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981 lines
23 KiB
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981 lines
23 KiB
Plaintext
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.35 2000/03/31 17:45:32 tgl Exp $
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Postgres documentation
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-->
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<refentry id="SQL-SET">
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<refmeta>
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<refentrytitle id="SQL-SET-TITLE">
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SET
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</refentrytitle>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>
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SET
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</refname>
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<refpurpose>
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Set run-time parameters for session
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</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<refsynopsisdivinfo>
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<date>1999-07-20</date>
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</refsynopsisdivinfo>
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<synopsis>
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SET <replaceable class="PARAMETER">variable</replaceable> { TO | = } { <replaceable class="PARAMETER">value</replaceable> | '<replaceable class="PARAMETER">value</replaceable>' | DEFAULT }
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SET TIME ZONE { '<replaceable class="PARAMETER">timezone</replaceable>' | LOCAL | DEFAULT }
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SET TRANSACTION ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE }
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</synopsis>
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<refsect2 id="R2-SQL-SET-1">
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<refsect2info>
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<date>1998-09-24</date>
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</refsect2info>
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<title>
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Inputs
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</title>
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<para>
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<variablelist>
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<varlistentry>
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<term><replaceable class="PARAMETER">variable</replaceable></term>
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<listitem>
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<para>
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Settable global parameter.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="PARAMETER">value</replaceable></term>
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<listitem>
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<para>
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New value of parameter. <option>DEFAULT</option> can be
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used to specify resetting the parameter to its default
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value. Lists of strings are allowed, but more complex
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|
constructs may need to be single or double quoted.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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The possible variables and allowed values are:
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<variablelist>
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<varlistentry>
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<term>CLIENT_ENCODING | NAMES</term>
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<listitem>
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<para>
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Sets the multi-byte client encoding. Parameters are:
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<variablelist>
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<varlistentry>
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<term><replaceable class="parameter">value</replaceable></term>
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<listitem>
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<para>
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Sets the multi-byte client encoding to
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<replaceable class="parameter">value</replaceable>.
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The specified encoding must be supported by the backend.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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This option is only available if MULTIBYTE support was enabled
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|
during the configure step of building Postgres.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>DateStyle</term>
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<listitem>
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<para>
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Set the date/time representation style. Affects the output format,
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and in some cases it can affect the interpretation of input.
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<variablelist>
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<varlistentry>
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<term>ISO</term>
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<listitem>
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<para>
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use ISO 8601-style dates and times
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>SQL</term>
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<listitem>
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<para>
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use Oracle/Ingres-style dates and times
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Postgres</term>
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<listitem>
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<para>
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use traditional <productname>Postgres</productname> format
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>European</term>
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<listitem>
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<para>
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use <literal>dd/mm/yyyy</literal> for numeric date representations.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>NonEuropean</term>
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<listitem>
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<para>
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use <literal>mm/dd/yyyy</literal> for numeric date representations.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>German</term>
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<listitem>
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<para>
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use <literal>dd.mm.yyyy</literal> for numeric date representations.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>US</term>
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<listitem>
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<para>
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|
same as <literal>NonEuropean</literal>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>DEFAULT</term>
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<listitem>
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|
<para>
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restores the default values (<literal>US,Postgres</literal>)
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</para>
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|
</listitem>
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|
</varlistentry>
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|
</variablelist>
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|
</para>
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<para>
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Date format initialization may be done by:
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<simplelist>
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<member>
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Setting the <envar>PGDATESTYLE</envar> environment variable.
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If PGDATESTYLE is set in the frontend environment of a client
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|
based on libpq, libpq will automatically set DATESTYLE to the
|
|
value of PGDATESTYLE during connection startup.
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|
</member>
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<member>
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Running postmaster using the option <option>-o -e</option> to set
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dates to the <literal>European</literal> convention.
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Note that this affects only some combinations of date styles; for example
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the ISO style is not affected by this parameter.
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</member>
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<member>
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|
Changing variables in
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<filename>src/backend/utils/init/globals.c</filename>.
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|
</member>
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|
</simplelist>
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|
</para>
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<para>
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The variables in <filename>globals.c</filename> which can be changed are:
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<simplelist>
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<member>
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bool EuroDates = false | true
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</member>
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<member>
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int DateStyle = USE_ISO_DATES | USE_POSTGRES_DATES | USE_SQL_DATES | USE_GERMAN_DATES
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</member>
|
|
</simplelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SERVER_ENCODING</term>
|
|
<listitem>
|
|
<para>
|
|
Sets the multi-byte server encoding
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable class="parameter">value</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Sets the multi-byte server encoding.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
|
|
<para>
|
|
This option is only available if MULTIBYTE support was enabled
|
|
during the configure step of building Postgres.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>TIMEZONE</term>
|
|
<listitem>
|
|
<para>
|
|
The possible values for timezone depends on your operating
|
|
system. For example on Linux /usr/lib/zoneinfo contains the
|
|
database of timezones.
|
|
</para>
|
|
<para>
|
|
Here are some valid values for timezone:
|
|
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|
<variablelist>
|
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<varlistentry>
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<term>PST8PDT</term>
|
|
<listitem>
|
|
<para>
|
|
set the timezone for California
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|
</para>
|
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</listitem>
|
|
</varlistentry>
|
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<varlistentry>
|
|
<term>Portugal</term>
|
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<listitem>
|
|
<para>
|
|
set time zone for Portugal.
|
|
</para>
|
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</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>'Europe/Rome'</term>
|
|
<listitem>
|
|
<para>
|
|
set time zone for Italy.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term>DEFAULT</term>
|
|
<listitem>
|
|
<para>
|
|
set time zone to your local timezone
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|
(value of the TZ environment variable).
|
|
</para>
|
|
</listitem>
|
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</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
<para>
|
|
If an invalid time zone is specified, the time zone
|
|
becomes GMT (on most systems anyway).
|
|
</para>
|
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<para>
|
|
The second syntax shown above, allows one to set the timezone
|
|
with a syntax similar to SQL92 <command>SET TIME ZONE</command>.
|
|
The LOCAL keyword is just an alternate form
|
|
of DEFAULT for SQL92 compatibility.
|
|
</para>
|
|
<para>
|
|
If the PGTZ environment variable is set in the frontend
|
|
environment of a client based on libpq, libpq will automatically
|
|
set TIMEZONE to the value of PGTZ during connection startup.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>TRANSACTION ISOLATION LEVEL</term>
|
|
<listitem>
|
|
<para>
|
|
Sets the isolation level for the current transaction.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>READ COMMITTED</term>
|
|
<listitem>
|
|
<para>
|
|
The current transaction queries read only rows committed
|
|
before a query began. READ COMMITTED is the default.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
<acronym>SQL92</acronym> standard requires
|
|
SERIALIZABLE to be the default isolation level.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SERIALIZABLE</term>
|
|
<listitem>
|
|
<para>
|
|
The current transaction queries read only rows committed
|
|
before first DML statement
|
|
(<command>SELECT/INSERT/DELETE/UPDATE/FETCH/COPY_TO</command>)
|
|
was executed in this transaction.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
|
|
<para>
|
|
There are also several internal or optimization
|
|
parameters which can be specified
|
|
by the <command>SET</command> command:
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>RANDOM_PAGE_COST</term>
|
|
<listitem>
|
|
<para>
|
|
Sets the optimizer's estimate of the cost of a nonsequentially
|
|
fetched disk page. This is measured as a multiple of the cost
|
|
of a sequential page fetch.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable class="parameter">float8</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Set the cost of a random page access
|
|
to the specified floating-point value.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>CPU_TUPLE_COST</term>
|
|
<listitem>
|
|
<para>
|
|
Sets the optimizer's estimate of the cost of processing each
|
|
tuple during a query. This is measured as a fraction of the cost
|
|
of a sequential page fetch.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable class="parameter">float8</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Set the cost of per-tuple CPU processing
|
|
to the specified floating-point value.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>CPU_INDEX_TUPLE_COST</term>
|
|
<listitem>
|
|
<para>
|
|
Sets the optimizer's estimate of the cost of processing each
|
|
index tuple during an index scan. This is measured as a fraction
|
|
of the cost of a sequential page fetch.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable class="parameter">float8</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Set the cost of per-index-tuple CPU processing
|
|
to the specified floating-point value.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>CPU_OPERATOR_COST</term>
|
|
<listitem>
|
|
<para>
|
|
Sets the optimizer's estimate of the cost of processing each
|
|
operator in a WHERE clause. This is measured as a fraction
|
|
of the cost of a sequential page fetch.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable class="parameter">float8</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Set the cost of per-operator CPU processing
|
|
to the specified floating-point value.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>EFFECTIVE_CACHE_SIZE</term>
|
|
<listitem>
|
|
<para>
|
|
Sets the optimizer's assumption about the effective size of the
|
|
disk cache (that is, the portion of the kernel's disk cache that
|
|
will be used for Postgres data files). This is measured in disk
|
|
pages, which are normally 8Kb apiece.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable class="parameter">float8</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Set the assumed cache size
|
|
to the specified floating-point value.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ENABLE_SEQSCAN</term>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the planner's use of sequential scan plan types.
|
|
(It's not possible to suppress sequential scans entirely, but turning
|
|
this variable OFF discourages the planner from using one if there is
|
|
any other method available.)
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>ON</term>
|
|
<listitem>
|
|
<para>
|
|
enables use of sequential scans (default setting).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>OFF</term>
|
|
<listitem>
|
|
<para>
|
|
disables use of sequential scans.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ENABLE_INDEXSCAN</term>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the planner's use of index scan plan types.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>ON</term>
|
|
<listitem>
|
|
<para>
|
|
enables use of index scans (default setting).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>OFF</term>
|
|
<listitem>
|
|
<para>
|
|
disables use of index scans.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ENABLE_TIDSCAN</term>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the planner's use of TID scan plan types.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>ON</term>
|
|
<listitem>
|
|
<para>
|
|
enables use of TID scans (default setting).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>OFF</term>
|
|
<listitem>
|
|
<para>
|
|
disables use of TID scans.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ENABLE_SORT</term>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the planner's use of explicit sort steps.
|
|
(It's not possible to suppress explicit sorts entirely, but turning
|
|
this variable OFF discourages the planner from using one if there is
|
|
any other method available.)
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>ON</term>
|
|
<listitem>
|
|
<para>
|
|
enables use of sorts (default setting).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>OFF</term>
|
|
<listitem>
|
|
<para>
|
|
disables use of sorts.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ENABLE_NESTLOOP</term>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the planner's use of nested-loop join plans.
|
|
(It's not possible to suppress nested-loop joins entirely, but turning
|
|
this variable OFF discourages the planner from using one if there is
|
|
any other method available.)
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>ON</term>
|
|
<listitem>
|
|
<para>
|
|
enables use of nested-loop joins (default setting).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>OFF</term>
|
|
<listitem>
|
|
<para>
|
|
disables use of nested-loop joins.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ENABLE_MERGEJOIN</term>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the planner's use of mergejoin plans.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>ON</term>
|
|
<listitem>
|
|
<para>
|
|
enables use of merge joins (default setting).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>OFF</term>
|
|
<listitem>
|
|
<para>
|
|
disables use of merge joins.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ENABLE_HASHJOIN</term>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the planner's use of hashjoin plans.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>ON</term>
|
|
<listitem>
|
|
<para>
|
|
enables use of hash joins (default setting).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>OFF</term>
|
|
<listitem>
|
|
<para>
|
|
disables use of hash joins.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>GEQO</term>
|
|
<listitem>
|
|
<para>
|
|
Sets the threshold for using the genetic optimizer algorithm.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>ON</term>
|
|
<listitem>
|
|
<para>
|
|
enables the genetic optimizer algorithm
|
|
for statements with 11 or more tables.
|
|
(This is also the DEFAULT setting.)
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ON=<replaceable class="parameter">#</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Takes an integer argument to enable the genetic optimizer algorithm
|
|
for statements with <replaceable class="parameter">#</replaceable>
|
|
or more tables in the query.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>OFF</term>
|
|
<listitem>
|
|
<para>
|
|
disables the genetic optimizer algorithm.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
|
|
<para>
|
|
See the chapter on GEQO in the Programmer's Guide
|
|
for more information about query optimization.
|
|
</para>
|
|
<para>
|
|
If the PGGEQO environment variable is set in the frontend
|
|
environment of a client based on libpq, libpq will automatically
|
|
set GEQO to the value of PGGEQO during connection startup.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>KSQO</term>
|
|
<listitem>
|
|
<para>
|
|
<firstterm>Key Set Query Optimizer</firstterm> causes the query
|
|
planner to convert queries whose WHERE clause contains many
|
|
OR'ed AND clauses (such as "WHERE (a=1 AND b=2) OR (a=2 AND b=3) ...")
|
|
into a UNION query. This method can be faster than the default
|
|
implementation, but it doesn't necessarily give exactly the same
|
|
results, since UNION implicitly adds a SELECT DISTINCT clause to
|
|
eliminate identical output rows. KSQO is commonly used when
|
|
working with products like <productname>MicroSoft
|
|
Access</productname>, which tend to generate queries of this form.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>ON</term>
|
|
<listitem>
|
|
<para>
|
|
enables this optimization.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>OFF</term>
|
|
<listitem>
|
|
<para>
|
|
disables this optimization (default setting).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>DEFAULT</term>
|
|
<listitem>
|
|
<para>
|
|
Equivalent to specifying <command>SET KSQO=OFF</command>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
|
|
<para>
|
|
The KSQO algorithm used to be absolutely essential for queries
|
|
with many OR'ed AND clauses, but in Postgres 7.0 and later
|
|
the standard planner handles these queries fairly successfully.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>MAX_EXPR_DEPTH</term>
|
|
<listitem>
|
|
<para>
|
|
Sets the maximum expression nesting depth that the parser will
|
|
accept. The default value is high enough for any normal query,
|
|
but you can raise it if you need to. (But if you raise it too high,
|
|
you run the risk of backend crashes due to stack overflow.)
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable class="parameter">integer</replaceable></term>
|
|
<listitem>
|
|
<para>
|
|
Maximum depth.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</para>
|
|
</refsect2>
|
|
|
|
<refsect2 id="R2-SQL-SET-2">
|
|
<refsect2info>
|
|
<date>1998-09-24</date>
|
|
</refsect2info>
|
|
<title>
|
|
Outputs
|
|
</title>
|
|
<para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><computeroutput>
|
|
SET VARIABLE
|
|
</computeroutput></term>
|
|
<listitem>
|
|
<para>
|
|
Message returned if successfully.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><computeroutput>
|
|
WARN: Bad value for <replaceable class="parameter">variable</replaceable> (<replaceable class="parameter">value</replaceable>)
|
|
</computeroutput></term>
|
|
<listitem>
|
|
<para>
|
|
If the command fails to set the specified variable.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</para>
|
|
</refsect2>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1 id="R1-SQL-SET-1">
|
|
<refsect1info>
|
|
<date>1998-09-24</date>
|
|
</refsect1info>
|
|
<title>
|
|
Description
|
|
</title>
|
|
<para>
|
|
<command>SET</command> will modify configuration parameters for variable during
|
|
a session.
|
|
</para>
|
|
<para>
|
|
Current values can be obtained using <command>SHOW</command>, and values
|
|
can be restored to the defaults using <command>RESET</command>.
|
|
Parameters and values are case-insensitive. Note that the value
|
|
field is always specified as a string, so is enclosed in
|
|
single-quotes.
|
|
</para>
|
|
<para>
|
|
<command>SET TIME ZONE</command> changes the session's
|
|
default time zone offset.
|
|
An SQL-session always begins with an initial default time zone
|
|
offset.
|
|
The <command>SET TIME ZONE</command> statement is used to change the default
|
|
time zone offset for the current SQL session.
|
|
</para>
|
|
|
|
<refsect2 id="R2-SQL-SET-3">
|
|
<refsect2info>
|
|
<date>1998-09-24</date>
|
|
</refsect2info>
|
|
<title>
|
|
Notes
|
|
</title>
|
|
<para>
|
|
The <command>SET <replaceable class="parameter">variable</replaceable></command>
|
|
statement is a <productname>Postgres</productname> language extension.
|
|
</para>
|
|
<para>
|
|
Refer to <command>SHOW</command> and <command>RESET</command> to
|
|
display or reset the current values.
|
|
</para>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<refsect1 id="R1-SQL-SET-2">
|
|
<title>
|
|
Usage
|
|
</title>
|
|
<para>
|
|
Set the style of date to ISO (no quotes on the argument is required):
|
|
|
|
<programlisting>
|
|
SET DATESTYLE TO ISO;
|
|
</programlisting>
|
|
|
|
Enable GEQO for queries with 4 or more tables (note the use of
|
|
single quotes to handle the equal sign inside the value argument):
|
|
|
|
<programlisting>
|
|
SET GEQO = 'ON=4';
|
|
</programlisting>
|
|
|
|
Set GEQO to default:
|
|
|
|
<programlisting>
|
|
SET GEQO = DEFAULT;
|
|
</programlisting>
|
|
|
|
Set the timezone for Berkeley, California, using double quotes to
|
|
preserve the uppercase
|
|
attributes of the time zone specifier:
|
|
|
|
<programlisting>
|
|
SET TIME ZONE "PST8PDT";
|
|
SELECT CURRENT_TIMESTAMP AS today;
|
|
|
|
today
|
|
------------------------
|
|
1998-03-31 07:41:21-08
|
|
</programlisting>
|
|
|
|
Set the timezone for Italy (note the required single or double quotes to handle
|
|
the special characters):
|
|
|
|
<programlisting>
|
|
SET TIME ZONE 'Europe/Rome';
|
|
SELECT CURRENT_TIMESTAMP AS today;
|
|
|
|
today
|
|
------------------------
|
|
1998-03-31 17:41:31+02
|
|
</programlisting>
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1 id="R1-SQL-SET-3">
|
|
<title>
|
|
Compatibility
|
|
</title>
|
|
|
|
<refsect2 id="R2-SQL-SET-4">
|
|
<refsect2info>
|
|
<date>1998-09-24</date>
|
|
</refsect2info>
|
|
<title>
|
|
SQL92
|
|
</title>
|
|
<para>
|
|
There is no general
|
|
<command>SET <replaceable class="parameter">variable</replaceable></command>
|
|
in <acronym>SQL92</acronym> (with the exception of
|
|
<command>SET TRANSACTION ISOLATION LEVEL</command>).
|
|
|
|
The <acronym>SQL92</acronym> syntax for <command>SET TIME ZONE</command>
|
|
is slightly different,
|
|
allowing only a single integer value for time zone specification:
|
|
|
|
<synopsis>
|
|
SET TIME ZONE { interval_value_expression | LOCAL }
|
|
</synopsis>
|
|
</para>
|
|
</refsect2>
|
|
</refsect1>
|
|
</refentry>
|
|
|
|
<!-- Keep this comment at the end of the file
|
|
Local variables:
|
|
mode:sgml
|
|
sgml-omittag:nil
|
|
sgml-shorttag:t
|
|
sgml-minimize-attributes:nil
|
|
sgml-always-quote-attributes:t
|
|
sgml-indent-step:1
|
|
sgml-indent-data:t
|
|
sgml-parent-document:nil
|
|
sgml-default-dtd-file:"../reference.ced"
|
|
sgml-exposed-tags:nil
|
|
sgml-local-catalogs:("/usr/lib/sgml/catalog")
|
|
sgml-local-ecat-files:nil
|
|
End:
|
|
-->
|