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<title>39.2.Trigger Functions</title>
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<a name="plpython-trigger"></a>39.2.Trigger Functions</h2></div></div></div>
<a name="id733236"></a><p> When a function is used as a trigger, the dictionary
<code class="literal">TD</code> contains trigger-related values. The trigger
rows are in <code class="literal">TD["new"]</code> and/or <code class="literal">TD["old"]</code>
depending on the trigger event. <code class="literal">TD["event"]</code> contains
the event as a string (<code class="literal">INSERT</code>, <code class="literal">UPDATE</code>,
<code class="literal">DELETE</code>, or <code class="literal">UNKNOWN</code>).
<code class="literal">TD["when"]</code> contains one of <code class="literal">BEFORE</code>,
<code class="literal">AFTER</code>, and <code class="literal">UNKNOWN</code>.
<code class="literal">TD["level"]</code> contains one of <code class="literal">ROW</code>,
<code class="literal">STATEMENT</code>, and <code class="literal">UNKNOWN</code>.
<code class="literal">TD["name"]</code> contains the trigger name, and
<code class="literal">TD["relid"]</code> contains the OID of the table on
which the trigger occurred. If the <code class="command">CREATE TRIGGER</code> command
included arguments, they are available in <code class="literal">TD["args"][0]</code> to
<code class="literal">TD["args"][(<em class="replaceable"><code>n</code></em>-1)]</code>.
</p>
<p> If <code class="literal">TD["when"]</code> is <code class="literal">BEFORE</code>, you may
return <code class="literal">None</code> or <code class="literal">"OK"</code> from the
Python function to indicate the row is unmodified,
<code class="literal">"SKIP"</code> to abort the event, or <code class="literal">"MODIFY"</code> to
indicate you've modified the row.
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