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A bit more wordsmithing on the COPY CSV NULL business.

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This commit is contained in:
Tom Lane 2009-09-18 20:01:18 +00:00
parent 8cc1c8c9f2
commit 4853c1eb2f
1 changed files with 12 additions and 8 deletions
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20
doc/src/sgml/ref/copy.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.85.2.2 2009/09/17 21:49:22 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.85.2.3 2009/09/18 20:01:18 tgl Exp $
PostgreSQL documentation
-->
@ -183,8 +183,8 @@ COPY { <replaceable class="parameter">tablename</replaceable> [ ( <replaceable c
<listitem>
<para>
The string that represents a null value. The default is
<literal>\N</literal> (backslash-N) in text mode, and a empty
value with no quotes in <literal>CSV</> mode. You might prefer an
<literal>\N</literal> (backslash-N) in text mode, and an unquoted empty
string in <literal>CSV</> mode. You might prefer an
empty string even in text mode for cases where you don't want to
distinguish nulls from empty strings.
</para>
@ -298,6 +298,10 @@ COPY <replaceable class="parameter">count</replaceable>
somewhat faster than the normal text mode, but a binary-format
file is less portable across machine architectures and
<productname>PostgreSQL</productname> versions.
Also, the binary format is very data type specific; for example
it will not work to output binary data from a <type>smallint</> column
and read it into an <type>integer</> column, even though that would work
fine in text format.
</para>
<para>
@ -544,11 +548,11 @@ COPY <replaceable class="parameter">count</replaceable>
<para>
The <literal>CSV</> format has no standard way to distinguish a
<literal>NULL</> value from an empty string.
<productname>PostgreSQL</>'s <command>COPY</> handles this by
quoting. A <literal>NULL</> is output as the <literal>NULL</>
parameter and is not quoted, while a non-NULL value matching the
the <literal>NULL</> parameter string is quoted. Therefore, using the default
settings, a <literal>NULL</> is written as an unquoted empty
<productname>PostgreSQL</>'s <command>COPY</> handles this by quoting.
A <literal>NULL</> is output as the <literal>NULL</> parameter string
and is not quoted, while a non-<literal>NULL</> value matching the
<literal>NULL</> parameter string is quoted. For example, with the
default settings, a <literal>NULL</> is written as an unquoted empty
string, while an empty string data value is written with double quotes
(<literal>""</>). Reading values follows similar rules. You can
use <literal>FORCE NOT NULL</> to prevent <literal>NULL</> input