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Fix inaccurate description of deferrable unique constraints, per Dean Rasheed.

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This commit is contained in:
Tom Lane 2010-08-06 18:55:24 +00:00
parent 7ae6163a4e
commit a209b9850f
1 changed files with 10 additions and 6 deletions
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16
doc/src/sgml/release-9.0.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/release-9.0.sgml,v 2.45 2010/08/06 17:56:43 rhaas Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/release-9.0.sgml,v 2.46 2010/08/06 18:55:24 tgl Exp $ -->
<sect1 id="release-9-0">
<title>Release 9.0</title>
@ -91,7 +91,8 @@
<listitem>
<para>
<link linkend="SQL-CREATETABLE-compatibility">Deferrable
unique constraints, now permit mass updates to unique keys.</link>
unique constraints. Mass updates to unique keys are now possible
without trickery.</link>
</para>
</listitem>
@ -1122,10 +1123,13 @@
</para>
<para>
This allows <command>UPDATE tab SET col = col + 1</> to work on
columns that have a unique indexes or are marked as primary key,
but <literal>DEFERRABLE INITIALLY DEFERRED</> must be used to mark
the constraint as deferred.
This allows <command>UPDATE tab SET col = col + 1</> to work reliably
on columns that have unique indexes or are marked as primary keys.
If the constraint is specified as <literal>DEFERRABLE</> it will be
checked at the end of the statement, rather than after each row is
updated. The constraint check may also be deferred until the end of the
current transaction, allowing updates to be spread over multiple SQL
commands.
</para>
</listitem>