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- PL/Perl can be used to write event trigger functions. In an event trigger
- function, the hash reference <code class="varname">$_TD</code> contains information
- about the current trigger event. <code class="varname">$_TD</code> is a global variable,
- which gets a separate local value for each invocation of the trigger. The
- fields of the <code class="varname">$_TD</code> hash reference are:
-
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">$_TD->{event}</code></span></dt><dd><p>
- The name of the event the trigger is fired for.
- </p></dd><dt><span class="term"><code class="literal">$_TD->{tag}</code></span></dt><dd><p>
- The command tag for which the trigger is fired.
- </p></dd></dl></div><p>
- </p><p>
- The return value of the trigger function is ignored.
- </p><p>
- Here is an example of an event trigger function, illustrating some of the
- above:
- </p><pre class="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 FUNCTION perlsnitch();
- </pre><p>
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