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Add documentation about the behavior of BEFORE triggers and referential

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integrity actions.

Stephan Szabo
This commit is contained in:
Bruce Momjian 2005-12-09 19:39:41 +00:00
parent 9c9b9446da
commit ede54f3cd7
1 changed files with 14 additions and 2 deletions
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16
doc/src/sgml/ref/create_trigger.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.42 2005/11/01 21:09:50 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.43 2005/12/09 19:39:41 momjian Exp $
PostgreSQL documentation
-->
@ -241,13 +241,25 @@ CREATE TRIGGER <replaceable class="PARAMETER">name</replaceable> { BEFORE | AFTE
function that executes the desired commands.
</para>
</listitem>
</itemizedlist>
</para>
<para>
SQL specifies that multiple triggers should be fired in
time-of-creation order. <productname>PostgreSQL</productname> uses
name order, which was judged more convenient to work with.
name order, which was judged to be more convenient.
</para>
<para>
SQL specifies that <literal>BEFORE DELETE</literal> triggers on cascaded
deletes fire <emphasis>after</> the cascaded <literal>DELETE</> completes.
The <productname>PostgreSQL</productname> behavior is for <literal>BEFORE
DELETE</literal> to always fire before the delete action, even a cascading
one. This is considered more consistent. There is also unpredictable
behavior when <literal>BEFORE</literal> triggers modify rows that are later
to be modified by referential actions. This can lead to contraint violations
or stored data that does not honor the referential constraint.
</para>
<para>