Function EventTriggerInvoke

src/backend/commands/event_trigger.c:872–930

* Invoke each event trigger in a list of event triggers. */

 * Invoke each event trigger in a list of event triggers.
 */
static void
EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata)
{
	MemoryContext context;
	MemoryContext oldcontext;
	ListCell   *lc;
	bool		first = true;

	/* Guard against stack overflow due to recursive event trigger */
	check_stack_depth();

	/*
	 * Let's evaluate event triggers in their own memory context, so that any
	 * leaks get cleaned up promptly.
	 */
	context = AllocSetContextCreate(CurrentMemoryContext,
									"event trigger context",
									ALLOCSET_DEFAULT_SIZES);
	oldcontext = MemoryContextSwitchTo(context);

	/* Call each event trigger. */
	foreach(lc, fn_oid_list)
	{
		LOCAL_FCINFO(fcinfo, 0);
		Oid			fnoid = lfirst_oid(lc);
		FmgrInfo	flinfo;
		PgStat_FunctionCallUsage fcusage;

		elog(DEBUG1, "EventTriggerInvoke %u", fnoid);

		/*
		 * We want each event trigger to be able to see the results of the
		 * previous event trigger's action.  Caller is responsible for any
		 * command-counter increment that is needed between the event trigger
		 * and anything else in the transaction.
		 */
		if (first)
			first = false;
		else
			CommandCounterIncrement();

		/* Look up the function */
		fmgr_info(fnoid, &flinfo);

		/* Call the function, passing no arguments but setting a context. */
		InitFunctionCallInfoData(*fcinfo, &flinfo, 0,
								 InvalidOid, (Node *) trigdata, NULL);
		pgstat_init_function_usage(fcinfo, &fcusage);
		FunctionCallInvoke(fcinfo);
		pgstat_end_function_usage(&fcusage, true);

		/* Reclaim memory. */
		MemoryContextReset(context);
	}

	/* Restore old memory context and delete the temporary one. */
	MemoryContextSwitchTo(oldcontext);
	MemoryContextDelete(context);