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Improve documentation of trigger firing queue handling, cleanup.

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Neil Conway
This commit is contained in:
Bruce Momjian
2002-08-17 12:15:49 +00:00
parent 2132ac89bf
commit b813554dbd
5 changed files with 319 additions and 181 deletions
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38
doc/src/sgml/ref/set_constraints.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_constraints.sgml,v 1.4 2002/06/03 01:10:38 momjian Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_constraints.sgml,v 1.5 2002/08/17 12:15:48 momjian Exp $ -->
<refentry id="SQL-SET-CONSTRAINTS">
<refmeta>
<refentrytitle id="SQL-SET-CONSTRAINTS-title">SET CONSTRAINTS</refentrytitle>
@ -22,10 +22,32 @@ SET CONSTRAINTS { ALL | <replaceable class="parameter">constraint</replaceable>
<para>
<command>SET CONSTRAINTS</command> sets the behavior of constraint
evaluation in the current transaction. In
<option>IMMEDIATE</option> mode, constraints are checked at the end
of each statement. In <option>DEFERRED</option> mode, constraints
are not checked until transaction commit.
evaluation in the current transaction. In <option>IMMEDIATE
</option> mode, constraints are checked at the end of each
statement. In <option>DEFERRED</option> mode, constraints are not
checked until transaction commit.
</para>
<note>
<para>
This command only alters the behavior of constraints within the
current transaction. Thus, if you execute this command outside
of an explicit transaction block (such as one started with
<command>BEGIN</command>), it will not appear to have any effect.
If you wish to change the behavior of a constraint without needing
to issue a <command>SET CONSTRAINTS</command> command in every
transaction, specify <option>INITIALLY DEFERRED</option> or
<option>INITIALLY IMMEDIATE</option> when you create the constraint.
</para>
</note>
<para>
When you change the mode of a constraint to be <option>IMMEDIATE
</option>, the new constraint mode takes effect retroactively:
any outstanding data modifications that would have been checked
at the end of the transaction (when using
<option>DEFERRED</option>) are instead checked during the
execution of the <command>SET CONSTRAINTS</command> command.
</para>
<para>
@ -52,7 +74,11 @@ SET CONSTRAINTS { ALL | <replaceable class="parameter">constraint</replaceable>
<para>
<command>SET CONSTRAINTS</command> is defined in
<acronym>SQL92</acronym> and <acronym>SQL99</acronym>.
<acronym>SQL92</acronym> and <acronym>SQL99</acronym>. The
implementation in <productname>PostgreSQL</productname> complies
with the behavior defined in the standard, except for the
<productname>PostgreSQL</productname> limitation that <command>SET
CONSTRAINTS</command> cannot be applied to check or unique constraints.
</para>
</refsect2>
</refsect1>