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PL/Perl: Add event trigger support

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From: Dimitri Fontaine <dimitri@2ndQuadrant.fr>
This commit is contained in:
Peter Eisentraut
2013-12-11 08:11:59 -05:00
parent 6bea96dd49
commit e5dc4cc24d
4 changed files with 242 additions and 11 deletions
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doc/src/sgml/plperl.sgml
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@ -1211,6 +1211,56 @@ CREATE TRIGGER test_valid_id_trig
</para>
</sect1>
<sect1 id="plperl-event-triggers">
<title>PL/Perl Event Triggers</title>
<para>
PL/Perl can be used to write event trigger functions. In an event trigger
function, the hash reference <varname>$_TD</varname> contains information
about the current trigger event. <varname>$_TD</> is a global variable,
which gets a separate local value for each invocation of the trigger. The
fields of the <varname>$_TD</varname> hash reference are:
<variablelist>
<varlistentry>
<term><literal>$_TD-&gt;{event}</literal></term>
<listitem>
<para>
The name of the event the trigger is fired for.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>$_TD-&gt;{tag}</literal></term>
<listitem>
<para>
The command tag for which the trigger is fired.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
The return value of the trigger procedure is ignored.
</para>
<para>
Here is an example of an event trigger function, illustrating some of the
above:
<programlisting>
CREATE OR REPLACE FUNCTION perlsnitch() RETURNS event_trigger AS $$
elog(NOTICE, "perlsnitch: " . $_TD->{event} . " " . $_TD->{tag} . " ");
$$ LANGUAGE plperl;
CREATE EVENT TRIGGER perl_a_snitch
ON ddl_command_start
EXECUTE PROCEDURE perlsnitch();
</programlisting>
</para>
</sect1>
<sect1 id="plperl-under-the-hood">
<title>PL/Perl Under the Hood</title>