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Generates a series of values from <parameter>start</parameter>
|
|
to <parameter>stop</parameter>, with a step size
|
|
of <parameter>step</parameter>.
|
|
In the timezone-aware form, times of day and daylight-savings
|
|
adjustments are computed according to the time zone named by
|
|
the <parameter>timezone</parameter> argument, or the current
|
|
<xref linkend="guc-timezone"/> setting if that is omitted.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
When <parameter>step</parameter> is positive, zero rows are returned if
|
|
<parameter>start</parameter> is greater than <parameter>stop</parameter>.
|
|
Conversely, when <parameter>step</parameter> is negative, zero rows are
|
|
returned if <parameter>start</parameter> is less than <parameter>stop</parameter>.
|
|
Zero rows are also returned if any input is <literal>NULL</literal>.
|
|
It is an error
|
|
for <parameter>step</parameter> to be zero. Some examples follow:
|
|
<programlisting>
|
|
SELECT * FROM generate_series(2,4);
|
|
generate_series
|
|
-----------------
|
|
2
|
|
3
|
|
4
|
|
(3 rows)
|
|
|
|
SELECT * FROM generate_series(5,1,-2);
|
|
generate_series
|
|
-----------------
|
|
5
|
|
3
|
|
1
|
|
(3 rows)
|
|
|
|
SELECT * FROM generate_series(4,3);
|
|
generate_series
|
|
-----------------
|
|
(0 rows)
|
|
|
|
SELECT generate_series(1.1, 4, 1.3);
|
|
generate_series
|
|
-----------------
|
|
1.1
|
|
2.4
|
|
3.7
|
|
(3 rows)
|
|
|
|
-- this example relies on the date-plus-integer operator:
|
|
SELECT current_date + s.a AS dates FROM generate_series(0,14,7) AS s(a);
|
|
dates
|
|
------------
|
|
2004-02-05
|
|
2004-02-12
|
|
2004-02-19
|
|
(3 rows)
|
|
|
|
SELECT * FROM generate_series('2008-03-01 00:00'::timestamp,
|
|
'2008-03-04 12:00', '10 hours');
|
|
generate_series
|
|
---------------------
|
|
2008-03-01 00:00:00
|
|
2008-03-01 10:00:00
|
|
2008-03-01 20:00:00
|
|
2008-03-02 06:00:00
|
|
2008-03-02 16:00:00
|
|
2008-03-03 02:00:00
|
|
2008-03-03 12:00:00
|
|
2008-03-03 22:00:00
|
|
2008-03-04 08:00:00
|
|
(9 rows)
|
|
|
|
-- this example assumes that TimeZone is set to UTC; note the DST transition:
|
|
SELECT * FROM generate_series('2001-10-22 00:00 -04:00'::timestamptz,
|
|
'2001-11-01 00:00 -05:00'::timestamptz,
|
|
'1 day'::interval, 'America/New_York');
|
|
generate_series
|
|
------------------------
|
|
2001-10-22 04:00:00+00
|
|
2001-10-23 04:00:00+00
|
|
2001-10-24 04:00:00+00
|
|
2001-10-25 04:00:00+00
|
|
2001-10-26 04:00:00+00
|
|
2001-10-27 04:00:00+00
|
|
2001-10-28 04:00:00+00
|
|
2001-10-29 05:00:00+00
|
|
2001-10-30 05:00:00+00
|
|
2001-10-31 05:00:00+00
|
|
2001-11-01 05:00:00+00
|
|
(11 rows)
|
|
</programlisting>
|
|
</para>
|
|
|
|
<table id="functions-srf-subscripts">
|
|
<title>Subscript Generating Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>generate_subscripts</primary>
|
|
</indexterm>
|
|
<function>generate_subscripts</function> ( <parameter>array</parameter> <type>anyarray</type>, <parameter>dim</parameter> <type>integer</type> )
|
|
<returnvalue>setof integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Generates a series comprising the valid subscripts of
|
|
the <parameter>dim</parameter>'th dimension of the given array.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>generate_subscripts</function> ( <parameter>array</parameter> <type>anyarray</type>, <parameter>dim</parameter> <type>integer</type>, <parameter>reverse</parameter> <type>boolean</type> )
|
|
<returnvalue>setof integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Generates a series comprising the valid subscripts of
|
|
the <parameter>dim</parameter>'th dimension of the given array.
|
|
When <parameter>reverse</parameter> is true, returns the series in
|
|
reverse order.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<function>generate_subscripts</function> is a convenience function that generates
|
|
the set of valid subscripts for the specified dimension of the given
|
|
array.
|
|
Zero rows are returned for arrays that do not have the requested dimension,
|
|
or if any input is <literal>NULL</literal>.
|
|
Some examples follow:
|
|
<programlisting>
|
|
-- basic usage:
|
|
SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1) AS s;
|
|
s
|
|
---
|
|
1
|
|
2
|
|
3
|
|
4
|
|
(4 rows)
|
|
|
|
-- presenting an array, the subscript and the subscripted
|
|
-- value requires a subquery:
|
|
SELECT * FROM arrays;
|
|
a
|
|
--------------------
|
|
{-1,-2}
|
|
{100,200,300}
|
|
(2 rows)
|
|
|
|
SELECT a AS array, s AS subscript, a[s] AS value
|
|
FROM (SELECT generate_subscripts(a, 1) AS s, a FROM arrays) foo;
|
|
array | subscript | value
|
|
---------------+-----------+-------
|
|
{-1,-2} | 1 | -1
|
|
{-1,-2} | 2 | -2
|
|
{100,200,300} | 1 | 100
|
|
{100,200,300} | 2 | 200
|
|
{100,200,300} | 3 | 300
|
|
(5 rows)
|
|
|
|
-- unnest a 2D array:
|
|
CREATE OR REPLACE FUNCTION unnest2(anyarray)
|
|
RETURNS SETOF anyelement AS $$
|
|
select $1[i][j]
|
|
from generate_subscripts($1,1) g1(i),
|
|
generate_subscripts($1,2) g2(j);
|
|
$$ LANGUAGE sql IMMUTABLE;
|
|
CREATE FUNCTION
|
|
SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]);
|
|
unnest2
|
|
---------
|
|
1
|
|
2
|
|
3
|
|
4
|
|
(4 rows)
|
|
</programlisting>
|
|
</para>
|
|
|
|
<indexterm>
|
|
<primary>ordinality</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
When a function in the <literal>FROM</literal> clause is suffixed
|
|
by <literal>WITH ORDINALITY</literal>, a <type>bigint</type> column is
|
|
appended to the function's output column(s), which starts from 1 and
|
|
increments by 1 for each row of the function's output.
|
|
This is most useful in the case of set returning
|
|
functions such as <function>unnest()</function>.
|
|
|
|
<programlisting>
|
|
-- set returning function WITH ORDINALITY:
|
|
SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
|
|
ls | n
|
|
-----------------+----
|
|
pg_serial | 1
|
|
pg_twophase | 2
|
|
postmaster.opts | 3
|
|
pg_notify | 4
|
|
postgresql.conf | 5
|
|
pg_tblspc | 6
|
|
logfile | 7
|
|
base | 8
|
|
postmaster.pid | 9
|
|
pg_ident.conf | 10
|
|
global | 11
|
|
pg_xact | 12
|
|
pg_snapshots | 13
|
|
pg_multixact | 14
|
|
PG_VERSION | 15
|
|
pg_wal | 16
|
|
pg_hba.conf | 17
|
|
pg_stat_tmp | 18
|
|
pg_subtrans | 19
|
|
(19 rows)
|
|
</programlisting>
|
|
</para>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="functions-info">
|
|
<title>System Information Functions and Operators</title>
|
|
|
|
<para>
|
|
The functions described in this section are used to obtain various
|
|
information about a <productname>PostgreSQL</productname> installation.
|
|
</para>
|
|
|
|
<sect2 id="functions-info-session">
|
|
<title>Session Information Functions</title>
|
|
|
|
<para>
|
|
<xref linkend="functions-info-session-table"/> shows several
|
|
functions that extract session and system information.
|
|
</para>
|
|
|
|
<para>
|
|
In addition to the functions listed in this section, there are a number of
|
|
functions related to the statistics system that also provide system
|
|
information. See <xref linkend="monitoring-stats-functions"/> for more
|
|
information.
|
|
</para>
|
|
|
|
<table id="functions-info-session-table">
|
|
<title>Session Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_catalog</primary>
|
|
</indexterm>
|
|
<function>current_catalog</function>
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_database</primary>
|
|
</indexterm>
|
|
<function>current_database</function> ()
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the name of the current database. (Databases are
|
|
called <quote>catalogs</quote> in the SQL standard,
|
|
so <function>current_catalog</function> is the standard's
|
|
spelling.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_query</primary>
|
|
</indexterm>
|
|
<function>current_query</function> ()
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the text of the currently executing query, as submitted
|
|
by the client (which might contain more than one statement).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_role</primary>
|
|
</indexterm>
|
|
<function>current_role</function>
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para>
|
|
This is equivalent to <function>current_user</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_schema</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>schema</primary>
|
|
<secondary>current</secondary>
|
|
</indexterm>
|
|
<function>current_schema</function>
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>current_schema</function> ()
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the name of the schema that is first in the search path (or a
|
|
null value if the search path is empty). This is the schema that will
|
|
be used for any tables or other named objects that are created without
|
|
specifying a target schema.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_schemas</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>search path</primary>
|
|
<secondary>current</secondary>
|
|
</indexterm>
|
|
<function>current_schemas</function> ( <parameter>include_implicit</parameter> <type>boolean</type> )
|
|
<returnvalue>name[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an array of the names of all schemas presently in the
|
|
effective search path, in their priority order. (Items in the current
|
|
<xref linkend="guc-search-path"/> setting that do not correspond to
|
|
existing, searchable schemas are omitted.) If the Boolean argument
|
|
is <literal>true</literal>, then implicitly-searched system schemas
|
|
such as <literal>pg_catalog</literal> are included in the result.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_user</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>user</primary>
|
|
<secondary>current</secondary>
|
|
</indexterm>
|
|
<function>current_user</function>
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the user name of the current execution context.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>inet_client_addr</primary>
|
|
</indexterm>
|
|
<function>inet_client_addr</function> ()
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the IP address of the current client,
|
|
or <literal>NULL</literal> if the current connection is via a
|
|
Unix-domain socket.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>inet_client_port</primary>
|
|
</indexterm>
|
|
<function>inet_client_port</function> ()
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the IP port number of the current client,
|
|
or <literal>NULL</literal> if the current connection is via a
|
|
Unix-domain socket.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>inet_server_addr</primary>
|
|
</indexterm>
|
|
<function>inet_server_addr</function> ()
|
|
<returnvalue>inet</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the IP address on which the server accepted the current
|
|
connection,
|
|
or <literal>NULL</literal> if the current connection is via a
|
|
Unix-domain socket.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>inet_server_port</primary>
|
|
</indexterm>
|
|
<function>inet_server_port</function> ()
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the IP port number on which the server accepted the current
|
|
connection,
|
|
or <literal>NULL</literal> if the current connection is via a
|
|
Unix-domain socket.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_backend_pid</primary>
|
|
</indexterm>
|
|
<function>pg_backend_pid</function> ()
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the process ID of the server process attached to the current
|
|
session.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_blocking_pids</primary>
|
|
</indexterm>
|
|
<function>pg_blocking_pids</function> ( <type>integer</type> )
|
|
<returnvalue>integer[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an array of the process ID(s) of the sessions that are
|
|
blocking the server process with the specified process ID from
|
|
acquiring a lock, or an empty array if there is no such server process
|
|
or it is not blocked.
|
|
</para>
|
|
<para>
|
|
One server process blocks another if it either holds a lock that
|
|
conflicts with the blocked process's lock request (hard block), or is
|
|
waiting for a lock that would conflict with the blocked process's lock
|
|
request and is ahead of it in the wait queue (soft block). When using
|
|
parallel queries the result always lists client-visible process IDs
|
|
(that is, <function>pg_backend_pid</function> results) even if the
|
|
actual lock is held or awaited by a child worker process. As a result
|
|
of that, there may be duplicated PIDs in the result. Also note that
|
|
when a prepared transaction holds a conflicting lock, it will be
|
|
represented by a zero process ID.
|
|
</para>
|
|
<para>
|
|
Frequent calls to this function could have some impact on database
|
|
performance, because it needs exclusive access to the lock manager's
|
|
shared state for a short time.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_conf_load_time</primary>
|
|
</indexterm>
|
|
<function>pg_conf_load_time</function> ()
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the time when the server configuration files were last loaded.
|
|
If the current session was alive at the time, this will be the time
|
|
when the session itself re-read the configuration files (so the
|
|
reading will vary a little in different sessions). Otherwise it is
|
|
the time when the postmaster process re-read the configuration files.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_current_logfile</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>Logging</primary>
|
|
<secondary>pg_current_logfile function</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>current_logfiles</primary>
|
|
<secondary>and the pg_current_logfile function</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>Logging</primary>
|
|
<secondary>current_logfiles file and the pg_current_logfile
|
|
function</secondary>
|
|
</indexterm>
|
|
<function>pg_current_logfile</function> ( <optional> <type>text</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the path name of the log file currently in use by the logging
|
|
collector. The path includes the <xref linkend="guc-log-directory"/>
|
|
directory and the individual log file name. The result
|
|
is <literal>NULL</literal> if the logging collector is disabled.
|
|
When multiple log files exist, each in a different
|
|
format, <function>pg_current_logfile</function> without an argument
|
|
returns the path of the file having the first format found in the
|
|
ordered list: <literal>stderr</literal>,
|
|
<literal>csvlog</literal>, <literal>jsonlog</literal>.
|
|
<literal>NULL</literal> is returned if no log file has any of these
|
|
formats.
|
|
To request information about a specific log file format, supply
|
|
either <literal>csvlog</literal>, <literal>jsonlog</literal> or
|
|
<literal>stderr</literal> as the
|
|
value of the optional parameter. The result is <literal>NULL</literal>
|
|
if the log format requested is not configured in
|
|
<xref linkend="guc-log-destination"/>.
|
|
The result reflects the contents of
|
|
the <filename>current_logfiles</filename> file.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers and roles with privileges of
|
|
the <literal>pg_monitor</literal> role by default, but other users can
|
|
be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_my_temp_schema</primary>
|
|
</indexterm>
|
|
<function>pg_my_temp_schema</function> ()
|
|
<returnvalue>oid</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the OID of the current session's temporary schema, or zero if
|
|
it has none (because it has not created any temporary tables).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_is_other_temp_schema</primary>
|
|
</indexterm>
|
|
<function>pg_is_other_temp_schema</function> ( <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns true if the given OID is the OID of another session's
|
|
temporary schema. (This can be useful, for example, to exclude other
|
|
sessions' temporary tables from a catalog display.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_jit_available</primary>
|
|
</indexterm>
|
|
<function>pg_jit_available</function> ()
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns true if a <acronym>JIT</acronym> compiler extension is
|
|
available (see <xref linkend="jit"/>) and the
|
|
<xref linkend="guc-jit"/> configuration parameter is set to
|
|
<literal>on</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_listening_channels</primary>
|
|
</indexterm>
|
|
<function>pg_listening_channels</function> ()
|
|
<returnvalue>setof text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the set of names of asynchronous notification channels that
|
|
the current session is listening to.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_notification_queue_usage</primary>
|
|
</indexterm>
|
|
<function>pg_notification_queue_usage</function> ()
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the fraction (0–1) of the asynchronous notification
|
|
queue's maximum size that is currently occupied by notifications that
|
|
are waiting to be processed.
|
|
See <xref linkend="sql-listen"/> and <xref linkend="sql-notify"/>
|
|
for more information.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_postmaster_start_time</primary>
|
|
</indexterm>
|
|
<function>pg_postmaster_start_time</function> ()
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the time when the server started.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_safe_snapshot_blocking_pids</primary>
|
|
</indexterm>
|
|
<function>pg_safe_snapshot_blocking_pids</function> ( <type>integer</type> )
|
|
<returnvalue>integer[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an array of the process ID(s) of the sessions that are blocking
|
|
the server process with the specified process ID from acquiring a safe
|
|
snapshot, or an empty array if there is no such server process or it
|
|
is not blocked.
|
|
</para>
|
|
<para>
|
|
A session running a <literal>SERIALIZABLE</literal> transaction blocks
|
|
a <literal>SERIALIZABLE READ ONLY DEFERRABLE</literal> transaction
|
|
from acquiring a snapshot until the latter determines that it is safe
|
|
to avoid taking any predicate locks. See
|
|
<xref linkend="xact-serializable"/> for more information about
|
|
serializable and deferrable transactions.
|
|
</para>
|
|
<para>
|
|
Frequent calls to this function could have some impact on database
|
|
performance, because it needs access to the predicate lock manager's
|
|
shared state for a short time.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_trigger_depth</primary>
|
|
</indexterm>
|
|
<function>pg_trigger_depth</function> ()
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the current nesting level
|
|
of <productname>PostgreSQL</productname> triggers (0 if not called,
|
|
directly or indirectly, from inside a trigger).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>session_user</primary>
|
|
</indexterm>
|
|
<function>session_user</function>
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the session user's name.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>system_user</primary>
|
|
</indexterm>
|
|
<function>system_user</function>
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the authentication method and the identity (if any) that the
|
|
user presented during the authentication cycle before they were
|
|
assigned a database role. It is represented as
|
|
<literal>auth_method:identity</literal> or
|
|
<literal>NULL</literal> if the user has not been authenticated (for
|
|
example if <link linkend="auth-trust">Trust authentication</link> has
|
|
been used).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>user</primary>
|
|
</indexterm>
|
|
<function>user</function>
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para>
|
|
This is equivalent to <function>current_user</function>.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>
|
|
<function>current_catalog</function>,
|
|
<function>current_role</function>,
|
|
<function>current_schema</function>,
|
|
<function>current_user</function>,
|
|
<function>session_user</function>,
|
|
and <function>user</function> have special syntactic status
|
|
in <acronym>SQL</acronym>: they must be called without trailing
|
|
parentheses. In PostgreSQL, parentheses can optionally be used with
|
|
<function>current_schema</function>, but not with the others.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
The <function>session_user</function> is normally the user who initiated
|
|
the current database connection; but superusers can change this setting
|
|
with <xref linkend="sql-set-session-authorization"/>.
|
|
The <function>current_user</function> is the user identifier
|
|
that is applicable for permission checking. Normally it is equal
|
|
to the session user, but it can be changed with
|
|
<xref linkend="sql-set-role"/>.
|
|
It also changes during the execution of
|
|
functions with the attribute <literal>SECURITY DEFINER</literal>.
|
|
In Unix parlance, the session user is the <quote>real user</quote> and
|
|
the current user is the <quote>effective user</quote>.
|
|
<function>current_role</function> and <function>user</function> are
|
|
synonyms for <function>current_user</function>. (The SQL standard draws
|
|
a distinction between <function>current_role</function>
|
|
and <function>current_user</function>, but <productname>PostgreSQL</productname>
|
|
does not, since it unifies users and roles into a single kind of entity.)
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-access">
|
|
<title>Access Privilege Inquiry Functions</title>
|
|
|
|
<indexterm>
|
|
<primary>privilege</primary>
|
|
<secondary>querying</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<xref linkend="functions-info-access-table"/> lists functions that
|
|
allow querying object access privileges programmatically.
|
|
(See <xref linkend="ddl-priv"/> for more information about
|
|
privileges.)
|
|
In these functions, the user whose privileges are being inquired about
|
|
can be specified by name or by OID
|
|
(<structname>pg_authid</structname>.<structfield>oid</structfield>), or if
|
|
the name is given as <literal>public</literal> then the privileges of the
|
|
PUBLIC pseudo-role are checked. Also, the <parameter>user</parameter>
|
|
argument can be omitted entirely, in which case
|
|
the <function>current_user</function> is assumed.
|
|
The object that is being inquired about can be specified either by name or
|
|
by OID, too. When specifying by name, a schema name can be included if
|
|
relevant.
|
|
The access privilege of interest is specified by a text string, which must
|
|
evaluate to one of the appropriate privilege keywords for the object's type
|
|
(e.g., <literal>SELECT</literal>). Optionally, <literal>WITH GRANT
|
|
OPTION</literal> can be added to a privilege type to test whether the
|
|
privilege is held with grant option. Also, multiple privilege types can be
|
|
listed separated by commas, in which case the result will be true if any of
|
|
the listed privileges is held. (Case of the privilege string is not
|
|
significant, and extra whitespace is allowed between but not within
|
|
privilege names.)
|
|
Some examples:
|
|
<programlisting>
|
|
SELECT has_table_privilege('myschema.mytable', 'select');
|
|
SELECT has_table_privilege('joe', 'mytable', 'INSERT, SELECT WITH GRANT OPTION');
|
|
</programlisting>
|
|
</para>
|
|
|
|
<table id="functions-info-access-table">
|
|
<title>Access Privilege Inquiry Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_any_column_privilege</primary>
|
|
</indexterm>
|
|
<function>has_any_column_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>table</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for any column of table?
|
|
This succeeds either if the privilege is held for the whole table, or
|
|
if there is a column-level grant of the privilege for at least one
|
|
column.
|
|
Allowable privilege types are
|
|
<literal>SELECT</literal>, <literal>INSERT</literal>,
|
|
<literal>UPDATE</literal>, and <literal>REFERENCES</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_column_privilege</primary>
|
|
</indexterm>
|
|
<function>has_column_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>table</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>column</parameter> <type>text</type> or <type>smallint</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for the specified table column?
|
|
This succeeds either if the privilege is held for the whole table, or
|
|
if there is a column-level grant of the privilege for the column.
|
|
The column can be specified by name or by attribute number
|
|
(<structname>pg_attribute</structname>.<structfield>attnum</structfield>).
|
|
Allowable privilege types are
|
|
<literal>SELECT</literal>, <literal>INSERT</literal>,
|
|
<literal>UPDATE</literal>, and <literal>REFERENCES</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_database_privilege</primary>
|
|
</indexterm>
|
|
<function>has_database_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>database</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for database?
|
|
Allowable privilege types are
|
|
<literal>CREATE</literal>,
|
|
<literal>CONNECT</literal>,
|
|
<literal>TEMPORARY</literal>, and
|
|
<literal>TEMP</literal> (which is equivalent to
|
|
<literal>TEMPORARY</literal>).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_foreign_data_wrapper_privilege</primary>
|
|
</indexterm>
|
|
<function>has_foreign_data_wrapper_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>fdw</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for foreign-data wrapper?
|
|
The only allowable privilege type is <literal>USAGE</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_function_privilege</primary>
|
|
</indexterm>
|
|
<function>has_function_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>function</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for function?
|
|
The only allowable privilege type is <literal>EXECUTE</literal>.
|
|
</para>
|
|
<para>
|
|
When specifying a function by name rather than by OID, the allowed
|
|
input is the same as for the <type>regprocedure</type> data type (see
|
|
<xref linkend="datatype-oid"/>).
|
|
An example is:
|
|
<programlisting>
|
|
SELECT has_function_privilege('joeuser', 'myfunc(int, text)', 'execute');
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_language_privilege</primary>
|
|
</indexterm>
|
|
<function>has_language_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>language</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for language?
|
|
The only allowable privilege type is <literal>USAGE</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_parameter_privilege</primary>
|
|
</indexterm>
|
|
<function>has_parameter_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>parameter</parameter> <type>text</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for configuration parameter?
|
|
The parameter name is case-insensitive.
|
|
Allowable privilege types are <literal>SET</literal>
|
|
and <literal>ALTER SYSTEM</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_schema_privilege</primary>
|
|
</indexterm>
|
|
<function>has_schema_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>schema</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for schema?
|
|
Allowable privilege types are
|
|
<literal>CREATE</literal> and
|
|
<literal>USAGE</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_sequence_privilege</primary>
|
|
</indexterm>
|
|
<function>has_sequence_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>sequence</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for sequence?
|
|
Allowable privilege types are
|
|
<literal>USAGE</literal>,
|
|
<literal>SELECT</literal>, and
|
|
<literal>UPDATE</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_server_privilege</primary>
|
|
</indexterm>
|
|
<function>has_server_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>server</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for foreign server?
|
|
The only allowable privilege type is <literal>USAGE</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_table_privilege</primary>
|
|
</indexterm>
|
|
<function>has_table_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>table</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for table?
|
|
Allowable privilege types
|
|
are <literal>SELECT</literal>, <literal>INSERT</literal>,
|
|
<literal>UPDATE</literal>, <literal>DELETE</literal>,
|
|
<literal>TRUNCATE</literal>, <literal>REFERENCES</literal>,
|
|
<literal>TRIGGER</literal>, and <literal>MAINTAIN</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_tablespace_privilege</primary>
|
|
</indexterm>
|
|
<function>has_tablespace_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>tablespace</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for tablespace?
|
|
The only allowable privilege type is <literal>CREATE</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>has_type_privilege</primary>
|
|
</indexterm>
|
|
<function>has_type_privilege</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>type</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for data type?
|
|
The only allowable privilege type is <literal>USAGE</literal>.
|
|
When specifying a type by name rather than by OID, the allowed input
|
|
is the same as for the <type>regtype</type> data type (see
|
|
<xref linkend="datatype-oid"/>).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_has_role</primary>
|
|
</indexterm>
|
|
<function>pg_has_role</function> (
|
|
<optional> <parameter>user</parameter> <type>name</type> or <type>oid</type>, </optional>
|
|
<parameter>role</parameter> <type>text</type> or <type>oid</type>,
|
|
<parameter>privilege</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does user have privilege for role?
|
|
Allowable privilege types are
|
|
<literal>MEMBER</literal>, <literal>USAGE</literal>,
|
|
and <literal>SET</literal>.
|
|
<literal>MEMBER</literal> denotes direct or indirect membership in
|
|
the role without regard to what specific privileges may be conferred.
|
|
<literal>USAGE</literal> denotes whether the privileges of the role
|
|
are immediately available without doing <command>SET ROLE</command>,
|
|
while <literal>SET</literal> denotes whether it is possible to change
|
|
to the role using the <literal>SET ROLE</literal> command.
|
|
This function does not allow the special case of
|
|
setting <parameter>user</parameter> to <literal>public</literal>,
|
|
because the PUBLIC pseudo-role can never be a member of real roles.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>row_security_active</primary>
|
|
</indexterm>
|
|
<function>row_security_active</function> (
|
|
<parameter>table</parameter> <type>text</type> or <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is row-level security active for the specified table in the context of
|
|
the current user and current environment?
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-aclitem-op-table"/> shows the operators
|
|
available for the <type>aclitem</type> type, which is the catalog
|
|
representation of access privileges. See <xref linkend="ddl-priv"/>
|
|
for information about how to read access privilege values.
|
|
</para>
|
|
|
|
<table id="functions-aclitem-op-table">
|
|
<title><type>aclitem</type> Operators</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Operator
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>aclitemeq</primary>
|
|
</indexterm>
|
|
<type>aclitem</type> <literal>=</literal> <type>aclitem</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Are <type>aclitem</type>s equal? (Notice that
|
|
type <type>aclitem</type> lacks the usual set of comparison
|
|
operators; it has only equality. In turn, <type>aclitem</type>
|
|
arrays can only be compared for equality.)
|
|
</para>
|
|
<para>
|
|
<literal>'calvin=r*w/hobbes'::aclitem = 'calvin=r*w*/hobbes'::aclitem</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>aclcontains</primary>
|
|
</indexterm>
|
|
<type>aclitem[]</type> <literal>@></literal> <type>aclitem</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Does array contain the specified privileges? (This is true if there
|
|
is an array entry that matches the <type>aclitem</type>'s grantee and
|
|
grantor, and has at least the specified set of privileges.)
|
|
</para>
|
|
<para>
|
|
<literal>'{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] @> 'calvin=r*/hobbes'::aclitem</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<type>aclitem[]</type> <literal>~</literal> <type>aclitem</type>
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
This is a deprecated alias for <literal>@></literal>.
|
|
</para>
|
|
<para>
|
|
<literal>'{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] ~ 'calvin=r*/hobbes'::aclitem</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-aclitem-fn-table"/> shows some additional
|
|
functions to manage the <type>aclitem</type> type.
|
|
</para>
|
|
|
|
<table id="functions-aclitem-fn-table">
|
|
<title><type>aclitem</type> Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>acldefault</primary>
|
|
</indexterm>
|
|
<function>acldefault</function> (
|
|
<parameter>type</parameter> <type>"char"</type>,
|
|
<parameter>ownerId</parameter> <type>oid</type> )
|
|
<returnvalue>aclitem[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Constructs an <type>aclitem</type> array holding the default access
|
|
privileges for an object of type <parameter>type</parameter> belonging
|
|
to the role with OID <parameter>ownerId</parameter>. This represents
|
|
the access privileges that will be assumed when an object's ACL entry
|
|
is null. (The default access privileges are described in
|
|
<xref linkend="ddl-priv"/>.)
|
|
The <parameter>type</parameter> parameter must be one of
|
|
'c' for <literal>COLUMN</literal>,
|
|
'r' for <literal>TABLE</literal> and table-like objects,
|
|
's' for <literal>SEQUENCE</literal>,
|
|
'd' for <literal>DATABASE</literal>,
|
|
'f' for <literal>FUNCTION</literal> or <literal>PROCEDURE</literal>,
|
|
'l' for <literal>LANGUAGE</literal>,
|
|
'L' for <literal>LARGE OBJECT</literal>,
|
|
'n' for <literal>SCHEMA</literal>,
|
|
'p' for <literal>PARAMETER</literal>,
|
|
't' for <literal>TABLESPACE</literal>,
|
|
'F' for <literal>FOREIGN DATA WRAPPER</literal>,
|
|
'S' for <literal>FOREIGN SERVER</literal>,
|
|
or
|
|
'T' for <literal>TYPE</literal> or <literal>DOMAIN</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>aclexplode</primary>
|
|
</indexterm>
|
|
<function>aclexplode</function> ( <type>aclitem[]</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>grantor</parameter> <type>oid</type>,
|
|
<parameter>grantee</parameter> <type>oid</type>,
|
|
<parameter>privilege_type</parameter> <type>text</type>,
|
|
<parameter>is_grantable</parameter> <type>boolean</type> )
|
|
</para>
|
|
<para>
|
|
Returns the <type>aclitem</type> array as a set of rows.
|
|
If the grantee is the pseudo-role PUBLIC, it is represented by zero in
|
|
the <parameter>grantee</parameter> column. Each granted privilege is
|
|
represented as <literal>SELECT</literal>, <literal>INSERT</literal>,
|
|
etc (see <xref linkend="privilege-abbrevs-table"/> for a full list).
|
|
Note that each privilege is broken out as a separate row, so
|
|
only one keyword appears in the <parameter>privilege_type</parameter>
|
|
column.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>makeaclitem</primary>
|
|
</indexterm>
|
|
<function>makeaclitem</function> (
|
|
<parameter>grantee</parameter> <type>oid</type>,
|
|
<parameter>grantor</parameter> <type>oid</type>,
|
|
<parameter>privileges</parameter> <type>text</type>,
|
|
<parameter>is_grantable</parameter> <type>boolean</type> )
|
|
<returnvalue>aclitem</returnvalue>
|
|
</para>
|
|
<para>
|
|
Constructs an <type>aclitem</type> with the given properties.
|
|
<parameter>privileges</parameter> is a comma-separated list of
|
|
privilege names such as <literal>SELECT</literal>,
|
|
<literal>INSERT</literal>, etc, all of which are set in the
|
|
result. (Case of the privilege string is not significant, and
|
|
extra whitespace is allowed between but not within privilege
|
|
names.)
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-schema">
|
|
<title>Schema Visibility Inquiry Functions</title>
|
|
|
|
<para>
|
|
<xref linkend="functions-info-schema-table"/> shows functions that
|
|
determine whether a certain object is <firstterm>visible</firstterm> in the
|
|
current schema search path.
|
|
For example, a table is said to be visible if its
|
|
containing schema is in the search path and no table of the same
|
|
name appears earlier in the search path. This is equivalent to the
|
|
statement that the table can be referenced by name without explicit
|
|
schema qualification. Thus, to list the names of all visible tables:
|
|
<programlisting>
|
|
SELECT relname FROM pg_class WHERE pg_table_is_visible(oid);
|
|
</programlisting>
|
|
For functions and operators, an object in the search path is said to be
|
|
visible if there is no object of the same name <emphasis>and argument data
|
|
type(s)</emphasis> earlier in the path. For operator classes and families,
|
|
both the name and the associated index access method are considered.
|
|
</para>
|
|
|
|
<indexterm>
|
|
<primary>search path</primary>
|
|
<secondary>object visibility</secondary>
|
|
</indexterm>
|
|
|
|
<table id="functions-info-schema-table">
|
|
<title>Schema Visibility Inquiry Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_collation_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_collation_is_visible</function> ( <parameter>collation</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is collation visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_conversion_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_conversion_is_visible</function> ( <parameter>conversion</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is conversion visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_function_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_function_is_visible</function> ( <parameter>function</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is function visible in search path?
|
|
(This also works for procedures and aggregates.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_opclass_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_opclass_is_visible</function> ( <parameter>opclass</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is operator class visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_operator_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_operator_is_visible</function> ( <parameter>operator</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is operator visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_opfamily_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_opfamily_is_visible</function> ( <parameter>opclass</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is operator family visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_statistics_obj_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_statistics_obj_is_visible</function> ( <parameter>stat</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is statistics object visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_table_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_table_is_visible</function> ( <parameter>table</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is table visible in search path?
|
|
(This works for all types of relations, including views, materialized
|
|
views, indexes, sequences and foreign tables.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ts_config_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_ts_config_is_visible</function> ( <parameter>config</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is text search configuration visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ts_dict_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_ts_dict_is_visible</function> ( <parameter>dict</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is text search dictionary visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ts_parser_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_ts_parser_is_visible</function> ( <parameter>parser</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is text search parser visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ts_template_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_ts_template_is_visible</function> ( <parameter>template</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is text search template visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_type_is_visible</primary>
|
|
</indexterm>
|
|
<function>pg_type_is_visible</function> ( <parameter>type</parameter> <type>oid</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is type (or domain) visible in search path?
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
All these functions require object OIDs to identify the object to be
|
|
checked. If you want to test an object by name, it is convenient to use
|
|
the OID alias types (<type>regclass</type>, <type>regtype</type>,
|
|
<type>regprocedure</type>, <type>regoperator</type>, <type>regconfig</type>,
|
|
or <type>regdictionary</type>),
|
|
for example:
|
|
<programlisting>
|
|
SELECT pg_type_is_visible('myschema.widget'::regtype);
|
|
</programlisting>
|
|
Note that it would not make much sense to test a non-schema-qualified
|
|
type name in this way — if the name can be recognized at all, it must be visible.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-catalog">
|
|
<title>System Catalog Information Functions</title>
|
|
|
|
<para>
|
|
<xref linkend="functions-info-catalog-table"/> lists functions that
|
|
extract information from the system catalogs.
|
|
</para>
|
|
|
|
<table id="functions-info-catalog-table">
|
|
<title>System Catalog Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry id="format-type" xreflabel="format_type" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>format_type</primary>
|
|
</indexterm>
|
|
<function>format_type</function> ( <parameter>type</parameter> <type>oid</type>, <parameter>typemod</parameter> <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the SQL name for a data type that is identified by its type
|
|
OID and possibly a type modifier. Pass NULL for the type modifier if
|
|
no specific modifier is known.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_basetype</primary>
|
|
</indexterm>
|
|
<function>pg_basetype</function> ( <type>regtype</type> )
|
|
<returnvalue>regtype</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the OID of the base type of a domain identified by its
|
|
type OID. If the argument is the OID of a non-domain type,
|
|
returns the argument as-is. Returns NULL if the argument is
|
|
not a valid type OID. If there's a chain of domain dependencies,
|
|
it will recurse until finding the base type.
|
|
</para>
|
|
<para>
|
|
Assuming <literal>CREATE DOMAIN mytext AS text</literal>:
|
|
</para>
|
|
<para>
|
|
<literal>pg_basetype('mytext'::regtype)</literal>
|
|
<returnvalue>text</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-char-to-encoding" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_char_to_encoding</primary>
|
|
</indexterm>
|
|
<function>pg_char_to_encoding</function> ( <parameter>encoding</parameter> <type>name</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the supplied encoding name into an integer representing the
|
|
internal identifier used in some system catalog tables.
|
|
Returns <literal>-1</literal> if an unknown encoding name is provided.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-encoding-to-char" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_encoding_to_char</primary>
|
|
</indexterm>
|
|
<function>pg_encoding_to_char</function> ( <parameter>encoding</parameter> <type>integer</type> )
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts the integer used as the internal identifier of an encoding in some
|
|
system catalog tables into a human-readable string.
|
|
Returns an empty string if an invalid encoding number is provided.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_catalog_foreign_keys</primary>
|
|
</indexterm>
|
|
<function>pg_get_catalog_foreign_keys</function> ()
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>fktable</parameter> <type>regclass</type>,
|
|
<parameter>fkcols</parameter> <type>text[]</type>,
|
|
<parameter>pktable</parameter> <type>regclass</type>,
|
|
<parameter>pkcols</parameter> <type>text[]</type>,
|
|
<parameter>is_array</parameter> <type>boolean</type>,
|
|
<parameter>is_opt</parameter> <type>boolean</type> )
|
|
</para>
|
|
<para>
|
|
Returns a set of records describing the foreign key relationships
|
|
that exist within the <productname>PostgreSQL</productname> system
|
|
catalogs.
|
|
The <parameter>fktable</parameter> column contains the name of the
|
|
referencing catalog, and the <parameter>fkcols</parameter> column
|
|
contains the name(s) of the referencing column(s). Similarly,
|
|
the <parameter>pktable</parameter> column contains the name of the
|
|
referenced catalog, and the <parameter>pkcols</parameter> column
|
|
contains the name(s) of the referenced column(s).
|
|
If <parameter>is_array</parameter> is true, the last referencing
|
|
column is an array, each of whose elements should match some entry
|
|
in the referenced catalog.
|
|
If <parameter>is_opt</parameter> is true, the referencing column(s)
|
|
are allowed to contain zeroes instead of a valid reference.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_constraintdef</primary>
|
|
</indexterm>
|
|
<function>pg_get_constraintdef</function> ( <parameter>constraint</parameter> <type>oid</type> <optional>, <parameter>pretty</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the creating command for a constraint.
|
|
(This is a decompiled reconstruction, not the original text
|
|
of the command.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_expr</primary>
|
|
</indexterm>
|
|
<function>pg_get_expr</function> ( <parameter>expr</parameter> <type>pg_node_tree</type>, <parameter>relation</parameter> <type>oid</type> <optional>, <parameter>pretty</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Decompiles the internal form of an expression stored in the system
|
|
catalogs, such as the default value for a column. If the expression
|
|
might contain Vars, specify the OID of the relation they refer to as
|
|
the second parameter; if no Vars are expected, passing zero is
|
|
sufficient.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_functiondef</primary>
|
|
</indexterm>
|
|
<function>pg_get_functiondef</function> ( <parameter>func</parameter> <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the creating command for a function or procedure.
|
|
(This is a decompiled reconstruction, not the original text
|
|
of the command.)
|
|
The result is a complete <command>CREATE OR REPLACE FUNCTION</command>
|
|
or <command>CREATE OR REPLACE PROCEDURE</command> statement.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_function_arguments</primary>
|
|
</indexterm>
|
|
<function>pg_get_function_arguments</function> ( <parameter>func</parameter> <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the argument list of a function or procedure, in the form
|
|
it would need to appear in within <command>CREATE FUNCTION</command>
|
|
(including default values).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_function_identity_arguments</primary>
|
|
</indexterm>
|
|
<function>pg_get_function_identity_arguments</function> ( <parameter>func</parameter> <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the argument list necessary to identify a function or
|
|
procedure, in the form it would need to appear in within commands such
|
|
as <command>ALTER FUNCTION</command>. This form omits default values.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_function_result</primary>
|
|
</indexterm>
|
|
<function>pg_get_function_result</function> ( <parameter>func</parameter> <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the <literal>RETURNS</literal> clause of a function, in
|
|
the form it would need to appear in within <command>CREATE
|
|
FUNCTION</command>. Returns <literal>NULL</literal> for a procedure.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_indexdef</primary>
|
|
</indexterm>
|
|
<function>pg_get_indexdef</function> ( <parameter>index</parameter> <type>oid</type> <optional>, <parameter>column</parameter> <type>integer</type>, <parameter>pretty</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the creating command for an index.
|
|
(This is a decompiled reconstruction, not the original text
|
|
of the command.) If <parameter>column</parameter> is supplied and is
|
|
not zero, only the definition of that column is reconstructed.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_keywords</primary>
|
|
</indexterm>
|
|
<function>pg_get_keywords</function> ()
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>word</parameter> <type>text</type>,
|
|
<parameter>catcode</parameter> <type>"char"</type>,
|
|
<parameter>barelabel</parameter> <type>boolean</type>,
|
|
<parameter>catdesc</parameter> <type>text</type>,
|
|
<parameter>baredesc</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Returns a set of records describing the SQL keywords recognized by the
|
|
server. The <parameter>word</parameter> column contains the
|
|
keyword. The <parameter>catcode</parameter> column contains a
|
|
category code: <literal>U</literal> for an unreserved
|
|
keyword, <literal>C</literal> for a keyword that can be a column
|
|
name, <literal>T</literal> for a keyword that can be a type or
|
|
function name, or <literal>R</literal> for a fully reserved keyword.
|
|
The <parameter>barelabel</parameter> column
|
|
contains <literal>true</literal> if the keyword can be used as
|
|
a <quote>bare</quote> column label in <command>SELECT</command> lists,
|
|
or <literal>false</literal> if it can only be used
|
|
after <literal>AS</literal>.
|
|
The <parameter>catdesc</parameter> column contains a
|
|
possibly-localized string describing the keyword's category.
|
|
The <parameter>baredesc</parameter> column contains a
|
|
possibly-localized string describing the keyword's column label status.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_partkeydef</primary>
|
|
</indexterm>
|
|
<function>pg_get_partkeydef</function> ( <parameter>table</parameter> <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the definition of a partitioned table's partition
|
|
key, in the form it would have in the <literal>PARTITION
|
|
BY</literal> clause of <command>CREATE TABLE</command>.
|
|
(This is a decompiled reconstruction, not the original text
|
|
of the command.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_ruledef</primary>
|
|
</indexterm>
|
|
<function>pg_get_ruledef</function> ( <parameter>rule</parameter> <type>oid</type> <optional>, <parameter>pretty</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the creating command for a rule.
|
|
(This is a decompiled reconstruction, not the original text
|
|
of the command.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_serial_sequence</primary>
|
|
</indexterm>
|
|
<function>pg_get_serial_sequence</function> ( <parameter>table</parameter> <type>text</type>, <parameter>column</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the name of the sequence associated with a column,
|
|
or NULL if no sequence is associated with the column.
|
|
If the column is an identity column, the associated sequence is the
|
|
sequence internally created for that column.
|
|
For columns created using one of the serial types
|
|
(<type>serial</type>, <type>smallserial</type>, <type>bigserial</type>),
|
|
it is the sequence created for that serial column definition.
|
|
In the latter case, the association can be modified or removed
|
|
with <command>ALTER SEQUENCE OWNED BY</command>.
|
|
(This function probably should have been
|
|
called <function>pg_get_owned_sequence</function>; its current name
|
|
reflects the fact that it has historically been used with serial-type
|
|
columns.) The first parameter is a table name with optional
|
|
schema, and the second parameter is a column name. Because the first
|
|
parameter potentially contains both schema and table names, it is
|
|
parsed per usual SQL rules, meaning it is lower-cased by default.
|
|
The second parameter, being just a column name, is treated literally
|
|
and so has its case preserved. The result is suitably formatted
|
|
for passing to the sequence functions (see
|
|
<xref linkend="functions-sequence"/>).
|
|
</para>
|
|
<para>
|
|
A typical use is in reading the current value of the sequence for an
|
|
identity or serial column, for example:
|
|
<programlisting>
|
|
SELECT currval(pg_get_serial_sequence('sometable', 'id'));
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_statisticsobjdef</primary>
|
|
</indexterm>
|
|
<function>pg_get_statisticsobjdef</function> ( <parameter>statobj</parameter> <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the creating command for an extended statistics object.
|
|
(This is a decompiled reconstruction, not the original text
|
|
of the command.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_triggerdef</primary>
|
|
</indexterm>
|
|
<function>pg_get_triggerdef</function> ( <parameter>trigger</parameter> <type>oid</type> <optional>, <parameter>pretty</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the creating command for a trigger.
|
|
(This is a decompiled reconstruction, not the original text
|
|
of the command.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_userbyid</primary>
|
|
</indexterm>
|
|
<function>pg_get_userbyid</function> ( <parameter>role</parameter> <type>oid</type> )
|
|
<returnvalue>name</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a role's name given its OID.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_viewdef</primary>
|
|
</indexterm>
|
|
<function>pg_get_viewdef</function> ( <parameter>view</parameter> <type>oid</type> <optional>, <parameter>pretty</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the underlying <command>SELECT</command> command for a
|
|
view or materialized view. (This is a decompiled reconstruction, not
|
|
the original text of the command.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>pg_get_viewdef</function> ( <parameter>view</parameter> <type>oid</type>, <parameter>wrap_column</parameter> <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the underlying <command>SELECT</command> command for a
|
|
view or materialized view. (This is a decompiled reconstruction, not
|
|
the original text of the command.) In this form of the function,
|
|
pretty-printing is always enabled, and long lines are wrapped to try
|
|
to keep them shorter than the specified number of columns.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>pg_get_viewdef</function> ( <parameter>view</parameter> <type>text</type> <optional>, <parameter>pretty</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reconstructs the underlying <command>SELECT</command> command for a
|
|
view or materialized view, working from a textual name for the view
|
|
rather than its OID. (This is deprecated; use the OID variant
|
|
instead.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_index_column_has_property</primary>
|
|
</indexterm>
|
|
<function>pg_index_column_has_property</function> ( <parameter>index</parameter> <type>regclass</type>, <parameter>column</parameter> <type>integer</type>, <parameter>property</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tests whether an index column has the named property.
|
|
Common index column properties are listed in
|
|
<xref linkend="functions-info-index-column-props"/>.
|
|
(Note that extension access methods can define additional property
|
|
names for their indexes.)
|
|
<literal>NULL</literal> is returned if the property name is not known
|
|
or does not apply to the particular object, or if the OID or column
|
|
number does not identify a valid object.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_index_has_property</primary>
|
|
</indexterm>
|
|
<function>pg_index_has_property</function> ( <parameter>index</parameter> <type>regclass</type>, <parameter>property</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tests whether an index has the named property.
|
|
Common index properties are listed in
|
|
<xref linkend="functions-info-index-props"/>.
|
|
(Note that extension access methods can define additional property
|
|
names for their indexes.)
|
|
<literal>NULL</literal> is returned if the property name is not known
|
|
or does not apply to the particular object, or if the OID does not
|
|
identify a valid object.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_indexam_has_property</primary>
|
|
</indexterm>
|
|
<function>pg_indexam_has_property</function> ( <parameter>am</parameter> <type>oid</type>, <parameter>property</parameter> <type>text</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tests whether an index access method has the named property.
|
|
Access method properties are listed in
|
|
<xref linkend="functions-info-indexam-props"/>.
|
|
<literal>NULL</literal> is returned if the property name is not known
|
|
or does not apply to the particular object, or if the OID does not
|
|
identify a valid object.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_options_to_table</primary>
|
|
</indexterm>
|
|
<function>pg_options_to_table</function> ( <parameter>options_array</parameter> <type>text[]</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>option_name</parameter> <type>text</type>,
|
|
<parameter>option_value</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Returns the set of storage options represented by a value from
|
|
<structname>pg_class</structname>.<structfield>reloptions</structfield> or
|
|
<structname>pg_attribute</structname>.<structfield>attoptions</structfield>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_settings_get_flags</primary>
|
|
</indexterm>
|
|
<function>pg_settings_get_flags</function> ( <parameter>guc</parameter> <type>text</type> )
|
|
<returnvalue>text[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns an array of the flags associated with the given GUC, or
|
|
<literal>NULL</literal> if it does not exist. The result is
|
|
an empty array if the GUC exists but there are no flags to show.
|
|
Only the most useful flags listed in
|
|
<xref linkend="functions-pg-settings-flags"/> are exposed.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_tablespace_databases</primary>
|
|
</indexterm>
|
|
<function>pg_tablespace_databases</function> ( <parameter>tablespace</parameter> <type>oid</type> )
|
|
<returnvalue>setof oid</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the set of OIDs of databases that have objects stored in the
|
|
specified tablespace. If this function returns any rows, the
|
|
tablespace is not empty and cannot be dropped. To identify the specific
|
|
objects populating the tablespace, you will need to connect to the
|
|
database(s) identified by <function>pg_tablespace_databases</function>
|
|
and query their <structname>pg_class</structname> catalogs.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_tablespace_location</primary>
|
|
</indexterm>
|
|
<function>pg_tablespace_location</function> ( <parameter>tablespace</parameter> <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the file system path that this tablespace is located in.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_typeof</primary>
|
|
</indexterm>
|
|
<function>pg_typeof</function> ( <type>"any"</type> )
|
|
<returnvalue>regtype</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the OID of the data type of the value that is passed to it.
|
|
This can be helpful for troubleshooting or dynamically constructing
|
|
SQL queries. The function is declared as
|
|
returning <type>regtype</type>, which is an OID alias type (see
|
|
<xref linkend="datatype-oid"/>); this means that it is the same as an
|
|
OID for comparison purposes but displays as a type name.
|
|
</para>
|
|
<para>
|
|
<literal>pg_typeof(33)</literal>
|
|
<returnvalue>integer</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>COLLATION FOR</primary>
|
|
</indexterm>
|
|
<function>COLLATION FOR</function> ( <type>"any"</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the name of the collation of the value that is passed to it.
|
|
The value is quoted and schema-qualified if necessary. If no
|
|
collation was derived for the argument expression,
|
|
then <literal>NULL</literal> is returned. If the argument is not of a
|
|
collatable data type, then an error is raised.
|
|
</para>
|
|
<para>
|
|
<literal>collation for ('foo'::text)</literal>
|
|
<returnvalue>"default"</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>collation for ('foo' COLLATE "de_DE")</literal>
|
|
<returnvalue>"de_DE"</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regclass</primary>
|
|
</indexterm>
|
|
<function>to_regclass</function> ( <type>text</type> )
|
|
<returnvalue>regclass</returnvalue>
|
|
</para>
|
|
<para>
|
|
Translates a textual relation name to its OID. A similar result is
|
|
obtained by casting the string to type <type>regclass</type> (see
|
|
<xref linkend="datatype-oid"/>); however, this function will return
|
|
<literal>NULL</literal> rather than throwing an error if the name is
|
|
not found.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regcollation</primary>
|
|
</indexterm>
|
|
<function>to_regcollation</function> ( <type>text</type> )
|
|
<returnvalue>regcollation</returnvalue>
|
|
</para>
|
|
<para>
|
|
Translates a textual collation name to its OID. A similar result is
|
|
obtained by casting the string to type <type>regcollation</type> (see
|
|
<xref linkend="datatype-oid"/>); however, this function will return
|
|
<literal>NULL</literal> rather than throwing an error if the name is
|
|
not found.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regnamespace</primary>
|
|
</indexterm>
|
|
<function>to_regnamespace</function> ( <type>text</type> )
|
|
<returnvalue>regnamespace</returnvalue>
|
|
</para>
|
|
<para>
|
|
Translates a textual schema name to its OID. A similar result is
|
|
obtained by casting the string to type <type>regnamespace</type> (see
|
|
<xref linkend="datatype-oid"/>); however, this function will return
|
|
<literal>NULL</literal> rather than throwing an error if the name is
|
|
not found.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regoper</primary>
|
|
</indexterm>
|
|
<function>to_regoper</function> ( <type>text</type> )
|
|
<returnvalue>regoper</returnvalue>
|
|
</para>
|
|
<para>
|
|
Translates a textual operator name to its OID. A similar result is
|
|
obtained by casting the string to type <type>regoper</type> (see
|
|
<xref linkend="datatype-oid"/>); however, this function will return
|
|
<literal>NULL</literal> rather than throwing an error if the name is
|
|
not found or is ambiguous.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regoperator</primary>
|
|
</indexterm>
|
|
<function>to_regoperator</function> ( <type>text</type> )
|
|
<returnvalue>regoperator</returnvalue>
|
|
</para>
|
|
<para>
|
|
Translates a textual operator name (with parameter types) to its OID. A similar result is
|
|
obtained by casting the string to type <type>regoperator</type> (see
|
|
<xref linkend="datatype-oid"/>); however, this function will return
|
|
<literal>NULL</literal> rather than throwing an error if the name is
|
|
not found.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regproc</primary>
|
|
</indexterm>
|
|
<function>to_regproc</function> ( <type>text</type> )
|
|
<returnvalue>regproc</returnvalue>
|
|
</para>
|
|
<para>
|
|
Translates a textual function or procedure name to its OID. A similar result is
|
|
obtained by casting the string to type <type>regproc</type> (see
|
|
<xref linkend="datatype-oid"/>); however, this function will return
|
|
<literal>NULL</literal> rather than throwing an error if the name is
|
|
not found or is ambiguous.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regprocedure</primary>
|
|
</indexterm>
|
|
<function>to_regprocedure</function> ( <type>text</type> )
|
|
<returnvalue>regprocedure</returnvalue>
|
|
</para>
|
|
<para>
|
|
Translates a textual function or procedure name (with argument types) to its OID. A similar result is
|
|
obtained by casting the string to type <type>regprocedure</type> (see
|
|
<xref linkend="datatype-oid"/>); however, this function will return
|
|
<literal>NULL</literal> rather than throwing an error if the name is
|
|
not found.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regrole</primary>
|
|
</indexterm>
|
|
<function>to_regrole</function> ( <type>text</type> )
|
|
<returnvalue>regrole</returnvalue>
|
|
</para>
|
|
<para>
|
|
Translates a textual role name to its OID. A similar result is
|
|
obtained by casting the string to type <type>regrole</type> (see
|
|
<xref linkend="datatype-oid"/>); however, this function will return
|
|
<literal>NULL</literal> rather than throwing an error if the name is
|
|
not found.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="to-regtype" xreflabel="to_regtype" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regtype</primary>
|
|
</indexterm>
|
|
<function>to_regtype</function> ( <type>text</type> )
|
|
<returnvalue>regtype</returnvalue>
|
|
</para>
|
|
<para>
|
|
Parses a string of text, extracts a potential type name from it,
|
|
and translates that name into a type OID. A syntax error in the
|
|
string will result in an error; but if the string is a
|
|
syntactically valid type name that happens not to be found in the
|
|
catalogs, the result is <literal>NULL</literal>. A similar result
|
|
is obtained by casting the string to type <type>regtype</type>
|
|
(see <xref linkend="datatype-oid"/>), except that that will throw
|
|
error for name not found.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>to_regtypemod</primary>
|
|
</indexterm>
|
|
<function>to_regtypemod</function> ( <type>text</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Parses a string of text, extracts a potential type name from it,
|
|
and translates its type modifier, if any. A syntax error in the
|
|
string will result in an error; but if the string is a
|
|
syntactically valid type name that happens not to be found in the
|
|
catalogs, the result is <literal>NULL</literal>. The result is
|
|
<literal>-1</literal> if no type modifier is present.
|
|
</para>
|
|
<para>
|
|
<function>to_regtypemod</function> can be combined with
|
|
<xref linkend="to-regtype"/> to produce appropriate inputs for
|
|
<xref linkend="format-type"/>, allowing a string representing a
|
|
type name to be canonicalized.
|
|
</para>
|
|
<para>
|
|
<literal>format_type(to_regtype('varchar(32)'), to_regtypemod('varchar(32)'))</literal>
|
|
<returnvalue>character varying(32)</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Most of the functions that reconstruct (decompile) database objects
|
|
have an optional <parameter>pretty</parameter> flag, which
|
|
if <literal>true</literal> causes the result to
|
|
be <quote>pretty-printed</quote>. Pretty-printing suppresses unnecessary
|
|
parentheses and adds whitespace for legibility.
|
|
The pretty-printed format is more readable, but the default format
|
|
is more likely to be interpreted the same way by future versions of
|
|
<productname>PostgreSQL</productname>; so avoid using pretty-printed output
|
|
for dump purposes. Passing <literal>false</literal> for
|
|
the <parameter>pretty</parameter> parameter yields the same result as
|
|
omitting the parameter.
|
|
</para>
|
|
|
|
<table id="functions-info-index-column-props">
|
|
<title>Index Column Properties</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row><entry>Name</entry><entry>Description</entry></row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>asc</literal></entry>
|
|
<entry>Does the column sort in ascending order on a forward scan?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>desc</literal></entry>
|
|
<entry>Does the column sort in descending order on a forward scan?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>nulls_first</literal></entry>
|
|
<entry>Does the column sort with nulls first on a forward scan?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>nulls_last</literal></entry>
|
|
<entry>Does the column sort with nulls last on a forward scan?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>orderable</literal></entry>
|
|
<entry>Does the column possess any defined sort ordering?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>distance_orderable</literal></entry>
|
|
<entry>Can the column be scanned in order by a <quote>distance</quote>
|
|
operator, for example <literal>ORDER BY col <-> constant</literal> ?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>returnable</literal></entry>
|
|
<entry>Can the column value be returned by an index-only scan?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>search_array</literal></entry>
|
|
<entry>Does the column natively support <literal>col = ANY(array)</literal>
|
|
searches?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>search_nulls</literal></entry>
|
|
<entry>Does the column support <literal>IS NULL</literal> and
|
|
<literal>IS NOT NULL</literal> searches?
|
|
</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-info-index-props">
|
|
<title>Index Properties</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row><entry>Name</entry><entry>Description</entry></row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>clusterable</literal></entry>
|
|
<entry>Can the index be used in a <literal>CLUSTER</literal> command?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>index_scan</literal></entry>
|
|
<entry>Does the index support plain (non-bitmap) scans?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>bitmap_scan</literal></entry>
|
|
<entry>Does the index support bitmap scans?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>backward_scan</literal></entry>
|
|
<entry>Can the scan direction be changed in mid-scan (to
|
|
support <literal>FETCH BACKWARD</literal> on a cursor without
|
|
needing materialization)?
|
|
</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-info-indexam-props">
|
|
<title>Index Access Method Properties</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row><entry>Name</entry><entry>Description</entry></row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>can_order</literal></entry>
|
|
<entry>Does the access method support <literal>ASC</literal>,
|
|
<literal>DESC</literal> and related keywords in
|
|
<literal>CREATE INDEX</literal>?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>can_unique</literal></entry>
|
|
<entry>Does the access method support unique indexes?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>can_multi_col</literal></entry>
|
|
<entry>Does the access method support indexes with multiple columns?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>can_exclude</literal></entry>
|
|
<entry>Does the access method support exclusion constraints?
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>can_include</literal></entry>
|
|
<entry>Does the access method support the <literal>INCLUDE</literal>
|
|
clause of <literal>CREATE INDEX</literal>?
|
|
</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-pg-settings-flags">
|
|
<title>GUC Flags</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row><entry>Flag</entry><entry>Description</entry></row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>EXPLAIN</literal></entry>
|
|
<entry>Parameters with this flag are included in
|
|
<command>EXPLAIN (SETTINGS)</command> commands.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>NO_SHOW_ALL</literal></entry>
|
|
<entry>Parameters with this flag are excluded from
|
|
<command>SHOW ALL</command> commands.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>NO_RESET</literal></entry>
|
|
<entry>Parameters with this flag do not support
|
|
<command>RESET</command> commands.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>NO_RESET_ALL</literal></entry>
|
|
<entry>Parameters with this flag are excluded from
|
|
<command>RESET ALL</command> commands.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>NOT_IN_SAMPLE</literal></entry>
|
|
<entry>Parameters with this flag are not included in
|
|
<filename>postgresql.conf</filename> by default.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>RUNTIME_COMPUTED</literal></entry>
|
|
<entry>Parameters with this flag are runtime-computed ones.
|
|
</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-object">
|
|
<title>Object Information and Addressing Functions</title>
|
|
|
|
<para>
|
|
<xref linkend="functions-info-object-table"/> lists functions related to
|
|
database object identification and addressing.
|
|
</para>
|
|
|
|
<table id="functions-info-object-table">
|
|
<title>Object Information and Addressing Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_describe_object</primary>
|
|
</indexterm>
|
|
<function>pg_describe_object</function> ( <parameter>classid</parameter> <type>oid</type>, <parameter>objid</parameter> <type>oid</type>, <parameter>objsubid</parameter> <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a textual description of a database object identified by
|
|
catalog OID, object OID, and sub-object ID (such as a column number
|
|
within a table; the sub-object ID is zero when referring to a whole
|
|
object). This description is intended to be human-readable, and might
|
|
be translated, depending on server configuration. This is especially
|
|
useful to determine the identity of an object referenced in the
|
|
<structname>pg_depend</structname> catalog. This function returns
|
|
<literal>NULL</literal> values for undefined objects.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_identify_object</primary>
|
|
</indexterm>
|
|
<function>pg_identify_object</function> ( <parameter>classid</parameter> <type>oid</type>, <parameter>objid</parameter> <type>oid</type>, <parameter>objsubid</parameter> <type>integer</type> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>type</parameter> <type>text</type>,
|
|
<parameter>schema</parameter> <type>text</type>,
|
|
<parameter>name</parameter> <type>text</type>,
|
|
<parameter>identity</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Returns a row containing enough information to uniquely identify the
|
|
database object specified by catalog OID, object OID and sub-object
|
|
ID.
|
|
This information is intended to be machine-readable, and is never
|
|
translated.
|
|
<parameter>type</parameter> identifies the type of database object;
|
|
<parameter>schema</parameter> is the schema name that the object
|
|
belongs in, or <literal>NULL</literal> for object types that do not
|
|
belong to schemas;
|
|
<parameter>name</parameter> is the name of the object, quoted if
|
|
necessary, if the name (along with schema name, if pertinent) is
|
|
sufficient to uniquely identify the object,
|
|
otherwise <literal>NULL</literal>;
|
|
<parameter>identity</parameter> is the complete object identity, with
|
|
the precise format depending on object type, and each name within the
|
|
format being schema-qualified and quoted as necessary. Undefined
|
|
objects are identified with <literal>NULL</literal> values.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_identify_object_as_address</primary>
|
|
</indexterm>
|
|
<function>pg_identify_object_as_address</function> ( <parameter>classid</parameter> <type>oid</type>, <parameter>objid</parameter> <type>oid</type>, <parameter>objsubid</parameter> <type>integer</type> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>type</parameter> <type>text</type>,
|
|
<parameter>object_names</parameter> <type>text[]</type>,
|
|
<parameter>object_args</parameter> <type>text[]</type> )
|
|
</para>
|
|
<para>
|
|
Returns a row containing enough information to uniquely identify the
|
|
database object specified by catalog OID, object OID and sub-object
|
|
ID.
|
|
The returned information is independent of the current server, that
|
|
is, it could be used to identify an identically named object in
|
|
another server.
|
|
<parameter>type</parameter> identifies the type of database object;
|
|
<parameter>object_names</parameter> and
|
|
<parameter>object_args</parameter>
|
|
are text arrays that together form a reference to the object.
|
|
These three values can be passed
|
|
to <function>pg_get_object_address</function> to obtain the internal
|
|
address of the object.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_object_address</primary>
|
|
</indexterm>
|
|
<function>pg_get_object_address</function> ( <parameter>type</parameter> <type>text</type>, <parameter>object_names</parameter> <type>text[]</type>, <parameter>object_args</parameter> <type>text[]</type> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>classid</parameter> <type>oid</type>,
|
|
<parameter>objid</parameter> <type>oid</type>,
|
|
<parameter>objsubid</parameter> <type>integer</type> )
|
|
</para>
|
|
<para>
|
|
Returns a row containing enough information to uniquely identify the
|
|
database object specified by a type code and object name and argument
|
|
arrays.
|
|
The returned values are the ones that would be used in system catalogs
|
|
such as <structname>pg_depend</structname>; they can be passed to
|
|
other system functions such as <function>pg_describe_object</function>
|
|
or <function>pg_identify_object</function>.
|
|
<parameter>classid</parameter> is the OID of the system catalog
|
|
containing the object;
|
|
<parameter>objid</parameter> is the OID of the object itself, and
|
|
<parameter>objsubid</parameter> is the sub-object ID, or zero if none.
|
|
This function is the inverse
|
|
of <function>pg_identify_object_as_address</function>.
|
|
Undefined objects are identified with <literal>NULL</literal> values.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-comment">
|
|
<title>Comment Information Functions</title>
|
|
|
|
<indexterm>
|
|
<primary>comment</primary>
|
|
<secondary sortas="database objects">about database objects</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-info-comment-table"/>
|
|
extract comments previously stored with the <xref linkend="sql-comment"/>
|
|
command. A null value is returned if no
|
|
comment could be found for the specified parameters.
|
|
</para>
|
|
|
|
<table id="functions-info-comment-table">
|
|
<title>Comment Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>col_description</primary>
|
|
</indexterm>
|
|
<function>col_description</function> ( <parameter>table</parameter> <type>oid</type>, <parameter>column</parameter> <type>integer</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the comment for a table column, which is specified by the OID
|
|
of its table and its column number.
|
|
(<function>obj_description</function> cannot be used for table
|
|
columns, since columns do not have OIDs of their own.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>obj_description</primary>
|
|
</indexterm>
|
|
<function>obj_description</function> ( <parameter>object</parameter> <type>oid</type>, <parameter>catalog</parameter> <type>name</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the comment for a database object specified by its OID and the
|
|
name of the containing system catalog. For
|
|
example, <literal>obj_description(123456, 'pg_class')</literal> would
|
|
retrieve the comment for the table with OID 123456.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>obj_description</function> ( <parameter>object</parameter> <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the comment for a database object specified by its OID alone.
|
|
This is <emphasis>deprecated</emphasis> since there is no guarantee
|
|
that OIDs are unique across different system catalogs; therefore, the
|
|
wrong comment might be returned.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>shobj_description</primary>
|
|
</indexterm>
|
|
<function>shobj_description</function> ( <parameter>object</parameter> <type>oid</type>, <parameter>catalog</parameter> <type>name</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the comment for a shared database object specified by its OID
|
|
and the name of the containing system catalog. This is just
|
|
like <function>obj_description</function> except that it is used for
|
|
retrieving comments on shared objects (that is, databases, roles, and
|
|
tablespaces). Some system catalogs are global to all databases within
|
|
each cluster, and the descriptions for objects in them are stored
|
|
globally as well.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-validity">
|
|
<title>Data Validity Checking Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-info-validity-table"/>
|
|
can be helpful for checking validity of proposed input data.
|
|
</para>
|
|
|
|
<table id="functions-info-validity-table">
|
|
<title>Data Validity Checking Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_input_is_valid</primary>
|
|
</indexterm>
|
|
<function>pg_input_is_valid</function> (
|
|
<parameter>string</parameter> <type>text</type>,
|
|
<parameter>type</parameter> <type>text</type>
|
|
)
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Tests whether the given <parameter>string</parameter> is valid
|
|
input for the specified data type, returning true or false.
|
|
</para>
|
|
<para>
|
|
This function will only work as desired if the data type's input
|
|
function has been updated to report invalid input as
|
|
a <quote>soft</quote> error. Otherwise, invalid input will abort
|
|
the transaction, just as if the string had been cast to the type
|
|
directly.
|
|
</para>
|
|
<para>
|
|
<literal>pg_input_is_valid('42', 'integer')</literal>
|
|
<returnvalue>t</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>pg_input_is_valid('42000000000', 'integer')</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para>
|
|
<para>
|
|
<literal>pg_input_is_valid('1234.567', 'numeric(7,4)')</literal>
|
|
<returnvalue>f</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_input_error_info</primary>
|
|
</indexterm>
|
|
<function>pg_input_error_info</function> (
|
|
<parameter>string</parameter> <type>text</type>,
|
|
<parameter>type</parameter> <type>text</type>
|
|
)
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>message</parameter> <type>text</type>,
|
|
<parameter>detail</parameter> <type>text</type>,
|
|
<parameter>hint</parameter> <type>text</type>,
|
|
<parameter>sql_error_code</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Tests whether the given <parameter>string</parameter> is valid
|
|
input for the specified data type; if not, return the details of
|
|
the error that would have been thrown. If the input is valid, the
|
|
results are NULL. The inputs are the same as
|
|
for <function>pg_input_is_valid</function>.
|
|
</para>
|
|
<para>
|
|
This function will only work as desired if the data type's input
|
|
function has been updated to report invalid input as
|
|
a <quote>soft</quote> error. Otherwise, invalid input will abort
|
|
the transaction, just as if the string had been cast to the type
|
|
directly.
|
|
</para>
|
|
<para>
|
|
<literal>select * from pg_input_error_info('42000000000', 'integer')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
message | detail | hint | sql_error_code
|
|
------------------------------------------------------+--------+------+----------------
|
|
value "42000000000" is out of range for type integer | | | 22003
|
|
</programlisting>
|
|
</para>
|
|
<para>
|
|
<literal>select message, detail from pg_input_error_info('1234.567', 'numeric(7,4)')</literal>
|
|
<returnvalue></returnvalue>
|
|
<programlisting>
|
|
message | detail
|
|
------------------------+----------------------------------&zwsp;-------------------------------------------------
|
|
numeric field overflow | A field with precision 7, scale 4 must round to an absolute value less than 10^3.
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-snapshot">
|
|
<title>Transaction ID and Snapshot Information Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-pg-snapshot"/>
|
|
provide server transaction information in an exportable form. The main
|
|
use of these functions is to determine which transactions were committed
|
|
between two snapshots.
|
|
</para>
|
|
|
|
<table id="functions-pg-snapshot">
|
|
<title>Transaction ID and Snapshot Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_current_xact_id</primary>
|
|
</indexterm>
|
|
<function>pg_current_xact_id</function> ()
|
|
<returnvalue>xid8</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the current transaction's ID. It will assign a new one if the
|
|
current transaction does not have one already (because it has not
|
|
performed any database updates); see <xref
|
|
linkend="transaction-id"/> for details. If executed in a
|
|
subtransaction, this will return the top-level transaction ID;
|
|
see <xref linkend="subxacts"/> for details.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_current_xact_id_if_assigned</primary>
|
|
</indexterm>
|
|
<function>pg_current_xact_id_if_assigned</function> ()
|
|
<returnvalue>xid8</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the current transaction's ID, or <literal>NULL</literal> if no
|
|
ID is assigned yet. (It's best to use this variant if the transaction
|
|
might otherwise be read-only, to avoid unnecessary consumption of an
|
|
XID.)
|
|
If executed in a subtransaction, this will return the top-level
|
|
transaction ID.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_xact_status</primary>
|
|
</indexterm>
|
|
<function>pg_xact_status</function> ( <type>xid8</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Reports the commit status of a recent transaction.
|
|
The result is one of <literal>in progress</literal>,
|
|
<literal>committed</literal>, or <literal>aborted</literal>,
|
|
provided that the transaction is recent enough that the system retains
|
|
the commit status of that transaction.
|
|
If it is old enough that no references to the transaction survive in
|
|
the system and the commit status information has been discarded, the
|
|
result is <literal>NULL</literal>.
|
|
Applications might use this function, for example, to determine
|
|
whether their transaction committed or aborted after the application
|
|
and database server become disconnected while
|
|
a <literal>COMMIT</literal> is in progress.
|
|
Note that prepared transactions are reported as <literal>in
|
|
progress</literal>; applications must check <link
|
|
linkend="view-pg-prepared-xacts"><structname>pg_prepared_xacts</structname></link>
|
|
if they need to determine whether a transaction ID belongs to a
|
|
prepared transaction.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_current_snapshot</primary>
|
|
</indexterm>
|
|
<function>pg_current_snapshot</function> ()
|
|
<returnvalue>pg_snapshot</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a current <firstterm>snapshot</firstterm>, a data structure
|
|
showing which transaction IDs are now in-progress.
|
|
Only top-level transaction IDs are included in the snapshot;
|
|
subtransaction IDs are not shown; see <xref linkend="subxacts"/>
|
|
for details.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_snapshot_xip</primary>
|
|
</indexterm>
|
|
<function>pg_snapshot_xip</function> ( <type>pg_snapshot</type> )
|
|
<returnvalue>setof xid8</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the set of in-progress transaction IDs contained in a snapshot.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_snapshot_xmax</primary>
|
|
</indexterm>
|
|
<function>pg_snapshot_xmax</function> ( <type>pg_snapshot</type> )
|
|
<returnvalue>xid8</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the <structfield>xmax</structfield> of a snapshot.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_snapshot_xmin</primary>
|
|
</indexterm>
|
|
<function>pg_snapshot_xmin</function> ( <type>pg_snapshot</type> )
|
|
<returnvalue>xid8</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the <structfield>xmin</structfield> of a snapshot.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_visible_in_snapshot</primary>
|
|
</indexterm>
|
|
<function>pg_visible_in_snapshot</function> ( <type>xid8</type>, <type>pg_snapshot</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Is the given transaction ID <firstterm>visible</firstterm> according
|
|
to this snapshot (that is, was it completed before the snapshot was
|
|
taken)? Note that this function will not give the correct answer for
|
|
a subtransaction ID (subxid); see <xref linkend="subxacts"/> for
|
|
details.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The internal transaction ID type <type>xid</type> is 32 bits wide and
|
|
wraps around every 4 billion transactions. However,
|
|
the functions shown in <xref linkend="functions-pg-snapshot"/> use a
|
|
64-bit type <type>xid8</type> that does not wrap around during the life
|
|
of an installation and can be converted to <type>xid</type> by casting if
|
|
required; see <xref linkend="transaction-id"/> for details.
|
|
The data type <type>pg_snapshot</type> stores information about
|
|
transaction ID visibility at a particular moment in time. Its components
|
|
are described in <xref linkend="functions-pg-snapshot-parts"/>.
|
|
<type>pg_snapshot</type>'s textual representation is
|
|
<literal><replaceable>xmin</replaceable>:<replaceable>xmax</replaceable>:<replaceable>xip_list</replaceable></literal>.
|
|
For example <literal>10:20:10,14,15</literal> means
|
|
<literal>xmin=10, xmax=20, xip_list=10, 14, 15</literal>.
|
|
</para>
|
|
|
|
<table id="functions-pg-snapshot-parts">
|
|
<title>Snapshot Components</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><structfield>xmin</structfield></entry>
|
|
<entry>
|
|
Lowest transaction ID that was still active. All transaction IDs
|
|
less than <structfield>xmin</structfield> are either committed and visible,
|
|
or rolled back and dead.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>xmax</structfield></entry>
|
|
<entry>
|
|
One past the highest completed transaction ID. All transaction IDs
|
|
greater than or equal to <structfield>xmax</structfield> had not yet
|
|
completed as of the time of the snapshot, and thus are invisible.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>xip_list</structfield></entry>
|
|
<entry>
|
|
Transactions in progress at the time of the snapshot. A transaction
|
|
ID that is <literal>xmin <= <replaceable>X</replaceable> <
|
|
xmax</literal> and not in this list was already completed at the time
|
|
of the snapshot, and thus is either visible or dead according to its
|
|
commit status. This list does not include the transaction IDs of
|
|
subtransactions (subxids).
|
|
</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
In releases of <productname>PostgreSQL</productname> before 13 there was
|
|
no <type>xid8</type> type, so variants of these functions were provided
|
|
that used <type>bigint</type> to represent a 64-bit XID, with a
|
|
correspondingly distinct snapshot data type <type>txid_snapshot</type>.
|
|
These older functions have <literal>txid</literal> in their names. They
|
|
are still supported for backward compatibility, but may be removed from a
|
|
future release. See <xref linkend="functions-txid-snapshot"/>.
|
|
</para>
|
|
|
|
<table id="functions-txid-snapshot">
|
|
<title>Deprecated Transaction ID and Snapshot Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>age</primary>
|
|
</indexterm>
|
|
<function>age</function> ( <type>xid</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of transactions between the supplied
|
|
transaction id and the current transaction counter.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>mxid_age</primary>
|
|
</indexterm>
|
|
<function>mxid_age</function> ( <type>xid</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the number of multixacts IDs between the supplied
|
|
multixact ID and the current multixacts counter.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>txid_current</primary>
|
|
</indexterm>
|
|
<function>txid_current</function> ()
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
See <function>pg_current_xact_id()</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>txid_current_if_assigned</primary>
|
|
</indexterm>
|
|
<function>txid_current_if_assigned</function> ()
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
See <function>pg_current_xact_id_if_assigned()</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>txid_current_snapshot</primary>
|
|
</indexterm>
|
|
<function>txid_current_snapshot</function> ()
|
|
<returnvalue>txid_snapshot</returnvalue>
|
|
</para>
|
|
<para>
|
|
See <function>pg_current_snapshot()</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>txid_snapshot_xip</primary>
|
|
</indexterm>
|
|
<function>txid_snapshot_xip</function> ( <type>txid_snapshot</type> )
|
|
<returnvalue>setof bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
See <function>pg_snapshot_xip()</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>txid_snapshot_xmax</primary>
|
|
</indexterm>
|
|
<function>txid_snapshot_xmax</function> ( <type>txid_snapshot</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
See <function>pg_snapshot_xmax()</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>txid_snapshot_xmin</primary>
|
|
</indexterm>
|
|
<function>txid_snapshot_xmin</function> ( <type>txid_snapshot</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
See <function>pg_snapshot_xmin()</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>txid_visible_in_snapshot</primary>
|
|
</indexterm>
|
|
<function>txid_visible_in_snapshot</function> ( <type>bigint</type>, <type>txid_snapshot</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
See <function>pg_visible_in_snapshot()</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>txid_status</primary>
|
|
</indexterm>
|
|
<function>txid_status</function> ( <type>bigint</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
See <function>pg_xact_status()</function>.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-commit-timestamp">
|
|
<title>Committed Transaction Information Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-commit-timestamp"/>
|
|
provide information about when past transactions were committed.
|
|
They only provide useful data when the
|
|
<xref linkend="guc-track-commit-timestamp"/> configuration option is
|
|
enabled, and only for transactions that were committed after it was
|
|
enabled. Commit timestamp information is routinely removed during
|
|
vacuum.
|
|
</para>
|
|
|
|
<table id="functions-commit-timestamp">
|
|
<title>Committed Transaction Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_xact_commit_timestamp</primary>
|
|
</indexterm>
|
|
<function>pg_xact_commit_timestamp</function> ( <type>xid</type> )
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the commit timestamp of a transaction.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_xact_commit_timestamp_origin</primary>
|
|
</indexterm>
|
|
<function>pg_xact_commit_timestamp_origin</function> ( <type>xid</type> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>timestamp</parameter> <type>timestamp with time zone</type>,
|
|
<parameter>roident</parameter> <type>oid</type>)
|
|
</para>
|
|
<para>
|
|
Returns the commit timestamp and replication origin of a transaction.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_last_committed_xact</primary>
|
|
</indexterm>
|
|
<function>pg_last_committed_xact</function> ()
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>xid</parameter> <type>xid</type>,
|
|
<parameter>timestamp</parameter> <type>timestamp with time zone</type>,
|
|
<parameter>roident</parameter> <type>oid</type> )
|
|
</para>
|
|
<para>
|
|
Returns the transaction ID, commit timestamp and replication origin
|
|
of the latest committed transaction.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-controldata">
|
|
<title>Control Data Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-controldata"/>
|
|
print information initialized during <command>initdb</command>, such
|
|
as the catalog version. They also show information about write-ahead
|
|
logging and checkpoint processing. This information is cluster-wide,
|
|
not specific to any one database. These functions provide most of the same
|
|
information, from the same source, as the
|
|
<xref linkend="app-pgcontroldata"/> application.
|
|
</para>
|
|
|
|
<table id="functions-controldata">
|
|
<title>Control Data Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_control_checkpoint</primary>
|
|
</indexterm>
|
|
<function>pg_control_checkpoint</function> ()
|
|
<returnvalue>record</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns information about current checkpoint state, as shown in
|
|
<xref linkend="functions-pg-control-checkpoint"/>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_control_system</primary>
|
|
</indexterm>
|
|
<function>pg_control_system</function> ()
|
|
<returnvalue>record</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns information about current control file state, as shown in
|
|
<xref linkend="functions-pg-control-system"/>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_control_init</primary>
|
|
</indexterm>
|
|
<function>pg_control_init</function> ()
|
|
<returnvalue>record</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns information about cluster initialization state, as shown in
|
|
<xref linkend="functions-pg-control-init"/>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_control_recovery</primary>
|
|
</indexterm>
|
|
<function>pg_control_recovery</function> ()
|
|
<returnvalue>record</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns information about recovery state, as shown in
|
|
<xref linkend="functions-pg-control-recovery"/>.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-pg-control-checkpoint">
|
|
<title><function>pg_control_checkpoint</function> Output Columns</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Column Name</entry>
|
|
<entry>Data Type</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
|
|
<row>
|
|
<entry><structfield>checkpoint_lsn</structfield></entry>
|
|
<entry><type>pg_lsn</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>redo_lsn</structfield></entry>
|
|
<entry><type>pg_lsn</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>redo_wal_file</structfield></entry>
|
|
<entry><type>text</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>timeline_id</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>prev_timeline_id</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>full_page_writes</structfield></entry>
|
|
<entry><type>boolean</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>next_xid</structfield></entry>
|
|
<entry><type>text</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>next_oid</structfield></entry>
|
|
<entry><type>oid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>next_multixact_id</structfield></entry>
|
|
<entry><type>xid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>next_multi_offset</structfield></entry>
|
|
<entry><type>xid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>oldest_xid</structfield></entry>
|
|
<entry><type>xid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>oldest_xid_dbid</structfield></entry>
|
|
<entry><type>oid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>oldest_active_xid</structfield></entry>
|
|
<entry><type>xid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>oldest_multi_xid</structfield></entry>
|
|
<entry><type>xid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>oldest_multi_dbid</structfield></entry>
|
|
<entry><type>oid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>oldest_commit_ts_xid</structfield></entry>
|
|
<entry><type>xid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>newest_commit_ts_xid</structfield></entry>
|
|
<entry><type>xid</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>checkpoint_time</structfield></entry>
|
|
<entry><type>timestamp with time zone</type></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-pg-control-system">
|
|
<title><function>pg_control_system</function> Output Columns</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Column Name</entry>
|
|
<entry>Data Type</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
|
|
<row>
|
|
<entry><structfield>pg_control_version</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>catalog_version_no</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>system_identifier</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>pg_control_last_modified</structfield></entry>
|
|
<entry><type>timestamp with time zone</type></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-pg-control-init">
|
|
<title><function>pg_control_init</function> Output Columns</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Column Name</entry>
|
|
<entry>Data Type</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
|
|
<row>
|
|
<entry><structfield>max_data_alignment</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>database_block_size</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>blocks_per_segment</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>wal_block_size</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>bytes_per_wal_segment</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>max_identifier_length</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>max_index_columns</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>max_toast_chunk_size</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>large_object_chunk_size</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>float8_pass_by_value</structfield></entry>
|
|
<entry><type>boolean</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>data_page_checksum_version</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-pg-control-recovery">
|
|
<title><function>pg_control_recovery</function> Output Columns</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Column Name</entry>
|
|
<entry>Data Type</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
|
|
<row>
|
|
<entry><structfield>min_recovery_end_lsn</structfield></entry>
|
|
<entry><type>pg_lsn</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>min_recovery_end_timeline</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>backup_start_lsn</structfield></entry>
|
|
<entry><type>pg_lsn</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>backup_end_lsn</structfield></entry>
|
|
<entry><type>pg_lsn</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>end_of_backup_record_required</structfield></entry>
|
|
<entry><type>boolean</type></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-version">
|
|
<title>Version Information Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-version"/>
|
|
print version information.
|
|
</para>
|
|
|
|
<table id="functions-version">
|
|
<title>Version Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>version</primary>
|
|
</indexterm>
|
|
<function>version</function> ()
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a string describing the <productname>PostgreSQL</productname>
|
|
server's version. You can also get this information from
|
|
<xref linkend="guc-server-version"/>, or for a machine-readable
|
|
version use <xref linkend="guc-server-version-num"/>. Software
|
|
developers should use <varname>server_version_num</varname> (available
|
|
since 8.2) or <xref linkend="libpq-PQserverVersion"/> instead of
|
|
parsing the text version.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>unicode_version</primary>
|
|
</indexterm>
|
|
<function>unicode_version</function> ()
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a string representing the version of Unicode used by
|
|
<productname>PostgreSQL</productname>.
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>icu_unicode_version</primary>
|
|
</indexterm>
|
|
<function>icu_unicode_version</function> ()
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a string representing the version of Unicode used by ICU, if
|
|
the server was built with ICU support; otherwise returns
|
|
<literal>NULL</literal> </para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-info-wal-summary">
|
|
<title>WAL Summarization Information Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-wal-summary"/>
|
|
print information about the status of WAL summarization.
|
|
See <xref linkend="guc-summarize-wal" />.
|
|
</para>
|
|
|
|
<table id="functions-wal-summary">
|
|
<title>WAL Summarization Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_available_wal_summaries</primary>
|
|
</indexterm>
|
|
<function>pg_available_wal_summaries</function> ()
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>tli</parameter> <type>bigint</type>,
|
|
<parameter>start_lsn</parameter> <type>pg_lsn</type>,
|
|
<parameter>end_lsn</parameter> <type>pg_lsn</type> )
|
|
</para>
|
|
<para>
|
|
Returns information about the WAL summary files present in the
|
|
data directory, under <literal>pg_wal/summaries</literal>.
|
|
One row will be returned per WAL summary file. Each file summarizes
|
|
WAL on the indicated TLI within the indicated LSN range. This function
|
|
might be useful to determine whether enough WAL summaries are present
|
|
on the server to take an incremental backup based on some prior
|
|
backup whose start LSN is known.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_wal_summary_contents</primary>
|
|
</indexterm>
|
|
<function>pg_wal_summary_contents</function> ( <parameter>tli</parameter> <type>bigint</type>, <parameter>start_lsn</parameter> <type>pg_lsn</type>, <parameter>end_lsn</parameter> <type>pg_lsn</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>relfilenode</parameter> <type>oid</type>,
|
|
<parameter>reltablespace</parameter> <type>oid</type>,
|
|
<parameter>reldatabase</parameter> <type>oid</type>,
|
|
<parameter>relforknumber</parameter> <type>smallint</type>,
|
|
<parameter>relblocknumber</parameter> <type>bigint</type>,
|
|
<parameter>is_limit_block</parameter> <type>boolean</type> )
|
|
</para>
|
|
<para>
|
|
Returns one information about the contents of a single WAL summary file
|
|
identified by TLI and starting and ending LSNs. Each row with
|
|
<literal>is_limit_block</literal> false indicates that the block
|
|
identified by the remaining output columns was modified by at least
|
|
one WAL record within the range of records summarized by this file.
|
|
Each row with <literal>is_limit_block</literal> true indicates either
|
|
that (a) the relation fork was truncated to the length given by
|
|
<literal>relblocknumber</literal> within the relevant range of WAL
|
|
records or (b) that the relation fork was created or dropped within
|
|
the relevant range of WAL records; in such cases,
|
|
<literal>relblocknumber</literal> will be zero.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_wal_summarizer_state</primary>
|
|
</indexterm>
|
|
<function>pg_get_wal_summarizer_state</function> ()
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>summarized_tli</parameter> <type>bigint</type>,
|
|
<parameter>summarized_lsn</parameter> <type>pg_lsn</type>,
|
|
<parameter>pending_lsn</parameter> <type>pg_lsn</type>,
|
|
<parameter>summarizer_pid</parameter> <type>int</type> )
|
|
</para>
|
|
<para>
|
|
Returns information about the progress of the WAL summarizer. If the
|
|
WAL summarizer has never run since the instance was started, then
|
|
<literal>summarized_tli</literal> and <literal>summarized_lsn</literal>
|
|
will be <literal>0</literal> and <literal>0/0</literal> respectively;
|
|
otherwise, they will be the TLI and ending LSN of the last WAL summary
|
|
file written to disk. If the WAL summarizer is currently running,
|
|
<literal>pending_lsn</literal> will be the ending LSN of the last
|
|
record that it has consumed, which must always be greater than or
|
|
equal to <literal>summarized_lsn</literal>; if the WAL summarizer is
|
|
not running, it will be equal to <literal>summarized_lsn</literal>.
|
|
<literal>summarizer_pid</literal> is the PID of the WAL summarizer
|
|
process, if it is running, and otherwise NULL.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="functions-admin">
|
|
<title>System Administration Functions</title>
|
|
|
|
<para>
|
|
The functions described in this section are used to control and
|
|
monitor a <productname>PostgreSQL</productname> installation.
|
|
</para>
|
|
|
|
<sect2 id="functions-admin-set">
|
|
<title>Configuration Settings Functions</title>
|
|
|
|
<indexterm>
|
|
<primary>SET</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>SHOW</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>configuration</primary>
|
|
<secondary sortas="server">of the server</secondary>
|
|
<tertiary>functions</tertiary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<xref linkend="functions-admin-set-table"/> shows the functions
|
|
available to query and alter run-time configuration parameters.
|
|
</para>
|
|
|
|
<table id="functions-admin-set-table">
|
|
<title>Configuration Settings Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example(s)
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>current_setting</primary>
|
|
</indexterm>
|
|
<function>current_setting</function> ( <parameter>setting_name</parameter> <type>text</type> <optional>, <parameter>missing_ok</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the current value of the
|
|
setting <parameter>setting_name</parameter>. If there is no such
|
|
setting, <function>current_setting</function> throws an error
|
|
unless <parameter>missing_ok</parameter> is supplied and
|
|
is <literal>true</literal> (in which case NULL is returned).
|
|
This function corresponds to
|
|
the <acronym>SQL</acronym> command <xref linkend="sql-show"/>.
|
|
</para>
|
|
<para>
|
|
<literal>current_setting('datestyle')</literal>
|
|
<returnvalue>ISO, MDY</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>set_config</primary>
|
|
</indexterm>
|
|
<function>set_config</function> (
|
|
<parameter>setting_name</parameter> <type>text</type>,
|
|
<parameter>new_value</parameter> <type>text</type>,
|
|
<parameter>is_local</parameter> <type>boolean</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets the parameter <parameter>setting_name</parameter>
|
|
to <parameter>new_value</parameter>, and returns that value.
|
|
If <parameter>is_local</parameter> is <literal>true</literal>, the new
|
|
value will only apply during the current transaction. If you want the
|
|
new value to apply for the rest of the current session,
|
|
use <literal>false</literal> instead. This function corresponds to
|
|
the SQL command <xref linkend="sql-set"/>.
|
|
</para>
|
|
<para>
|
|
<literal>set_config('log_statement_stats', 'off', false)</literal>
|
|
<returnvalue>off</returnvalue>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-admin-signal">
|
|
<title>Server Signaling Functions</title>
|
|
|
|
<indexterm>
|
|
<primary>signal</primary>
|
|
<secondary sortas="backend">backend processes</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The functions shown in <xref
|
|
linkend="functions-admin-signal-table"/> send control signals to
|
|
other server processes. Use of these functions is restricted to
|
|
superusers by default but access may be granted to others using
|
|
<command>GRANT</command>, with noted exceptions.
|
|
</para>
|
|
|
|
<para>
|
|
Each of these functions returns <literal>true</literal> if
|
|
the signal was successfully sent and <literal>false</literal>
|
|
if sending the signal failed.
|
|
</para>
|
|
|
|
<table id="functions-admin-signal-table">
|
|
<title>Server Signaling Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_cancel_backend</primary>
|
|
</indexterm>
|
|
<function>pg_cancel_backend</function> ( <parameter>pid</parameter> <type>integer</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cancels the current query of the session whose backend process has the
|
|
specified process ID. This is also allowed if the
|
|
calling role is a member of the role whose backend is being canceled or
|
|
the calling role has privileges of <literal>pg_signal_backend</literal>,
|
|
however only superusers can cancel superuser backends.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_log_backend_memory_contexts</primary>
|
|
</indexterm>
|
|
<function>pg_log_backend_memory_contexts</function> ( <parameter>pid</parameter> <type>integer</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Requests to log the memory contexts of the backend with the
|
|
specified process ID. This function can send the request to
|
|
backends and auxiliary processes except logger. These memory contexts
|
|
will be logged at
|
|
<literal>LOG</literal> message level. They will appear in
|
|
the server log based on the log configuration set
|
|
(see <xref linkend="runtime-config-logging"/> for more information),
|
|
but will not be sent to the client regardless of
|
|
<xref linkend="guc-client-min-messages"/>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_reload_conf</primary>
|
|
</indexterm>
|
|
<function>pg_reload_conf</function> ()
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Causes all processes of the <productname>PostgreSQL</productname>
|
|
server to reload their configuration files. (This is initiated by
|
|
sending a <systemitem>SIGHUP</systemitem> signal to the postmaster
|
|
process, which in turn sends <systemitem>SIGHUP</systemitem> to each
|
|
of its children.) You can use the
|
|
<link linkend="view-pg-file-settings"><structname>pg_file_settings</structname></link>,
|
|
<link linkend="view-pg-hba-file-rules"><structname>pg_hba_file_rules</structname></link> and
|
|
<link linkend="view-pg-ident-file-mappings"><structname>pg_ident_file_mappings</structname></link> views
|
|
to check the configuration files for possible errors, before reloading.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_rotate_logfile</primary>
|
|
</indexterm>
|
|
<function>pg_rotate_logfile</function> ()
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Signals the log-file manager to switch to a new output file
|
|
immediately. This works only when the built-in log collector is
|
|
running, since otherwise there is no log-file manager subprocess.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_terminate_backend</primary>
|
|
</indexterm>
|
|
<function>pg_terminate_backend</function> ( <parameter>pid</parameter> <type>integer</type>, <parameter>timeout</parameter> <type>bigint</type> <literal>DEFAULT</literal> <literal>0</literal> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Terminates the session whose backend process has the
|
|
specified process ID. This is also allowed if the calling role
|
|
is a member of the role whose backend is being terminated or the
|
|
calling role has privileges of <literal>pg_signal_backend</literal>,
|
|
however only superusers can terminate superuser backends.
|
|
</para>
|
|
<para>
|
|
If <parameter>timeout</parameter> is not specified or zero, this
|
|
function returns <literal>true</literal> whether the process actually
|
|
terminates or not, indicating only that the sending of the signal was
|
|
successful. If the <parameter>timeout</parameter> is specified (in
|
|
milliseconds) and greater than zero, the function waits until the
|
|
process is actually terminated or until the given time has passed. If
|
|
the process is terminated, the function
|
|
returns <literal>true</literal>. On timeout, a warning is emitted and
|
|
<literal>false</literal> is returned.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<function>pg_cancel_backend</function> and <function>pg_terminate_backend</function>
|
|
send signals (<systemitem>SIGINT</systemitem> or <systemitem>SIGTERM</systemitem>
|
|
respectively) to backend processes identified by process ID.
|
|
The process ID of an active backend can be found from
|
|
the <structfield>pid</structfield> column of the
|
|
<structname>pg_stat_activity</structname> view, or by listing the
|
|
<command>postgres</command> processes on the server (using
|
|
<application>ps</application> on Unix or the <application>Task
|
|
Manager</application> on <productname>Windows</productname>).
|
|
The role of an active backend can be found from the
|
|
<structfield>usename</structfield> column of the
|
|
<structname>pg_stat_activity</structname> view.
|
|
</para>
|
|
|
|
<para>
|
|
<function>pg_log_backend_memory_contexts</function> can be used
|
|
to log the memory contexts of a backend process. For example:
|
|
<programlisting>
|
|
postgres=# SELECT pg_log_backend_memory_contexts(pg_backend_pid());
|
|
pg_log_backend_memory_contexts
|
|
--------------------------------
|
|
t
|
|
(1 row)
|
|
</programlisting>
|
|
One message for each memory context will be logged. For example:
|
|
<screen>
|
|
LOG: logging memory contexts of PID 10377
|
|
STATEMENT: SELECT pg_log_backend_memory_contexts(pg_backend_pid());
|
|
LOG: level: 0; TopMemoryContext: 80800 total in 6 blocks; 14432 free (5 chunks); 66368 used
|
|
LOG: level: 1; pgstat TabStatusArray lookup hash table: 8192 total in 1 blocks; 1408 free (0 chunks); 6784 used
|
|
LOG: level: 1; TopTransactionContext: 8192 total in 1 blocks; 7720 free (1 chunks); 472 used
|
|
LOG: level: 1; RowDescriptionContext: 8192 total in 1 blocks; 6880 free (0 chunks); 1312 used
|
|
LOG: level: 1; MessageContext: 16384 total in 2 blocks; 5152 free (0 chunks); 11232 used
|
|
LOG: level: 1; Operator class cache: 8192 total in 1 blocks; 512 free (0 chunks); 7680 used
|
|
LOG: level: 1; smgr relation table: 16384 total in 2 blocks; 4544 free (3 chunks); 11840 used
|
|
LOG: level: 1; TransactionAbortContext: 32768 total in 1 blocks; 32504 free (0 chunks); 264 used
|
|
...
|
|
LOG: level: 1; ErrorContext: 8192 total in 1 blocks; 7928 free (3 chunks); 264 used
|
|
LOG: Grand total: 1651920 bytes in 201 blocks; 622360 free (88 chunks); 1029560 used
|
|
</screen>
|
|
If there are more than 100 child contexts under the same parent, the first
|
|
100 child contexts are logged, along with a summary of the remaining contexts.
|
|
Note that frequent calls to this function could incur significant overhead,
|
|
because it may generate a large number of log messages.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-admin-backup">
|
|
<title>Backup Control Functions</title>
|
|
|
|
<indexterm>
|
|
<primary>backup</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The functions shown in <xref
|
|
linkend="functions-admin-backup-table"/> assist in making on-line backups.
|
|
These functions cannot be executed during recovery (except
|
|
<function>pg_backup_start</function>,
|
|
<function>pg_backup_stop</function>,
|
|
and <function>pg_wal_lsn_diff</function>).
|
|
</para>
|
|
|
|
<para>
|
|
For details about proper usage of these functions, see
|
|
<xref linkend="continuous-archiving"/>.
|
|
</para>
|
|
|
|
<table id="functions-admin-backup-table">
|
|
<title>Backup Control Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_create_restore_point</primary>
|
|
</indexterm>
|
|
<function>pg_create_restore_point</function> ( <parameter>name</parameter> <type>text</type> )
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Creates a named marker record in the write-ahead log that can later be
|
|
used as a recovery target, and returns the corresponding write-ahead
|
|
log location. The given name can then be used with
|
|
<xref linkend="guc-recovery-target-name"/> to specify the point up to
|
|
which recovery will proceed. Avoid creating multiple restore points
|
|
with the same name, since recovery will stop at the first one whose
|
|
name matches the recovery target.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_current_wal_flush_lsn</primary>
|
|
</indexterm>
|
|
<function>pg_current_wal_flush_lsn</function> ()
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the current write-ahead log flush location (see notes below).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_current_wal_insert_lsn</primary>
|
|
</indexterm>
|
|
<function>pg_current_wal_insert_lsn</function> ()
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the current write-ahead log insert location (see notes below).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_current_wal_lsn</primary>
|
|
</indexterm>
|
|
<function>pg_current_wal_lsn</function> ()
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the current write-ahead log write location (see notes below).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_backup_start</primary>
|
|
</indexterm>
|
|
<function>pg_backup_start</function> (
|
|
<parameter>label</parameter> <type>text</type>
|
|
<optional>, <parameter>fast</parameter> <type>boolean</type>
|
|
</optional> )
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Prepares the server to begin an on-line backup. The only required
|
|
parameter is an arbitrary user-defined label for the backup.
|
|
(Typically this would be the name under which the backup dump file
|
|
will be stored.)
|
|
If the optional second parameter is given as <literal>true</literal>,
|
|
it specifies executing <function>pg_backup_start</function> as quickly
|
|
as possible. This forces an immediate checkpoint which will cause a
|
|
spike in I/O operations, slowing any concurrently executing queries.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_backup_stop</primary>
|
|
</indexterm>
|
|
<function>pg_backup_stop</function> (
|
|
<optional><parameter>wait_for_archive</parameter> <type>boolean</type>
|
|
</optional> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>lsn</parameter> <type>pg_lsn</type>,
|
|
<parameter>labelfile</parameter> <type>text</type>,
|
|
<parameter>spcmapfile</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Finishes performing an on-line backup. The desired contents of the
|
|
backup label file and the tablespace map file are returned as part of
|
|
the result of the function and must be written to files in the
|
|
backup area. These files must not be written to the live data directory
|
|
(doing so will cause PostgreSQL to fail to restart in the event of a
|
|
crash).
|
|
</para>
|
|
<para>
|
|
There is an optional parameter of type <type>boolean</type>.
|
|
If false, the function will return immediately after the backup is
|
|
completed, without waiting for WAL to be archived. This behavior is
|
|
only useful with backup software that independently monitors WAL
|
|
archiving. Otherwise, WAL required to make the backup consistent might
|
|
be missing and make the backup useless. By default or when this
|
|
parameter is true, <function>pg_backup_stop</function> will wait for
|
|
WAL to be archived when archiving is enabled. (On a standby, this
|
|
means that it will wait only when <varname>archive_mode</varname> =
|
|
<literal>always</literal>. If write activity on the primary is low,
|
|
it may be useful to run <function>pg_switch_wal</function> on the
|
|
primary in order to trigger an immediate segment switch.)
|
|
</para>
|
|
<para>
|
|
When executed on a primary, this function also creates a backup
|
|
history file in the write-ahead log archive area. The history file
|
|
includes the label given to <function>pg_backup_start</function>, the
|
|
starting and ending write-ahead log locations for the backup, and the
|
|
starting and ending times of the backup. After recording the ending
|
|
location, the current write-ahead log insertion point is automatically
|
|
advanced to the next write-ahead log file, so that the ending
|
|
write-ahead log file can be archived immediately to complete the
|
|
backup.
|
|
</para>
|
|
<para>
|
|
The result of the function is a single record.
|
|
The <parameter>lsn</parameter> column holds the backup's ending
|
|
write-ahead log location (which again can be ignored). The second
|
|
column returns the contents of the backup label file, and the third
|
|
column returns the contents of the tablespace map file. These must be
|
|
stored as part of the backup and are required as part of the restore
|
|
process.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_switch_wal</primary>
|
|
</indexterm>
|
|
<function>pg_switch_wal</function> ()
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Forces the server to switch to a new write-ahead log file, which
|
|
allows the current file to be archived (assuming you are using
|
|
continuous archiving). The result is the ending write-ahead log
|
|
location plus 1 within the just-completed write-ahead log file. If
|
|
there has been no write-ahead log activity since the last write-ahead
|
|
log switch, <function>pg_switch_wal</function> does nothing and
|
|
returns the start location of the write-ahead log file currently in
|
|
use.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_walfile_name</primary>
|
|
</indexterm>
|
|
<function>pg_walfile_name</function> ( <parameter>lsn</parameter> <type>pg_lsn</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts a write-ahead log location to the name of the WAL file
|
|
holding that location.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_walfile_name_offset</primary>
|
|
</indexterm>
|
|
<function>pg_walfile_name_offset</function> ( <parameter>lsn</parameter> <type>pg_lsn</type> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>file_name</parameter> <type>text</type>,
|
|
<parameter>file_offset</parameter> <type>integer</type> )
|
|
</para>
|
|
<para>
|
|
Converts a write-ahead log location to a WAL file name and byte offset
|
|
within that file.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_split_walfile_name</primary>
|
|
</indexterm>
|
|
<function>pg_split_walfile_name</function> ( <parameter>file_name</parameter> <type>text</type> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>segment_number</parameter> <type>numeric</type>,
|
|
<parameter>timeline_id</parameter> <type>bigint</type> )
|
|
</para>
|
|
<para>
|
|
Extracts the sequence number and timeline ID from a WAL file
|
|
name.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_wal_lsn_diff</primary>
|
|
</indexterm>
|
|
<function>pg_wal_lsn_diff</function> ( <parameter>lsn1</parameter> <type>pg_lsn</type>, <parameter>lsn2</parameter> <type>pg_lsn</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para>
|
|
Calculates the difference in bytes (<parameter>lsn1</parameter> - <parameter>lsn2</parameter>) between two write-ahead log
|
|
locations. This can be used
|
|
with <structname>pg_stat_replication</structname> or some of the
|
|
functions shown in <xref linkend="functions-admin-backup-table"/> to
|
|
get the replication lag.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<function>pg_current_wal_lsn</function> displays the current write-ahead
|
|
log write location in the same format used by the above functions.
|
|
Similarly, <function>pg_current_wal_insert_lsn</function> displays the
|
|
current write-ahead log insertion location
|
|
and <function>pg_current_wal_flush_lsn</function> displays the current
|
|
write-ahead log flush location. The insertion location is
|
|
the <quote>logical</quote> end of the write-ahead log at any instant,
|
|
while the write location is the end of what has actually been written out
|
|
from the server's internal buffers, and the flush location is the last
|
|
location known to be written to durable storage. The write location is the
|
|
end of what can be examined from outside the server, and is usually what
|
|
you want if you are interested in archiving partially-complete write-ahead
|
|
log files. The insertion and flush locations are made available primarily
|
|
for server debugging purposes. These are all read-only operations and do
|
|
not require superuser permissions.
|
|
</para>
|
|
|
|
<para>
|
|
You can use <function>pg_walfile_name_offset</function> to extract the
|
|
corresponding write-ahead log file name and byte offset from
|
|
a <type>pg_lsn</type> value. For example:
|
|
<programlisting>
|
|
postgres=# SELECT * FROM pg_walfile_name_offset((pg_backup_stop()).lsn);
|
|
file_name | file_offset
|
|
--------------------------+-------------
|
|
00000001000000000000000D | 4039624
|
|
(1 row)
|
|
</programlisting>
|
|
Similarly, <function>pg_walfile_name</function> extracts just the write-ahead log file name.
|
|
</para>
|
|
|
|
<para>
|
|
<function>pg_split_walfile_name</function> is useful to compute a
|
|
<acronym>LSN</acronym> from a file offset and WAL file name, for example:
|
|
<programlisting>
|
|
postgres=# \set file_name '000000010000000100C000AB'
|
|
postgres=# \set offset 256
|
|
postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset AS lsn
|
|
FROM pg_split_walfile_name(:'file_name') pd,
|
|
pg_show_all_settings() ps
|
|
WHERE ps.name = 'wal_segment_size';
|
|
lsn
|
|
---------------
|
|
C001/AB000100
|
|
(1 row)
|
|
</programlisting>
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-recovery-control">
|
|
<title>Recovery Control Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref
|
|
linkend="functions-recovery-info-table"/> provide information
|
|
about the current status of a standby server.
|
|
These functions may be executed both during recovery and in normal running.
|
|
</para>
|
|
|
|
<table id="functions-recovery-info-table">
|
|
<title>Recovery Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_is_in_recovery</primary>
|
|
</indexterm>
|
|
<function>pg_is_in_recovery</function> ()
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns true if recovery is still in progress.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_last_wal_receive_lsn</primary>
|
|
</indexterm>
|
|
<function>pg_last_wal_receive_lsn</function> ()
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the last write-ahead log location that has been received and
|
|
synced to disk by streaming replication. While streaming replication
|
|
is in progress this will increase monotonically. If recovery has
|
|
completed then this will remain static at the location of the last WAL
|
|
record received and synced to disk during recovery. If streaming
|
|
replication is disabled, or if it has not yet started, the function
|
|
returns <literal>NULL</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_last_wal_replay_lsn</primary>
|
|
</indexterm>
|
|
<function>pg_last_wal_replay_lsn</function> ()
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the last write-ahead log location that has been replayed
|
|
during recovery. If recovery is still in progress this will increase
|
|
monotonically. If recovery has completed then this will remain
|
|
static at the location of the last WAL record applied during recovery.
|
|
When the server has been started normally without recovery, the
|
|
function returns <literal>NULL</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_last_xact_replay_timestamp</primary>
|
|
</indexterm>
|
|
<function>pg_last_xact_replay_timestamp</function> ()
|
|
<returnvalue>timestamp with time zone</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the time stamp of the last transaction replayed during
|
|
recovery. This is the time at which the commit or abort WAL record
|
|
for that transaction was generated on the primary. If no transactions
|
|
have been replayed during recovery, the function
|
|
returns <literal>NULL</literal>. Otherwise, if recovery is still in
|
|
progress this will increase monotonically. If recovery has completed
|
|
then this will remain static at the time of the last transaction
|
|
applied during recovery. When the server has been started normally
|
|
without recovery, the function returns <literal>NULL</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_wal_resource_managers</primary>
|
|
</indexterm>
|
|
<function>pg_get_wal_resource_managers</function> ()
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>rm_id</parameter> <type>integer</type>,
|
|
<parameter>rm_name</parameter> <type>text</type>,
|
|
<parameter>rm_builtin</parameter> <type>boolean</type> )
|
|
</para>
|
|
<para>
|
|
Returns the currently-loaded WAL resource managers in the system. The
|
|
column <parameter>rm_builtin</parameter> indicates whether it's a
|
|
built-in resource manager, or a custom resource manager loaded by an
|
|
extension.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The functions shown in <xref
|
|
linkend="functions-recovery-control-table"/> control the progress of recovery.
|
|
These functions may be executed only during recovery.
|
|
</para>
|
|
|
|
<table id="functions-recovery-control-table">
|
|
<title>Recovery Control Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_is_wal_replay_paused</primary>
|
|
</indexterm>
|
|
<function>pg_is_wal_replay_paused</function> ()
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns true if recovery pause is requested.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_get_wal_replay_pause_state</primary>
|
|
</indexterm>
|
|
<function>pg_get_wal_replay_pause_state</function> ()
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns recovery pause state. The return values are <literal>
|
|
not paused</literal> if pause is not requested, <literal>
|
|
pause requested</literal> if pause is requested but recovery is
|
|
not yet paused, and <literal>paused</literal> if the recovery is
|
|
actually paused.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_promote</primary>
|
|
</indexterm>
|
|
<function>pg_promote</function> ( <parameter>wait</parameter> <type>boolean</type> <literal>DEFAULT</literal> <literal>true</literal>, <parameter>wait_seconds</parameter> <type>integer</type> <literal>DEFAULT</literal> <literal>60</literal> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Promotes a standby server to primary status.
|
|
With <parameter>wait</parameter> set to <literal>true</literal> (the
|
|
default), the function waits until promotion is completed
|
|
or <parameter>wait_seconds</parameter> seconds have passed, and
|
|
returns <literal>true</literal> if promotion is successful
|
|
and <literal>false</literal> otherwise.
|
|
If <parameter>wait</parameter> is set to <literal>false</literal>, the
|
|
function returns <literal>true</literal> immediately after sending a
|
|
<literal>SIGUSR1</literal> signal to the postmaster to trigger
|
|
promotion.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_wal_replay_pause</primary>
|
|
</indexterm>
|
|
<function>pg_wal_replay_pause</function> ()
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Request to pause recovery. A request doesn't mean that recovery stops
|
|
right away. If you want a guarantee that recovery is actually paused,
|
|
you need to check for the recovery pause state returned by
|
|
<function>pg_get_wal_replay_pause_state()</function>. Note that
|
|
<function>pg_is_wal_replay_paused()</function> returns whether a request
|
|
is made. While recovery is paused, no further database changes are applied.
|
|
If hot standby is active, all new queries will see the same consistent
|
|
snapshot of the database, and no further query conflicts will be generated
|
|
until recovery is resumed.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_wal_replay_resume</primary>
|
|
</indexterm>
|
|
<function>pg_wal_replay_resume</function> ()
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Restarts recovery if it was paused.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<function>pg_wal_replay_pause</function> and
|
|
<function>pg_wal_replay_resume</function> cannot be executed while
|
|
a promotion is ongoing. If a promotion is triggered while recovery
|
|
is paused, the paused state ends and promotion continues.
|
|
</para>
|
|
|
|
<para>
|
|
If streaming replication is disabled, the paused state may continue
|
|
indefinitely without a problem. If streaming replication is in
|
|
progress then WAL records will continue to be received, which will
|
|
eventually fill available disk space, depending upon the duration of
|
|
the pause, the rate of WAL generation and available disk space.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-snapshot-synchronization">
|
|
<title>Snapshot Synchronization Functions</title>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> allows database sessions to synchronize their
|
|
snapshots. A <firstterm>snapshot</firstterm> determines which data is visible to the
|
|
transaction that is using the snapshot. Synchronized snapshots are
|
|
necessary when two or more sessions need to see identical content in the
|
|
database. If two sessions just start their transactions independently,
|
|
there is always a possibility that some third transaction commits
|
|
between the executions of the two <command>START TRANSACTION</command> commands,
|
|
so that one session sees the effects of that transaction and the other
|
|
does not.
|
|
</para>
|
|
|
|
<para>
|
|
To solve this problem, <productname>PostgreSQL</productname> allows a transaction to
|
|
<firstterm>export</firstterm> the snapshot it is using. As long as the exporting
|
|
transaction remains open, other transactions can <firstterm>import</firstterm> its
|
|
snapshot, and thereby be guaranteed that they see exactly the same view
|
|
of the database that the first transaction sees. But note that any
|
|
database changes made by any one of these transactions remain invisible
|
|
to the other transactions, as is usual for changes made by uncommitted
|
|
transactions. So the transactions are synchronized with respect to
|
|
pre-existing data, but act normally for changes they make themselves.
|
|
</para>
|
|
|
|
<para>
|
|
Snapshots are exported with the <function>pg_export_snapshot</function> function,
|
|
shown in <xref linkend="functions-snapshot-synchronization-table"/>, and
|
|
imported with the <xref linkend="sql-set-transaction"/> command.
|
|
</para>
|
|
|
|
<table id="functions-snapshot-synchronization-table">
|
|
<title>Snapshot Synchronization Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_export_snapshot</primary>
|
|
</indexterm>
|
|
<function>pg_export_snapshot</function> ()
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Saves the transaction's current snapshot and returns
|
|
a <type>text</type> string identifying the snapshot. This string must
|
|
be passed (outside the database) to clients that want to import the
|
|
snapshot. The snapshot is available for import only until the end of
|
|
the transaction that exported it.
|
|
</para>
|
|
<para>
|
|
A transaction can export more than one snapshot, if needed. Note that
|
|
doing so is only useful in <literal>READ COMMITTED</literal>
|
|
transactions, since in <literal>REPEATABLE READ</literal> and higher
|
|
isolation levels, transactions use the same snapshot throughout their
|
|
lifetime. Once a transaction has exported any snapshots, it cannot be
|
|
prepared with <xref linkend="sql-prepare-transaction"/>.
|
|
</para></entry>
|
|
</row>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_log_standby_snapshot</primary>
|
|
</indexterm>
|
|
<function>pg_log_standby_snapshot</function> ()
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Take a snapshot of running transactions and write it to WAL, without
|
|
having to wait for bgwriter or checkpointer to log one. This is useful
|
|
for logical decoding on standby, as logical slot creation has to wait
|
|
until such a record is replayed on the standby.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-replication">
|
|
<title>Replication Management Functions</title>
|
|
|
|
<para>
|
|
The functions shown
|
|
in <xref linkend="functions-replication-table"/> are for
|
|
controlling and interacting with replication features.
|
|
See <xref linkend="streaming-replication"/>,
|
|
<xref linkend="streaming-replication-slots"/>, and
|
|
<xref linkend="replication-origins"/>
|
|
for information about the underlying features.
|
|
Use of functions for replication origin is only allowed to the
|
|
superuser by default, but may be allowed to other users by using the
|
|
<literal>GRANT</literal> command.
|
|
Use of functions for replication slots is restricted to superusers
|
|
and users having <literal>REPLICATION</literal> privilege.
|
|
</para>
|
|
|
|
<para>
|
|
Many of these functions have equivalent commands in the replication
|
|
protocol; see <xref linkend="protocol-replication"/>.
|
|
</para>
|
|
|
|
<para>
|
|
The functions described in
|
|
<xref linkend="functions-admin-backup"/>,
|
|
<xref linkend="functions-recovery-control"/>, and
|
|
<xref linkend="functions-snapshot-synchronization"/>
|
|
are also relevant for replication.
|
|
</para>
|
|
|
|
<table id="functions-replication-table">
|
|
<title>Replication Management Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_create_physical_replication_slot</primary>
|
|
</indexterm>
|
|
<function>pg_create_physical_replication_slot</function> ( <parameter>slot_name</parameter> <type>name</type> <optional>, <parameter>immediately_reserve</parameter> <type>boolean</type>, <parameter>temporary</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>slot_name</parameter> <type>name</type>,
|
|
<parameter>lsn</parameter> <type>pg_lsn</type> )
|
|
</para>
|
|
<para>
|
|
Creates a new physical replication slot named
|
|
<parameter>slot_name</parameter>. The optional second parameter,
|
|
when <literal>true</literal>, specifies that the <acronym>LSN</acronym> for this
|
|
replication slot be reserved immediately; otherwise
|
|
the <acronym>LSN</acronym> is reserved on first connection from a streaming
|
|
replication client. Streaming changes from a physical slot is only
|
|
possible with the streaming-replication protocol —
|
|
see <xref linkend="protocol-replication"/>. The optional third
|
|
parameter, <parameter>temporary</parameter>, when set to true, specifies that
|
|
the slot should not be permanently stored to disk and is only meant
|
|
for use by the current session. Temporary slots are also
|
|
released upon any error. This function corresponds
|
|
to the replication protocol command <literal>CREATE_REPLICATION_SLOT
|
|
... PHYSICAL</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_drop_replication_slot</primary>
|
|
</indexterm>
|
|
<function>pg_drop_replication_slot</function> ( <parameter>slot_name</parameter> <type>name</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Drops the physical or logical replication slot
|
|
named <parameter>slot_name</parameter>. Same as replication protocol
|
|
command <literal>DROP_REPLICATION_SLOT</literal>. For logical slots, this must
|
|
be called while connected to the same database the slot was created on.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-create-logical-replication-slot" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_create_logical_replication_slot</primary>
|
|
</indexterm>
|
|
<function>pg_create_logical_replication_slot</function> ( <parameter>slot_name</parameter> <type>name</type>, <parameter>plugin</parameter> <type>name</type> <optional>, <parameter>temporary</parameter> <type>boolean</type>, <parameter>twophase</parameter> <type>boolean</type>, <parameter>failover</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>slot_name</parameter> <type>name</type>,
|
|
<parameter>lsn</parameter> <type>pg_lsn</type> )
|
|
</para>
|
|
<para>
|
|
Creates a new logical (decoding) replication slot named
|
|
<parameter>slot_name</parameter> using the output plugin
|
|
<parameter>plugin</parameter>. The optional third
|
|
parameter, <parameter>temporary</parameter>, when set to true, specifies that
|
|
the slot should not be permanently stored to disk and is only meant
|
|
for use by the current session. Temporary slots are also
|
|
released upon any error. The optional fourth parameter,
|
|
<parameter>twophase</parameter>, when set to true, specifies
|
|
that the decoding of prepared transactions is enabled for this
|
|
slot. The optional fifth parameter,
|
|
<parameter>failover</parameter>, when set to true,
|
|
specifies that this slot is enabled to be synced to the
|
|
standbys so that logical replication can be resumed after
|
|
failover. A call to this function has the same effect as
|
|
the replication protocol command
|
|
<literal>CREATE_REPLICATION_SLOT ... LOGICAL</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_copy_physical_replication_slot</primary>
|
|
</indexterm>
|
|
<function>pg_copy_physical_replication_slot</function> ( <parameter>src_slot_name</parameter> <type>name</type>, <parameter>dst_slot_name</parameter> <type>name</type> <optional>, <parameter>temporary</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>slot_name</parameter> <type>name</type>,
|
|
<parameter>lsn</parameter> <type>pg_lsn</type> )
|
|
</para>
|
|
<para>
|
|
Copies an existing physical replication slot named <parameter>src_slot_name</parameter>
|
|
to a physical replication slot named <parameter>dst_slot_name</parameter>.
|
|
The copied physical slot starts to reserve WAL from the same <acronym>LSN</acronym> as the
|
|
source slot.
|
|
<parameter>temporary</parameter> is optional. If <parameter>temporary</parameter>
|
|
is omitted, the same value as the source slot is used.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_copy_logical_replication_slot</primary>
|
|
</indexterm>
|
|
<function>pg_copy_logical_replication_slot</function> ( <parameter>src_slot_name</parameter> <type>name</type>, <parameter>dst_slot_name</parameter> <type>name</type> <optional>, <parameter>temporary</parameter> <type>boolean</type> <optional>, <parameter>plugin</parameter> <type>name</type> </optional></optional> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>slot_name</parameter> <type>name</type>,
|
|
<parameter>lsn</parameter> <type>pg_lsn</type> )
|
|
</para>
|
|
<para>
|
|
Copies an existing logical replication slot
|
|
named <parameter>src_slot_name</parameter> to a logical replication
|
|
slot named <parameter>dst_slot_name</parameter>, optionally changing
|
|
the output plugin and persistence. The copied logical slot starts
|
|
from the same <acronym>LSN</acronym> as the source logical slot. Both
|
|
<parameter>temporary</parameter> and <parameter>plugin</parameter> are
|
|
optional; if they are omitted, the values of the source slot are used.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-logical-slot-get-changes" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_logical_slot_get_changes</primary>
|
|
</indexterm>
|
|
<function>pg_logical_slot_get_changes</function> ( <parameter>slot_name</parameter> <type>name</type>, <parameter>upto_lsn</parameter> <type>pg_lsn</type>, <parameter>upto_nchanges</parameter> <type>integer</type>, <literal>VARIADIC</literal> <parameter>options</parameter> <type>text[]</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>lsn</parameter> <type>pg_lsn</type>,
|
|
<parameter>xid</parameter> <type>xid</type>,
|
|
<parameter>data</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Returns changes in the slot <parameter>slot_name</parameter>, starting
|
|
from the point from which changes have been consumed last. If
|
|
<parameter>upto_lsn</parameter>
|
|
and <parameter>upto_nchanges</parameter> are NULL,
|
|
logical decoding will continue until end of WAL. If
|
|
<parameter>upto_lsn</parameter> is non-NULL, decoding will include only
|
|
those transactions which commit prior to the specified LSN. If
|
|
<parameter>upto_nchanges</parameter> is non-NULL, decoding will
|
|
stop when the number of rows produced by decoding exceeds
|
|
the specified value. Note, however, that the actual number of
|
|
rows returned may be larger, since this limit is only checked after
|
|
adding the rows produced when decoding each new transaction commit.
|
|
If the specified slot is a logical failover slot then the function will
|
|
not return until all physical slots specified in
|
|
<link linkend="guc-standby-slot-names"><varname>standby_slot_names</varname></link>
|
|
have confirmed WAL receipt.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-logical-slot-peek-changes" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_logical_slot_peek_changes</primary>
|
|
</indexterm>
|
|
<function>pg_logical_slot_peek_changes</function> ( <parameter>slot_name</parameter> <type>name</type>, <parameter>upto_lsn</parameter> <type>pg_lsn</type>, <parameter>upto_nchanges</parameter> <type>integer</type>, <literal>VARIADIC</literal> <parameter>options</parameter> <type>text[]</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>lsn</parameter> <type>pg_lsn</type>,
|
|
<parameter>xid</parameter> <type>xid</type>,
|
|
<parameter>data</parameter> <type>text</type> )
|
|
</para>
|
|
<para>
|
|
Behaves just like
|
|
the <function>pg_logical_slot_get_changes()</function> function,
|
|
except that changes are not consumed; that is, they will be returned
|
|
again on future calls.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_logical_slot_get_binary_changes</primary>
|
|
</indexterm>
|
|
<function>pg_logical_slot_get_binary_changes</function> ( <parameter>slot_name</parameter> <type>name</type>, <parameter>upto_lsn</parameter> <type>pg_lsn</type>, <parameter>upto_nchanges</parameter> <type>integer</type>, <literal>VARIADIC</literal> <parameter>options</parameter> <type>text[]</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>lsn</parameter> <type>pg_lsn</type>,
|
|
<parameter>xid</parameter> <type>xid</type>,
|
|
<parameter>data</parameter> <type>bytea</type> )
|
|
</para>
|
|
<para>
|
|
Behaves just like
|
|
the <function>pg_logical_slot_get_changes()</function> function,
|
|
except that changes are returned as <type>bytea</type>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_logical_slot_peek_binary_changes</primary>
|
|
</indexterm>
|
|
<function>pg_logical_slot_peek_binary_changes</function> ( <parameter>slot_name</parameter> <type>name</type>, <parameter>upto_lsn</parameter> <type>pg_lsn</type>, <parameter>upto_nchanges</parameter> <type>integer</type>, <literal>VARIADIC</literal> <parameter>options</parameter> <type>text[]</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>lsn</parameter> <type>pg_lsn</type>,
|
|
<parameter>xid</parameter> <type>xid</type>,
|
|
<parameter>data</parameter> <type>bytea</type> )
|
|
</para>
|
|
<para>
|
|
Behaves just like
|
|
the <function>pg_logical_slot_peek_changes()</function> function,
|
|
except that changes are returned as <type>bytea</type>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-replication-slot-advance" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_slot_advance</primary>
|
|
</indexterm>
|
|
<function>pg_replication_slot_advance</function> ( <parameter>slot_name</parameter> <type>name</type>, <parameter>upto_lsn</parameter> <type>pg_lsn</type> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>slot_name</parameter> <type>name</type>,
|
|
<parameter>end_lsn</parameter> <type>pg_lsn</type> )
|
|
</para>
|
|
<para>
|
|
Advances the current confirmed position of a replication slot named
|
|
<parameter>slot_name</parameter>. The slot will not be moved backwards,
|
|
and it will not be moved beyond the current insert location. Returns
|
|
the name of the slot and the actual position that it was advanced to.
|
|
The updated slot position information is written out at the next
|
|
checkpoint if any advancing is done. So in the event of a crash, the
|
|
slot may return to an earlier position. If the specified slot is a
|
|
logical failover slot then the function will not return until all
|
|
physical slots specified in
|
|
<link linkend="guc-standby-slot-names"><varname>standby_slot_names</varname></link>
|
|
have confirmed WAL receipt.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-replication-origin-create" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_create</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_create</function> ( <parameter>node_name</parameter> <type>text</type> )
|
|
<returnvalue>oid</returnvalue>
|
|
</para>
|
|
<para>
|
|
Creates a replication origin with the given external
|
|
name, and returns the internal ID assigned to it.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-replication-origin-drop" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_drop</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_drop</function> ( <parameter>node_name</parameter> <type>text</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Deletes a previously-created replication origin, including any
|
|
associated replay progress.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_oid</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_oid</function> ( <parameter>node_name</parameter> <type>text</type> )
|
|
<returnvalue>oid</returnvalue>
|
|
</para>
|
|
<para>
|
|
Looks up a replication origin by name and returns the internal ID. If
|
|
no such replication origin is found, <literal>NULL</literal> is
|
|
returned.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-replication-origin-session-setup" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_session_setup</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_session_setup</function> ( <parameter>node_name</parameter> <type>text</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Marks the current session as replaying from the given
|
|
origin, allowing replay progress to be tracked.
|
|
Can only be used if no origin is currently selected.
|
|
Use <function>pg_replication_origin_session_reset</function> to undo.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_session_reset</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_session_reset</function> ()
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cancels the effects
|
|
of <function>pg_replication_origin_session_setup()</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_session_is_setup</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_session_is_setup</function> ()
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns true if a replication origin has been selected in the
|
|
current session.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-replication-origin-session-progress" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_session_progress</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_session_progress</function> ( <parameter>flush</parameter> <type>boolean</type> )
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the replay location for the replication origin selected in
|
|
the current session. The parameter <parameter>flush</parameter>
|
|
determines whether the corresponding local transaction will be
|
|
guaranteed to have been flushed to disk or not.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-replication-origin-xact-setup" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_xact_setup</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_xact_setup</function> ( <parameter>origin_lsn</parameter> <type>pg_lsn</type>, <parameter>origin_timestamp</parameter> <type>timestamp with time zone</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Marks the current transaction as replaying a transaction that has
|
|
committed at the given <acronym>LSN</acronym> and timestamp. Can
|
|
only be called when a replication origin has been selected
|
|
using <function>pg_replication_origin_session_setup</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-replication-origin-xact-reset" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_xact_reset</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_xact_reset</function> ()
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cancels the effects of
|
|
<function>pg_replication_origin_xact_setup()</function>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-replication-origin-advance" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_advance</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_advance</function> ( <parameter>node_name</parameter> <type>text</type>, <parameter>lsn</parameter> <type>pg_lsn</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Sets replication progress for the given node to the given
|
|
location. This is primarily useful for setting up the initial
|
|
location, or setting a new location after configuration changes and
|
|
similar. Be aware that careless use of this function can lead to
|
|
inconsistently replicated data.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-replication-origin-progress" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_replication_origin_progress</primary>
|
|
</indexterm>
|
|
<function>pg_replication_origin_progress</function> ( <parameter>node_name</parameter> <type>text</type>, <parameter>flush</parameter> <type>boolean</type> )
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the replay location for the given replication origin. The
|
|
parameter <parameter>flush</parameter> determines whether the
|
|
corresponding local transaction will be guaranteed to have been
|
|
flushed to disk or not.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-logical-emit-message" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_logical_emit_message</primary>
|
|
</indexterm>
|
|
<function>pg_logical_emit_message</function> ( <parameter>transactional</parameter> <type>boolean</type>, <parameter>prefix</parameter> <type>text</type>, <parameter>content</parameter> <type>text</type> [, <parameter>flush</parameter> <type>boolean</type> <literal>DEFAULT</literal> <literal>false</literal>] )
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_logical_emit_message</function> ( <parameter>transactional</parameter> <type>boolean</type>, <parameter>prefix</parameter> <type>text</type>, <parameter>content</parameter> <type>bytea</type> [, <parameter>flush</parameter> <type>boolean</type> <literal>DEFAULT</literal> <literal>false</literal>] )
|
|
<returnvalue>pg_lsn</returnvalue>
|
|
</para>
|
|
<para>
|
|
Emits a logical decoding message. This can be used to pass generic
|
|
messages to logical decoding plugins through
|
|
WAL. The <parameter>transactional</parameter> parameter specifies if
|
|
the message should be part of the current transaction, or if it should
|
|
be written immediately and decoded as soon as the logical decoder
|
|
reads the record. The <parameter>prefix</parameter> parameter is a
|
|
textual prefix that can be used by logical decoding plugins to easily
|
|
recognize messages that are interesting for them.
|
|
The <parameter>content</parameter> parameter is the content of the
|
|
message, given either in text or binary form.
|
|
The <parameter>flush</parameter> parameter (default set to
|
|
<literal>false</literal>) controls if the message is immediately
|
|
flushed to WAL or not. <parameter>flush</parameter> has no effect
|
|
with <parameter>transactional</parameter>, as the message's WAL
|
|
record is flushed along with its transaction.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry id="pg-sync-replication-slots" role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_sync_replication_slots</primary>
|
|
</indexterm>
|
|
<function>pg_sync_replication_slots</function> ()
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Synchronize the logical failover replication slots from the primary
|
|
server to the standby server. This function can only be executed on the
|
|
standby server. Temporary synced slots, if any, cannot be used for
|
|
logical decoding and must be dropped after promotion. See
|
|
<xref linkend="logicaldecoding-replication-slots-synchronization"/> for details.
|
|
Note that this function cannot be executed if
|
|
<link linkend="guc-sync-replication-slots"><varname>
|
|
sync_replication_slots</varname></link> is enabled and the slotsync
|
|
worker is already running to perform the synchronization of slots.
|
|
</para>
|
|
|
|
<caution>
|
|
<para>
|
|
If, after executing the function,
|
|
<link linkend="guc-hot-standby-feedback">
|
|
<varname>hot_standby_feedback</varname></link> is disabled on
|
|
the standby or the physical slot configured in
|
|
<link linkend="guc-primary-slot-name">
|
|
<varname>primary_slot_name</varname></link> is
|
|
removed, then it is possible that the necessary rows of the
|
|
synchronized slot will be removed by the VACUUM process on the primary
|
|
server, resulting in the synchronized slot becoming invalidated.
|
|
</para>
|
|
</caution>
|
|
</entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-admin-dbobject">
|
|
<title>Database Object Management Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-admin-dbsize"/> calculate
|
|
the disk space usage of database objects, or assist in presentation
|
|
or understanding of usage results. <literal>bigint</literal> results
|
|
are measured in bytes. If an OID that does
|
|
not represent an existing object is passed to one of these
|
|
functions, <literal>NULL</literal> is returned.
|
|
</para>
|
|
|
|
<table id="functions-admin-dbsize">
|
|
<title>Database Object Size Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_column_size</primary>
|
|
</indexterm>
|
|
<function>pg_column_size</function> ( <type>"any"</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Shows the number of bytes used to store any individual data value. If
|
|
applied directly to a table column value, this reflects any
|
|
compression that was done.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_column_compression</primary>
|
|
</indexterm>
|
|
<function>pg_column_compression</function> ( <type>"any"</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Shows the compression algorithm that was used to compress
|
|
an individual variable-length value. Returns <literal>NULL</literal>
|
|
if the value is not compressed.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_column_toast_chunk_id</primary>
|
|
</indexterm>
|
|
<function>pg_column_toast_chunk_id</function> ( <type>"any"</type> )
|
|
<returnvalue>oid</returnvalue>
|
|
</para>
|
|
<para>
|
|
Shows the <structfield>chunk_id</structfield> of an on-disk
|
|
<acronym>TOAST</acronym>ed value. Returns <literal>NULL</literal>
|
|
if the value is un-<acronym>TOAST</acronym>ed or not on-disk. See
|
|
<xref linkend="storage-toast"/> for more information about
|
|
<acronym>TOAST</acronym>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_database_size</primary>
|
|
</indexterm>
|
|
<function>pg_database_size</function> ( <type>name</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_database_size</function> ( <type>oid</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the total disk space used by the database with the specified
|
|
name or OID. To use this function, you must
|
|
have <literal>CONNECT</literal> privilege on the specified database
|
|
(which is granted by default) or have privileges of
|
|
the <literal>pg_read_all_stats</literal> role.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_indexes_size</primary>
|
|
</indexterm>
|
|
<function>pg_indexes_size</function> ( <type>regclass</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the total disk space used by indexes attached to the
|
|
specified table.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_relation_size</primary>
|
|
</indexterm>
|
|
<function>pg_relation_size</function> ( <parameter>relation</parameter> <type>regclass</type> <optional>, <parameter>fork</parameter> <type>text</type> </optional> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the disk space used by one <quote>fork</quote> of the
|
|
specified relation. (Note that for most purposes it is more
|
|
convenient to use the higher-level
|
|
functions <function>pg_total_relation_size</function>
|
|
or <function>pg_table_size</function>, which sum the sizes of all
|
|
forks.) With one argument, this returns the size of the main data
|
|
fork of the relation. The second argument can be provided to specify
|
|
which fork to examine:
|
|
<itemizedlist spacing="compact">
|
|
<listitem>
|
|
<para>
|
|
<literal>main</literal> returns the size of the main
|
|
data fork of the relation.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>fsm</literal> returns the size of the Free Space Map
|
|
(see <xref linkend="storage-fsm"/>) associated with the relation.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>vm</literal> returns the size of the Visibility Map
|
|
(see <xref linkend="storage-vm"/>) associated with the relation.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>init</literal> returns the size of the initialization
|
|
fork, if any, associated with the relation.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_size_bytes</primary>
|
|
</indexterm>
|
|
<function>pg_size_bytes</function> ( <type>text</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts a size in human-readable format (as returned
|
|
by <function>pg_size_pretty</function>) into bytes. Valid units are
|
|
<literal>bytes</literal>, <literal>B</literal>, <literal>kB</literal>,
|
|
<literal>MB</literal>, <literal>GB</literal>, <literal>TB</literal>,
|
|
and <literal>PB</literal>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_size_pretty</primary>
|
|
</indexterm>
|
|
<function>pg_size_pretty</function> ( <type>bigint</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_size_pretty</function> ( <type>numeric</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Converts a size in bytes into a more easily human-readable format with
|
|
size units (bytes, kB, MB, GB, TB, or PB as appropriate). Note that the
|
|
units are powers of 2 rather than powers of 10, so 1kB is 1024 bytes,
|
|
1MB is 1024<superscript>2</superscript> = 1048576 bytes, and so on.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_table_size</primary>
|
|
</indexterm>
|
|
<function>pg_table_size</function> ( <type>regclass</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the disk space used by the specified table, excluding indexes
|
|
(but including its TOAST table if any, free space map, and visibility
|
|
map).
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_tablespace_size</primary>
|
|
</indexterm>
|
|
<function>pg_tablespace_size</function> ( <type>name</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_tablespace_size</function> ( <type>oid</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the total disk space used in the tablespace with the
|
|
specified name or OID. To use this function, you must
|
|
have <literal>CREATE</literal> privilege on the specified tablespace
|
|
or have privileges of the <literal>pg_read_all_stats</literal> role,
|
|
unless it is the default tablespace for the current database.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_total_relation_size</primary>
|
|
</indexterm>
|
|
<function>pg_total_relation_size</function> ( <type>regclass</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the total disk space used by the specified table, including
|
|
all indexes and <acronym>TOAST</acronym> data. The result is
|
|
equivalent to <function>pg_table_size</function>
|
|
<literal>+</literal> <function>pg_indexes_size</function>.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The functions above that operate on tables or indexes accept a
|
|
<type>regclass</type> argument, which is simply the OID of the table or index
|
|
in the <structname>pg_class</structname> system catalog. You do not have to look up
|
|
the OID by hand, however, since the <type>regclass</type> data type's input
|
|
converter will do the work for you. See <xref linkend="datatype-oid"/>
|
|
for details.
|
|
</para>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-admin-dblocation"/> assist
|
|
in identifying the specific disk files associated with database objects.
|
|
</para>
|
|
|
|
<table id="functions-admin-dblocation">
|
|
<title>Database Object Location Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_relation_filenode</primary>
|
|
</indexterm>
|
|
<function>pg_relation_filenode</function> ( <parameter>relation</parameter> <type>regclass</type> )
|
|
<returnvalue>oid</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the <quote>filenode</quote> number currently assigned to the
|
|
specified relation. The filenode is the base component of the file
|
|
name(s) used for the relation (see
|
|
<xref linkend="storage-file-layout"/> for more information).
|
|
For most relations the result is the same as
|
|
<structname>pg_class</structname>.<structfield>relfilenode</structfield>,
|
|
but for certain system catalogs <structfield>relfilenode</structfield>
|
|
is zero and this function must be used to get the correct value. The
|
|
function returns NULL if passed a relation that does not have storage,
|
|
such as a view.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_relation_filepath</primary>
|
|
</indexterm>
|
|
<function>pg_relation_filepath</function> ( <parameter>relation</parameter> <type>regclass</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the entire file path name (relative to the database cluster's
|
|
data directory, <varname>PGDATA</varname>) of the relation.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_filenode_relation</primary>
|
|
</indexterm>
|
|
<function>pg_filenode_relation</function> ( <parameter>tablespace</parameter> <type>oid</type>, <parameter>filenode</parameter> <type>oid</type> )
|
|
<returnvalue>regclass</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a relation's OID given the tablespace OID and filenode it is
|
|
stored under. This is essentially the inverse mapping of
|
|
<function>pg_relation_filepath</function>. For a relation in the
|
|
database's default tablespace, the tablespace can be specified as zero.
|
|
Returns <literal>NULL</literal> if no relation in the current database
|
|
is associated with the given values.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-admin-collation"/> lists functions used to manage
|
|
collations.
|
|
</para>
|
|
|
|
<table id="functions-admin-collation">
|
|
<title>Collation Management Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_collation_actual_version</primary>
|
|
</indexterm>
|
|
<function>pg_collation_actual_version</function> ( <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the actual version of the collation object as it is currently
|
|
installed in the operating system. If this is different from the
|
|
value in
|
|
<structname>pg_collation</structname>.<structfield>collversion</structfield>,
|
|
then objects depending on the collation might need to be rebuilt. See
|
|
also <xref linkend="sql-altercollation"/>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_database_collation_actual_version</primary>
|
|
</indexterm>
|
|
<function>pg_database_collation_actual_version</function> ( <type>oid</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the actual version of the database's collation as it is currently
|
|
installed in the operating system. If this is different from the
|
|
value in
|
|
<structname>pg_database</structname>.<structfield>datcollversion</structfield>,
|
|
then objects depending on the collation might need to be rebuilt. See
|
|
also <xref linkend="sql-alterdatabase"/>.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_import_system_collations</primary>
|
|
</indexterm>
|
|
<function>pg_import_system_collations</function> ( <parameter>schema</parameter> <type>regnamespace</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Adds collations to the system
|
|
catalog <structname>pg_collation</structname> based on all the locales
|
|
it finds in the operating system. This is
|
|
what <command>initdb</command> uses; see
|
|
<xref linkend="collation-managing"/> for more details. If additional
|
|
locales are installed into the operating system later on, this
|
|
function can be run again to add collations for the new locales.
|
|
Locales that match existing entries
|
|
in <structname>pg_collation</structname> will be skipped. (But
|
|
collation objects based on locales that are no longer present in the
|
|
operating system are not removed by this function.)
|
|
The <parameter>schema</parameter> parameter would typically
|
|
be <literal>pg_catalog</literal>, but that is not a requirement; the
|
|
collations could be installed into some other schema as well. The
|
|
function returns the number of new collation objects it created.
|
|
Use of this function is restricted to superusers.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-info-partition"/> lists functions that provide
|
|
information about the structure of partitioned tables.
|
|
</para>
|
|
|
|
<table id="functions-info-partition">
|
|
<title>Partitioning Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_partition_tree</primary>
|
|
</indexterm>
|
|
<function>pg_partition_tree</function> ( <type>regclass</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>relid</parameter> <type>regclass</type>,
|
|
<parameter>parentrelid</parameter> <type>regclass</type>,
|
|
<parameter>isleaf</parameter> <type>boolean</type>,
|
|
<parameter>level</parameter> <type>integer</type> )
|
|
</para>
|
|
<para>
|
|
Lists the tables or indexes in the partition tree of the
|
|
given partitioned table or partitioned index, with one row for each
|
|
partition. Information provided includes the OID of the partition,
|
|
the OID of its immediate parent, a boolean value telling if the
|
|
partition is a leaf, and an integer telling its level in the hierarchy.
|
|
The level value is 0 for the input table or index, 1 for its
|
|
immediate child partitions, 2 for their partitions, and so on.
|
|
Returns no rows if the relation does not exist or is not a partition
|
|
or partitioned table.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_partition_ancestors</primary>
|
|
</indexterm>
|
|
<function>pg_partition_ancestors</function> ( <type>regclass</type> )
|
|
<returnvalue>setof regclass</returnvalue>
|
|
</para>
|
|
<para>
|
|
Lists the ancestor relations of the given partition,
|
|
including the relation itself. Returns no rows if the relation
|
|
does not exist or is not a partition or partitioned table.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_partition_root</primary>
|
|
</indexterm>
|
|
<function>pg_partition_root</function> ( <type>regclass</type> )
|
|
<returnvalue>regclass</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the top-most parent of the partition tree to which the given
|
|
relation belongs. Returns <literal>NULL</literal> if the relation
|
|
does not exist or is not a partition or partitioned table.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
For example, to check the total size of the data contained in a
|
|
partitioned table <structname>measurement</structname>, one could use the
|
|
following query:
|
|
<programlisting>
|
|
SELECT pg_size_pretty(sum(pg_relation_size(relid))) AS total_size
|
|
FROM pg_partition_tree('measurement');
|
|
</programlisting>
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-admin-index">
|
|
<title>Index Maintenance Functions</title>
|
|
|
|
<para>
|
|
<xref linkend="functions-admin-index-table"/> shows the functions
|
|
available for index maintenance tasks. (Note that these maintenance
|
|
tasks are normally done automatically by autovacuum; use of these
|
|
functions is only required in special cases.)
|
|
These functions cannot be executed during recovery.
|
|
Use of these functions is restricted to superusers and the owner
|
|
of the given index.
|
|
</para>
|
|
|
|
<table id="functions-admin-index-table">
|
|
<title>Index Maintenance Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>brin_summarize_new_values</primary>
|
|
</indexterm>
|
|
<function>brin_summarize_new_values</function> ( <parameter>index</parameter> <type>regclass</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Scans the specified BRIN index to find page ranges in the base table
|
|
that are not currently summarized by the index; for any such range it
|
|
creates a new summary index tuple by scanning those table pages.
|
|
Returns the number of new page range summaries that were inserted
|
|
into the index.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>brin_summarize_range</primary>
|
|
</indexterm>
|
|
<function>brin_summarize_range</function> ( <parameter>index</parameter> <type>regclass</type>, <parameter>blockNumber</parameter> <type>bigint</type> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Summarizes the page range covering the given block, if not already
|
|
summarized. This is
|
|
like <function>brin_summarize_new_values</function> except that it
|
|
only processes the page range that covers the given table block number.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>brin_desummarize_range</primary>
|
|
</indexterm>
|
|
<function>brin_desummarize_range</function> ( <parameter>index</parameter> <type>regclass</type>, <parameter>blockNumber</parameter> <type>bigint</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Removes the BRIN index tuple that summarizes the page range covering
|
|
the given table block, if there is one.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>gin_clean_pending_list</primary>
|
|
</indexterm>
|
|
<function>gin_clean_pending_list</function> ( <parameter>index</parameter> <type>regclass</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Cleans up the <quote>pending</quote> list of the specified GIN index
|
|
by moving entries in it, in bulk, to the main GIN data structure.
|
|
Returns the number of pages removed from the pending list.
|
|
If the argument is a GIN index built with
|
|
the <literal>fastupdate</literal> option disabled, no cleanup happens
|
|
and the result is zero, because the index doesn't have a pending list.
|
|
See <xref linkend="gin-fast-update"/> and <xref linkend="gin-tips"/>
|
|
for details about the pending list and <literal>fastupdate</literal>
|
|
option.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-admin-genfile">
|
|
<title>Generic File Access Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref
|
|
linkend="functions-admin-genfile-table"/> provide native access to
|
|
files on the machine hosting the server. Only files within the
|
|
database cluster directory and the <varname>log_directory</varname> can be
|
|
accessed, unless the user is a superuser or is granted the role
|
|
<literal>pg_read_server_files</literal>. Use a relative path for files in
|
|
the cluster directory, and a path matching the <varname>log_directory</varname>
|
|
configuration setting for log files.
|
|
</para>
|
|
|
|
<para>
|
|
Note that granting users the EXECUTE privilege on
|
|
<function>pg_read_file()</function>, or related functions, allows them the
|
|
ability to read any file on the server that the database server process can
|
|
read; these functions bypass all in-database privilege checks. This means
|
|
that, for example, a user with such access is able to read the contents of
|
|
the <structname>pg_authid</structname> table where authentication
|
|
information is stored, as well as read any table data in the database.
|
|
Therefore, granting access to these functions should be carefully
|
|
considered.
|
|
</para>
|
|
|
|
<para>
|
|
When granting privilege on these functions, note that the table entries
|
|
showing optional parameters are mostly implemented as several physical
|
|
functions with different parameter lists. Privilege must be granted
|
|
separately on each such function, if it is to be
|
|
used. <application>psql</application>'s <command>\df</command> command
|
|
can be useful to check what the actual function signatures are.
|
|
</para>
|
|
|
|
<para>
|
|
Some of these functions take an optional <parameter>missing_ok</parameter>
|
|
parameter, which specifies the behavior when the file or directory does
|
|
not exist. If <literal>true</literal>, the function
|
|
returns <literal>NULL</literal> or an empty result set, as appropriate.
|
|
If <literal>false</literal>, an error is raised. (Failure conditions
|
|
other than <quote>file not found</quote> are reported as errors in any
|
|
case.) The default is <literal>false</literal>.
|
|
</para>
|
|
|
|
<table id="functions-admin-genfile-table">
|
|
<title>Generic File Access Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ls_dir</primary>
|
|
</indexterm>
|
|
<function>pg_ls_dir</function> ( <parameter>dirname</parameter> <type>text</type> <optional>, <parameter>missing_ok</parameter> <type>boolean</type>, <parameter>include_dot_dirs</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>setof text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the names of all files (and directories and other special
|
|
files) in the specified
|
|
directory. The <parameter>include_dot_dirs</parameter> parameter
|
|
indicates whether <quote>.</quote> and <quote>..</quote> are to be
|
|
included in the result set; the default is to exclude them. Including
|
|
them can be useful when <parameter>missing_ok</parameter>
|
|
is <literal>true</literal>, to distinguish an empty directory from a
|
|
non-existent directory.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ls_logdir</primary>
|
|
</indexterm>
|
|
<function>pg_ls_logdir</function> ()
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>name</parameter> <type>text</type>,
|
|
<parameter>size</parameter> <type>bigint</type>,
|
|
<parameter>modification</parameter> <type>timestamp with time zone</type> )
|
|
</para>
|
|
<para>
|
|
Returns the name, size, and last modification time (mtime) of each
|
|
ordinary file in the server's log directory. Filenames beginning with
|
|
a dot, directories, and other special files are excluded.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers and roles with privileges of
|
|
the <literal>pg_monitor</literal> role by default, but other users can
|
|
be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ls_waldir</primary>
|
|
</indexterm>
|
|
<function>pg_ls_waldir</function> ()
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>name</parameter> <type>text</type>,
|
|
<parameter>size</parameter> <type>bigint</type>,
|
|
<parameter>modification</parameter> <type>timestamp with time zone</type> )
|
|
</para>
|
|
<para>
|
|
Returns the name, size, and last modification time (mtime) of each
|
|
ordinary file in the server's write-ahead log (WAL) directory.
|
|
Filenames beginning with a dot, directories, and other special files
|
|
are excluded.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers and roles with privileges of
|
|
the <literal>pg_monitor</literal> role by default, but other users can
|
|
be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ls_logicalmapdir</primary>
|
|
</indexterm>
|
|
<function>pg_ls_logicalmapdir</function> ()
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>name</parameter> <type>text</type>,
|
|
<parameter>size</parameter> <type>bigint</type>,
|
|
<parameter>modification</parameter> <type>timestamp with time zone</type> )
|
|
</para>
|
|
<para>
|
|
Returns the name, size, and last modification time (mtime) of each
|
|
ordinary file in the server's <filename>pg_logical/mappings</filename>
|
|
directory. Filenames beginning with a dot, directories, and other
|
|
special files are excluded.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers and members of
|
|
the <literal>pg_monitor</literal> role by default, but other users can
|
|
be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ls_logicalsnapdir</primary>
|
|
</indexterm>
|
|
<function>pg_ls_logicalsnapdir</function> ()
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>name</parameter> <type>text</type>,
|
|
<parameter>size</parameter> <type>bigint</type>,
|
|
<parameter>modification</parameter> <type>timestamp with time zone</type> )
|
|
</para>
|
|
<para>
|
|
Returns the name, size, and last modification time (mtime) of each
|
|
ordinary file in the server's <filename>pg_logical/snapshots</filename>
|
|
directory. Filenames beginning with a dot, directories, and other
|
|
special files are excluded.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers and members of
|
|
the <literal>pg_monitor</literal> role by default, but other users can
|
|
be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ls_replslotdir</primary>
|
|
</indexterm>
|
|
<function>pg_ls_replslotdir</function> ( <parameter>slot_name</parameter> <type>text</type> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>name</parameter> <type>text</type>,
|
|
<parameter>size</parameter> <type>bigint</type>,
|
|
<parameter>modification</parameter> <type>timestamp with time zone</type> )
|
|
</para>
|
|
<para>
|
|
Returns the name, size, and last modification time (mtime) of each
|
|
ordinary file in the server's <filename>pg_replslot/slot_name</filename>
|
|
directory, where <parameter>slot_name</parameter> is the name of the
|
|
replication slot provided as input of the function. Filenames beginning
|
|
with a dot, directories, and other special files are excluded.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers and members of
|
|
the <literal>pg_monitor</literal> role by default, but other users can
|
|
be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_ls_archive_statusdir</primary>
|
|
</indexterm>
|
|
<function>pg_ls_archive_statusdir</function> ()
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>name</parameter> <type>text</type>,
|
|
<parameter>size</parameter> <type>bigint</type>,
|
|
<parameter>modification</parameter> <type>timestamp with time zone</type> )
|
|
</para>
|
|
<para>
|
|
Returns the name, size, and last modification time (mtime) of each
|
|
ordinary file in the server's WAL archive status directory
|
|
(<filename>pg_wal/archive_status</filename>). Filenames beginning
|
|
with a dot, directories, and other special files are excluded.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers and members of
|
|
the <literal>pg_monitor</literal> role by default, but other users can
|
|
be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
|
|
<indexterm>
|
|
<primary>pg_ls_tmpdir</primary>
|
|
</indexterm>
|
|
<function>pg_ls_tmpdir</function> ( <optional> <parameter>tablespace</parameter> <type>oid</type> </optional> )
|
|
<returnvalue>setof record</returnvalue>
|
|
( <parameter>name</parameter> <type>text</type>,
|
|
<parameter>size</parameter> <type>bigint</type>,
|
|
<parameter>modification</parameter> <type>timestamp with time zone</type> )
|
|
</para>
|
|
<para>
|
|
Returns the name, size, and last modification time (mtime) of each
|
|
ordinary file in the temporary file directory for the
|
|
specified <parameter>tablespace</parameter>.
|
|
If <parameter>tablespace</parameter> is not provided,
|
|
the <literal>pg_default</literal> tablespace is examined. Filenames
|
|
beginning with a dot, directories, and other special files are
|
|
excluded.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers and members of
|
|
the <literal>pg_monitor</literal> role by default, but other users can
|
|
be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_read_file</primary>
|
|
</indexterm>
|
|
<function>pg_read_file</function> ( <parameter>filename</parameter> <type>text</type> <optional>, <parameter>offset</parameter> <type>bigint</type>, <parameter>length</parameter> <type>bigint</type> </optional> <optional>, <parameter>missing_ok</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns all or part of a text file, starting at the
|
|
given byte <parameter>offset</parameter>, returning at
|
|
most <parameter>length</parameter> bytes (less if the end of file is
|
|
reached first). If <parameter>offset</parameter> is negative, it is
|
|
relative to the end of the file. If <parameter>offset</parameter>
|
|
and <parameter>length</parameter> are omitted, the entire file is
|
|
returned. The bytes read from the file are interpreted as a string in
|
|
the database's encoding; an error is thrown if they are not valid in
|
|
that encoding.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_read_binary_file</primary>
|
|
</indexterm>
|
|
<function>pg_read_binary_file</function> ( <parameter>filename</parameter> <type>text</type> <optional>, <parameter>offset</parameter> <type>bigint</type>, <parameter>length</parameter> <type>bigint</type> </optional> <optional>, <parameter>missing_ok</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns all or part of a file. This function is identical to
|
|
<function>pg_read_file</function> except that it can read arbitrary
|
|
binary data, returning the result as <type>bytea</type>
|
|
not <type>text</type>; accordingly, no encoding checks are performed.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para>
|
|
<para>
|
|
In combination with the <function>convert_from</function> function,
|
|
this function can be used to read a text file in a specified encoding
|
|
and convert to the database's encoding:
|
|
<programlisting>
|
|
SELECT convert_from(pg_read_binary_file('file_in_utf8.txt'), 'UTF8');
|
|
</programlisting>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_stat_file</primary>
|
|
</indexterm>
|
|
<function>pg_stat_file</function> ( <parameter>filename</parameter> <type>text</type> <optional>, <parameter>missing_ok</parameter> <type>boolean</type> </optional> )
|
|
<returnvalue>record</returnvalue>
|
|
( <parameter>size</parameter> <type>bigint</type>,
|
|
<parameter>access</parameter> <type>timestamp with time zone</type>,
|
|
<parameter>modification</parameter> <type>timestamp with time zone</type>,
|
|
<parameter>change</parameter> <type>timestamp with time zone</type>,
|
|
<parameter>creation</parameter> <type>timestamp with time zone</type>,
|
|
<parameter>isdir</parameter> <type>boolean</type> )
|
|
</para>
|
|
<para>
|
|
Returns a record containing the file's size, last access time stamp,
|
|
last modification time stamp, last file status change time stamp (Unix
|
|
platforms only), file creation time stamp (Windows only), and a flag
|
|
indicating if it is a directory.
|
|
</para>
|
|
<para>
|
|
This function is restricted to superusers by default, but other users
|
|
can be granted EXECUTE to run the function.
|
|
</para></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="functions-advisory-locks">
|
|
<title>Advisory Lock Functions</title>
|
|
|
|
<para>
|
|
The functions shown in <xref linkend="functions-advisory-locks-table"/>
|
|
manage advisory locks. For details about proper use of these functions,
|
|
see <xref linkend="advisory-locks"/>.
|
|
</para>
|
|
|
|
<para>
|
|
All these functions are intended to be used to lock application-defined
|
|
resources, which can be identified either by a single 64-bit key value or
|
|
two 32-bit key values (note that these two key spaces do not overlap).
|
|
If another session already holds a conflicting lock on the same resource
|
|
identifier, the functions will either wait until the resource becomes
|
|
available, or return a <literal>false</literal> result, as appropriate for
|
|
the function.
|
|
Locks can be either shared or exclusive: a shared lock does not conflict
|
|
with other shared locks on the same resource, only with exclusive locks.
|
|
Locks can be taken at session level (so that they are held until released
|
|
or the session ends) or at transaction level (so that they are held until
|
|
the current transaction ends; there is no provision for manual release).
|
|
Multiple session-level lock requests stack, so that if the same resource
|
|
identifier is locked three times there must then be three unlock requests
|
|
to release the resource in advance of session end.
|
|
</para>
|
|
|
|
<table id="functions-advisory-locks-table">
|
|
<title>Advisory Lock Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_advisory_lock</primary>
|
|
</indexterm>
|
|
<function>pg_advisory_lock</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_advisory_lock</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Obtains an exclusive session-level advisory lock, waiting if necessary.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_advisory_lock_shared</primary>
|
|
</indexterm>
|
|
<function>pg_advisory_lock_shared</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_advisory_lock_shared</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Obtains a shared session-level advisory lock, waiting if necessary.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_advisory_unlock</primary>
|
|
</indexterm>
|
|
<function>pg_advisory_unlock</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_advisory_unlock</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Releases a previously-acquired exclusive session-level advisory lock.
|
|
Returns <literal>true</literal> if the lock is successfully released.
|
|
If the lock was not held, <literal>false</literal> is returned, and in
|
|
addition, an SQL warning will be reported by the server.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_advisory_unlock_all</primary>
|
|
</indexterm>
|
|
<function>pg_advisory_unlock_all</function> ()
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Releases all session-level advisory locks held by the current session.
|
|
(This function is implicitly invoked at session end, even if the
|
|
client disconnects ungracefully.)
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_advisory_unlock_shared</primary>
|
|
</indexterm>
|
|
<function>pg_advisory_unlock_shared</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_advisory_unlock_shared</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Releases a previously-acquired shared session-level advisory lock.
|
|
Returns <literal>true</literal> if the lock is successfully released.
|
|
If the lock was not held, <literal>false</literal> is returned, and in
|
|
addition, an SQL warning will be reported by the server.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_advisory_xact_lock</primary>
|
|
</indexterm>
|
|
<function>pg_advisory_xact_lock</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_advisory_xact_lock</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Obtains an exclusive transaction-level advisory lock, waiting if
|
|
necessary.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_advisory_xact_lock_shared</primary>
|
|
</indexterm>
|
|
<function>pg_advisory_xact_lock_shared</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_advisory_xact_lock_shared</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>void</returnvalue>
|
|
</para>
|
|
<para>
|
|
Obtains a shared transaction-level advisory lock, waiting if
|
|
necessary.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_try_advisory_lock</primary>
|
|
</indexterm>
|
|
<function>pg_try_advisory_lock</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_try_advisory_lock</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Obtains an exclusive session-level advisory lock if available.
|
|
This will either obtain the lock immediately and
|
|
return <literal>true</literal>, or return <literal>false</literal>
|
|
without waiting if the lock cannot be acquired immediately.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_try_advisory_lock_shared</primary>
|
|
</indexterm>
|
|
<function>pg_try_advisory_lock_shared</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_try_advisory_lock_shared</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Obtains a shared session-level advisory lock if available.
|
|
This will either obtain the lock immediately and
|
|
return <literal>true</literal>, or return <literal>false</literal>
|
|
without waiting if the lock cannot be acquired immediately.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_try_advisory_xact_lock</primary>
|
|
</indexterm>
|
|
<function>pg_try_advisory_xact_lock</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_try_advisory_xact_lock</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Obtains an exclusive transaction-level advisory lock if available.
|
|
This will either obtain the lock immediately and
|
|
return <literal>true</literal>, or return <literal>false</literal>
|
|
without waiting if the lock cannot be acquired immediately.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_try_advisory_xact_lock_shared</primary>
|
|
</indexterm>
|
|
<function>pg_try_advisory_xact_lock_shared</function> ( <parameter>key</parameter> <type>bigint</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>pg_try_advisory_xact_lock_shared</function> ( <parameter>key1</parameter> <type>integer</type>, <parameter>key2</parameter> <type>integer</type> )
|
|
<returnvalue>boolean</returnvalue>
|
|
</para>
|
|
<para>
|
|
Obtains a shared transaction-level advisory lock if available.
|
|
This will either obtain the lock immediately and
|
|
return <literal>true</literal>, or return <literal>false</literal>
|
|
without waiting if the lock cannot be acquired immediately.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="functions-trigger">
|
|
<title>Trigger Functions</title>
|
|
|
|
<para>
|
|
While many uses of triggers involve user-written trigger functions,
|
|
<productname>PostgreSQL</productname> provides a few built-in trigger
|
|
functions that can be used directly in user-defined triggers. These
|
|
are summarized in <xref linkend="builtin-triggers-table"/>.
|
|
(Additional built-in trigger functions exist, which implement foreign
|
|
key constraints and deferred index constraints. Those are not documented
|
|
here since users need not use them directly.)
|
|
</para>
|
|
|
|
<para>
|
|
For more information about creating triggers, see
|
|
<xref linkend="sql-createtrigger"/>.
|
|
</para>
|
|
|
|
<table id="builtin-triggers-table">
|
|
<title>Built-In Trigger Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para>
|
|
<para>
|
|
Example Usage
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>suppress_redundant_updates_trigger</primary>
|
|
</indexterm>
|
|
<function>suppress_redundant_updates_trigger</function> ( )
|
|
<returnvalue>trigger</returnvalue>
|
|
</para>
|
|
<para>
|
|
Suppresses do-nothing update operations. See below for details.
|
|
</para>
|
|
<para>
|
|
<literal>CREATE TRIGGER ... suppress_redundant_updates_trigger()</literal>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>tsvector_update_trigger</primary>
|
|
</indexterm>
|
|
<function>tsvector_update_trigger</function> ( )
|
|
<returnvalue>trigger</returnvalue>
|
|
</para>
|
|
<para>
|
|
Automatically updates a <type>tsvector</type> column from associated
|
|
plain-text document column(s). The text search configuration to use
|
|
is specified by name as a trigger argument. See
|
|
<xref linkend="textsearch-update-triggers"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>CREATE TRIGGER ... tsvector_update_trigger(tsvcol, 'pg_catalog.swedish', title, body)</literal>
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>tsvector_update_trigger_column</primary>
|
|
</indexterm>
|
|
<function>tsvector_update_trigger_column</function> ( )
|
|
<returnvalue>trigger</returnvalue>
|
|
</para>
|
|
<para>
|
|
Automatically updates a <type>tsvector</type> column from associated
|
|
plain-text document column(s). The text search configuration to use
|
|
is taken from a <type>regconfig</type> column of the table. See
|
|
<xref linkend="textsearch-update-triggers"/> for details.
|
|
</para>
|
|
<para>
|
|
<literal>CREATE TRIGGER ... tsvector_update_trigger_column(tsvcol, tsconfigcol, title, body)</literal>
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The <function>suppress_redundant_updates_trigger</function> function,
|
|
when applied as a row-level <literal>BEFORE UPDATE</literal> trigger,
|
|
will prevent any update that does not actually change the data in the
|
|
row from taking place. This overrides the normal behavior which always
|
|
performs a physical row update
|
|
regardless of whether or not the data has changed. (This normal behavior
|
|
makes updates run faster, since no checking is required, and is also
|
|
useful in certain cases.)
|
|
</para>
|
|
|
|
<para>
|
|
Ideally, you should avoid running updates that don't actually
|
|
change the data in the record. Redundant updates can cost considerable
|
|
unnecessary time, especially if there are lots of indexes to alter,
|
|
and space in dead rows that will eventually have to be vacuumed.
|
|
However, detecting such situations in client code is not
|
|
always easy, or even possible, and writing expressions to detect
|
|
them can be error-prone. An alternative is to use
|
|
<function>suppress_redundant_updates_trigger</function>, which will skip
|
|
updates that don't change the data. You should use this with care,
|
|
however. The trigger takes a small but non-trivial time for each record,
|
|
so if most of the records affected by updates do actually change,
|
|
use of this trigger will make updates run slower on average.
|
|
</para>
|
|
|
|
<para>
|
|
The <function>suppress_redundant_updates_trigger</function> function can be
|
|
added to a table like this:
|
|
<programlisting>
|
|
CREATE TRIGGER z_min_update
|
|
BEFORE UPDATE ON tablename
|
|
FOR EACH ROW EXECUTE FUNCTION suppress_redundant_updates_trigger();
|
|
</programlisting>
|
|
In most cases, you need to fire this trigger last for each row, so that
|
|
it does not override other triggers that might wish to alter the row.
|
|
Bearing in mind that triggers fire in name order, you would therefore
|
|
choose a trigger name that comes after the name of any other trigger
|
|
you might have on the table. (Hence the <quote>z</quote> prefix in the
|
|
example.)
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-event-triggers">
|
|
<title>Event Trigger Functions</title>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> provides these helper functions
|
|
to retrieve information from event triggers.
|
|
</para>
|
|
|
|
<para>
|
|
For more information about event triggers,
|
|
see <xref linkend="event-triggers"/>.
|
|
</para>
|
|
|
|
<sect2 id="pg-event-trigger-ddl-command-end-functions">
|
|
<title>Capturing Changes at Command End</title>
|
|
|
|
<indexterm>
|
|
<primary>pg_event_trigger_ddl_commands</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>pg_event_trigger_ddl_commands</function> () <returnvalue>setof record</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
<function>pg_event_trigger_ddl_commands</function> returns a list of
|
|
<acronym>DDL</acronym> commands executed by each user action,
|
|
when invoked in a function attached to a
|
|
<literal>ddl_command_end</literal> event trigger. If called in any other
|
|
context, an error is raised.
|
|
<function>pg_event_trigger_ddl_commands</function> returns one row for each
|
|
base command executed; some commands that are a single SQL sentence
|
|
may return more than one row. This function returns the following
|
|
columns:
|
|
|
|
<informaltable>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Type</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>classid</literal></entry>
|
|
<entry><type>oid</type></entry>
|
|
<entry>OID of catalog the object belongs in</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>objid</literal></entry>
|
|
<entry><type>oid</type></entry>
|
|
<entry>OID of the object itself</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>objsubid</literal></entry>
|
|
<entry><type>integer</type></entry>
|
|
<entry>Sub-object ID (e.g., attribute number for a column)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>command_tag</literal></entry>
|
|
<entry><type>text</type></entry>
|
|
<entry>Command tag</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>object_type</literal></entry>
|
|
<entry><type>text</type></entry>
|
|
<entry>Type of the object</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>schema_name</literal></entry>
|
|
<entry><type>text</type></entry>
|
|
<entry>
|
|
Name of the schema the object belongs in, if any; otherwise <literal>NULL</literal>.
|
|
No quoting is applied.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>object_identity</literal></entry>
|
|
<entry><type>text</type></entry>
|
|
<entry>
|
|
Text rendering of the object identity, schema-qualified. Each
|
|
identifier included in the identity is quoted if necessary.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>in_extension</literal></entry>
|
|
<entry><type>boolean</type></entry>
|
|
<entry>True if the command is part of an extension script</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>command</literal></entry>
|
|
<entry><type>pg_ddl_command</type></entry>
|
|
<entry>
|
|
A complete representation of the command, in internal format.
|
|
This cannot be output directly, but it can be passed to other
|
|
functions to obtain different pieces of information about the
|
|
command.
|
|
</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="pg-event-trigger-sql-drop-functions">
|
|
<title>Processing Objects Dropped by a DDL Command</title>
|
|
|
|
<indexterm>
|
|
<primary>pg_event_trigger_dropped_objects</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>pg_event_trigger_dropped_objects</function> () <returnvalue>setof record</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
<function>pg_event_trigger_dropped_objects</function> returns a list of all objects
|
|
dropped by the command in whose <literal>sql_drop</literal> event it is called.
|
|
If called in any other context, an error is raised.
|
|
This function returns the following columns:
|
|
|
|
<informaltable>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Type</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>classid</literal></entry>
|
|
<entry><type>oid</type></entry>
|
|
<entry>OID of catalog the object belonged in</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>objid</literal></entry>
|
|
<entry><type>oid</type></entry>
|
|
<entry>OID of the object itself</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>objsubid</literal></entry>
|
|
<entry><type>integer</type></entry>
|
|
<entry>Sub-object ID (e.g., attribute number for a column)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>original</literal></entry>
|
|
<entry><type>boolean</type></entry>
|
|
<entry>True if this was one of the root object(s) of the deletion</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>normal</literal></entry>
|
|
<entry><type>boolean</type></entry>
|
|
<entry>
|
|
True if there was a normal dependency relationship
|
|
in the dependency graph leading to this object
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>is_temporary</literal></entry>
|
|
<entry><type>boolean</type></entry>
|
|
<entry>
|
|
True if this was a temporary object
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>object_type</literal></entry>
|
|
<entry><type>text</type></entry>
|
|
<entry>Type of the object</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>schema_name</literal></entry>
|
|
<entry><type>text</type></entry>
|
|
<entry>
|
|
Name of the schema the object belonged in, if any; otherwise <literal>NULL</literal>.
|
|
No quoting is applied.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>object_name</literal></entry>
|
|
<entry><type>text</type></entry>
|
|
<entry>
|
|
Name of the object, if the combination of schema and name can be
|
|
used as a unique identifier for the object; otherwise <literal>NULL</literal>.
|
|
No quoting is applied, and name is never schema-qualified.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>object_identity</literal></entry>
|
|
<entry><type>text</type></entry>
|
|
<entry>
|
|
Text rendering of the object identity, schema-qualified. Each
|
|
identifier included in the identity is quoted if necessary.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>address_names</literal></entry>
|
|
<entry><type>text[]</type></entry>
|
|
<entry>
|
|
An array that, together with <literal>object_type</literal> and
|
|
<literal>address_args</literal>, can be used by
|
|
the <function>pg_get_object_address</function> function to
|
|
recreate the object address in a remote server containing an
|
|
identically named object of the same kind.
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>address_args</literal></entry>
|
|
<entry><type>text[]</type></entry>
|
|
<entry>
|
|
Complement for <literal>address_names</literal>
|
|
</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
</para>
|
|
|
|
<para>
|
|
The <function>pg_event_trigger_dropped_objects</function> function can be used
|
|
in an event trigger like this:
|
|
<programlisting>
|
|
CREATE FUNCTION test_event_trigger_for_drops()
|
|
RETURNS event_trigger LANGUAGE plpgsql AS $$
|
|
DECLARE
|
|
obj record;
|
|
BEGIN
|
|
FOR obj IN SELECT * FROM pg_event_trigger_dropped_objects()
|
|
LOOP
|
|
RAISE NOTICE '% dropped object: % %.% %',
|
|
tg_tag,
|
|
obj.object_type,
|
|
obj.schema_name,
|
|
obj.object_name,
|
|
obj.object_identity;
|
|
END LOOP;
|
|
END;
|
|
$$;
|
|
CREATE EVENT TRIGGER test_event_trigger_for_drops
|
|
ON sql_drop
|
|
EXECUTE FUNCTION test_event_trigger_for_drops();
|
|
</programlisting>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="pg-event-trigger-table-rewrite-functions">
|
|
<title>Handling a Table Rewrite Event</title>
|
|
|
|
<para>
|
|
The functions shown in
|
|
<xref linkend="functions-event-trigger-table-rewrite"/>
|
|
provide information about a table for which a
|
|
<literal>table_rewrite</literal> event has just been called.
|
|
If called in any other context, an error is raised.
|
|
</para>
|
|
|
|
<table id="functions-event-trigger-table-rewrite">
|
|
<title>Table Rewrite Information Functions</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_event_trigger_table_rewrite_oid</primary>
|
|
</indexterm>
|
|
<function>pg_event_trigger_table_rewrite_oid</function> ()
|
|
<returnvalue>oid</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns the OID of the table about to be rewritten.
|
|
</para></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>pg_event_trigger_table_rewrite_reason</primary>
|
|
</indexterm>
|
|
<function>pg_event_trigger_table_rewrite_reason</function> ()
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a code explaining the reason(s) for rewriting. The exact
|
|
meaning of the codes is release dependent.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
These functions can be used in an event trigger like this:
|
|
<programlisting>
|
|
CREATE FUNCTION test_event_trigger_table_rewrite_oid()
|
|
RETURNS event_trigger
|
|
LANGUAGE plpgsql AS
|
|
$$
|
|
BEGIN
|
|
RAISE NOTICE 'rewriting table % for reason %',
|
|
pg_event_trigger_table_rewrite_oid()::regclass,
|
|
pg_event_trigger_table_rewrite_reason();
|
|
END;
|
|
$$;
|
|
|
|
CREATE EVENT TRIGGER test_table_rewrite_oid
|
|
ON table_rewrite
|
|
EXECUTE FUNCTION test_event_trigger_table_rewrite_oid();
|
|
</programlisting>
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="functions-statistics">
|
|
<title>Statistics Information Functions</title>
|
|
|
|
<indexterm zone="functions-statistics">
|
|
<primary>function</primary>
|
|
<secondary>statistics</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> provides a function to inspect complex
|
|
statistics defined using the <command>CREATE STATISTICS</command> command.
|
|
</para>
|
|
|
|
<sect2 id="functions-statistics-mcv">
|
|
<title>Inspecting MCV Lists</title>
|
|
|
|
<indexterm>
|
|
<primary>pg_mcv_list_items</primary>
|
|
</indexterm>
|
|
|
|
<synopsis>
|
|
<function>pg_mcv_list_items</function> ( <type>pg_mcv_list</type> ) <returnvalue>setof record</returnvalue>
|
|
</synopsis>
|
|
|
|
<para>
|
|
<function>pg_mcv_list_items</function> returns a set of records describing
|
|
all items stored in a multi-column <acronym>MCV</acronym> list. It
|
|
returns the following columns:
|
|
|
|
<informaltable>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Type</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>index</literal></entry>
|
|
<entry><type>integer</type></entry>
|
|
<entry>index of the item in the <acronym>MCV</acronym> list</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>values</literal></entry>
|
|
<entry><type>text[]</type></entry>
|
|
<entry>values stored in the MCV item</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>nulls</literal></entry>
|
|
<entry><type>boolean[]</type></entry>
|
|
<entry>flags identifying <literal>NULL</literal> values</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>frequency</literal></entry>
|
|
<entry><type>double precision</type></entry>
|
|
<entry>frequency of this <acronym>MCV</acronym> item</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>base_frequency</literal></entry>
|
|
<entry><type>double precision</type></entry>
|
|
<entry>base frequency of this <acronym>MCV</acronym> item</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
</para>
|
|
|
|
<para>
|
|
The <function>pg_mcv_list_items</function> function can be used like this:
|
|
|
|
<programlisting>
|
|
SELECT m.* FROM pg_statistic_ext join pg_statistic_ext_data on (oid = stxoid),
|
|
pg_mcv_list_items(stxdmcv) m WHERE stxname = 'stts';
|
|
</programlisting>
|
|
|
|
Values of the <type>pg_mcv_list</type> type can be obtained only from the
|
|
<structname>pg_statistic_ext_data</structname>.<structfield>stxdmcv</structfield>
|
|
column.
|
|
</para>
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
</chapter>
|