This trivial patch implements disabled, deferred triggers, per my

proposal on -hackers a couple days ago. The 'tgenabled' status of the
trigger is consulted when the trigger is added to the deferred queue
(i.e. when the event occurs that fires the trigger), not when the
deferred event is executed.

No regression tests, as another bug prevents them (the pg_trigger row
for a trigger is only loaded once per session, so any changes to it are
not noticed unless the client disconnects and reconnects).

Neil Conway

src/backend/commands/trigger.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.142 2002/12/15 21:01:34 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.143 2003/01/08 22:28:32 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1456,7 +1456,9 @@ ExecBRUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
 			palloc0(trigdesc->numtriggers * sizeof(FmgrInfo));
 
 	LocTriggerData.type = T_TriggerData;
-	LocTriggerData.tg_event = TRIGGER_EVENT_UPDATE | TRIGGER_EVENT_ROW | TRIGGER_EVENT_BEFORE;
+	LocTriggerData.tg_event = TRIGGER_EVENT_UPDATE |
+							  TRIGGER_EVENT_ROW |
+							  TRIGGER_EVENT_BEFORE;
 	LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
 	for (i = 0; i < ntrigs; i++)
 	{
@@ -2323,6 +2325,7 @@ DeferredTriggerSaveEvent(ResultRelInfo *relinfo, int event, bool row_trigger,
 	int			new_size;
 	int			i;
 	int			ntriggers;
+	int			n_enabled_triggers = 0;
 	int		   *tgindx;
 	ItemPointerData oldctid;
 	ItemPointerData newctid;
@@ -2359,8 +2362,28 @@ DeferredTriggerSaveEvent(ResultRelInfo *relinfo, int event, bool row_trigger,
 		tgindx = trigdesc->tg_after_statement[event];
 	}
 
+	/*
+	 * Count the number of triggers that are actually enabled. Since we
+	 * only add enabled triggers to the queue, we only need allocate
+	 * enough space to hold them (and not any disabled triggers that may
+	 * be associated with the relation).
+	 */
+	for (i = 0; i < ntriggers; i++)
+	{
+		Trigger *trigger = &trigdesc->triggers[tgindx[i]];
+
+		if (trigger->tgenabled)
+			n_enabled_triggers++;
+	}
+
+	/*
+	 * If all the triggers on this relation are disabled, we're done.
+	 */
+	if (n_enabled_triggers == 0)
+		return;
+
 	new_size = offsetof(DeferredTriggerEventData, dte_item[0]) +
-		ntriggers * sizeof(DeferredTriggerEventItem);
+		n_enabled_triggers * sizeof(DeferredTriggerEventItem);
 
 	new_event = (DeferredTriggerEvent) palloc(new_size);
 	new_event->dte_next = NULL;
@@ -2373,9 +2396,13 @@ DeferredTriggerSaveEvent(ResultRelInfo *relinfo, int event, bool row_trigger,
 	new_event->dte_n_items = ntriggers;
 	for (i = 0; i < ntriggers; i++)
 	{
+		DeferredTriggerEventItem *ev_item;
 		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];
-		DeferredTriggerEventItem *ev_item = &(new_event->dte_item[i]);
 
+		if (!trigger->tgenabled)
+			continue;
+
+		ev_item = &(new_event->dte_item[i]);
 		ev_item->dti_tgoid = trigger->tgoid;
 		ev_item->dti_state = 
 			((trigger->tgdeferrable) ?