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Ensure that BEFORE STATEMENT triggers fire the right number of times.

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Commit 0f79440fb introduced mechanism to keep AFTER STATEMENT triggers
from firing more than once per statement, which was formerly possible
if more than one FK enforcement action had to be applied to a given
table.  Add a similar mechanism for BEFORE STATEMENT triggers, so that
we don't have the unexpected situation of firing BEFORE STATEMENT
triggers more often than AFTER STATEMENT.

As with the previous patch, back-patch to v10.

Discussion: https://postgr.es/m/22315.1505584992@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2017-09-17 12:16:38 -04:00
parent cad22075bc
commit fd31f9f033
4 changed files with 87 additions and 17 deletions
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14
doc/src/sgml/ref/create_trigger.sgml
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@ -250,7 +250,8 @@ CREATE [ CONSTRAINT ] TRIGGER <replaceable class="PARAMETER">name</replaceable>
One of <literal>INSERT</literal>, <literal>UPDATE</literal>,
<literal>DELETE</literal>, or <literal>TRUNCATE</literal>;
this specifies the event that will fire the trigger. Multiple
events can be specified using <literal>OR</literal>.
events can be specified using <literal>OR</literal>, except when
transition relations are requested.
</para>
<para>
@ -263,7 +264,10 @@ UPDATE OF <replaceable>column_name1</replaceable> [, <replaceable>column_name2</
is mentioned as a target of the <command>UPDATE</> command.
</para>
<para><literal>INSTEAD OF UPDATE</> events do not support lists of columns.
<para>
<literal>INSTEAD OF UPDATE</> events do not allow a list of columns.
A column list cannot be specified when requesting transition relations,
either.
</para>
</listitem>
</varlistentry>
@ -490,9 +494,9 @@ UPDATE OF <replaceable>column_name1</replaceable> [, <replaceable>column_name2</
trigger that requests transition relations will cause the foreign-key
enforcement actions triggered by a single SQL command to be split into
multiple steps, each with its own transition relation(s). In such cases,
any <literal>AFTER STATEMENT</> triggers that are present will be fired
once per creation of a transition relation, ensuring that the triggers see
each affected row once and only once.
any statement-level triggers that are present will be fired once per
creation of a transition relation set, ensuring that the triggers see
each affected row in a transition relation once and only once.
</para>
<para>