In an attempt to simplify my life I'm submitting this patch that

restructures the deferred trigger queue.  The fundamental change is to
put all the static variables to hold the deferred triggers in a single
structure.

Alvaro Herrera

Author: bmomjian

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 1.148 2003/04/20 17:03:25 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.149 2003/06/24 23:25:44 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1601,25 +1601,22 @@ ltrmark:;
  * ----------
  */
 
-
-/*
- * Internal data to the deferred trigger mechanism is held over
- * statements/commands in a context which is created at transaction
- * start and destroyed at transaction end.
- */
-
-static MemoryContext deftrig_cxt = NULL;
-
-/* ----------
- * Global data that tells which triggers are actually in
- * state IMMEDIATE or DEFERRED.
- * ----------
- */
-static bool deftrig_all_isset = false;
-static bool deftrig_all_isdeferred = false;
-static List *deftrig_trigstates;
+typedef struct DeferredTriggersData {
+		/* Internal data is held in a per-transaction memory context */
+	MemoryContext			deftrig_cxt;
+		/* ALL DEFERRED or ALL IMMEDIATE */
+	bool					deftrig_all_isset;
+	bool					deftrig_all_isdeferred;
+		/* Per trigger state */
+	List		  		   *deftrig_trigstates;
+		/* List of pending deferred triggers. Previous comment below */
+	DeferredTriggerEvent	deftrig_events;
+	DeferredTriggerEvent	deftrig_events_imm;
+	DeferredTriggerEvent	deftrig_event_tail;
+} DeferredTriggersData;
 
 /* ----------
+ * deftrig_events, deftrig_event_tail:
  * The list of pending deferred trigger events during the current transaction.
  *
  * deftrig_events is the head, deftrig_event_tail is the last entry.
@@ -1636,10 +1633,10 @@ static List *deftrig_trigstates;
  *	   large...
  * ----------
  */
-static DeferredTriggerEvent deftrig_events;
-static DeferredTriggerEvent deftrig_events_imm;
-static DeferredTriggerEvent deftrig_event_tail;
 
+typedef DeferredTriggersData *DeferredTriggers;
+
+static DeferredTriggers	deferredTriggers;
 
 /* ----------
  * deferredTriggerCheckState()
@@ -1665,7 +1662,7 @@ deferredTriggerCheckState(Oid tgoid, int32 itemstate)
 	/*
 	 * Lookup if we know an individual state for this trigger
 	 */
-	foreach(sl, deftrig_trigstates)
+	foreach(sl, deferredTriggers->deftrig_trigstates)
 	{
 		trigstate = (DeferredTriggerStatus) lfirst(sl);
 		if (trigstate->dts_tgoid == tgoid)
@@ -1676,21 +1673,22 @@ deferredTriggerCheckState(Oid tgoid, int32 itemstate)
 	 * No individual state known - so if the user issued a SET CONSTRAINT
 	 * ALL ..., we return that instead of the triggers default state.
 	 */
-	if (deftrig_all_isset)
-		return deftrig_all_isdeferred;
+	if (deferredTriggers->deftrig_all_isset)
+		return deferredTriggers->deftrig_all_isdeferred;
 
 	/*
 	 * No ALL state known either, remember the default state as the
 	 * current and return that.
 	 */
-	oldcxt = MemoryContextSwitchTo(deftrig_cxt);
+	oldcxt = MemoryContextSwitchTo(deferredTriggers->deftrig_cxt);
 
 	trigstate = (DeferredTriggerStatus)
 		palloc(sizeof(DeferredTriggerStatusData));
 	trigstate->dts_tgoid = tgoid;
 	trigstate->dts_tgisdeferred =
 		((itemstate & TRIGGER_DEFERRED_INITDEFERRED) != 0);
-	deftrig_trigstates = lappend(deftrig_trigstates, trigstate);
+	deferredTriggers->deftrig_trigstates =
+		lappend(deferredTriggers->deftrig_trigstates, trigstate);
 
 	MemoryContextSwitchTo(oldcxt);
 
@@ -1713,16 +1711,16 @@ deferredTriggerAddEvent(DeferredTriggerEvent event)
 	 * "lappend". This avoids O(N^2) behavior for large numbers of events.
 	 */
 	event->dte_next = NULL;
-	if (deftrig_event_tail == NULL)
+	if (deferredTriggers->deftrig_event_tail == NULL)
 	{
 		/* first list entry */
-		deftrig_events = event;
-		deftrig_event_tail = event;
+		deferredTriggers->deftrig_events = event;
+		deferredTriggers->deftrig_event_tail = event;
 	}
 	else
 	{
-		deftrig_event_tail->dte_next = event;
-		deftrig_event_tail = event;
+		deferredTriggers->deftrig_event_tail->dte_next = event;
+		deferredTriggers->deftrig_event_tail = event;
 	}
 }
 
@@ -1884,15 +1882,15 @@ deferredTriggerInvokeEvents(bool immediate_only)
 	 * are those since deftrig_events_imm.  (But if deftrig_events_imm is
 	 * NULL, we must scan the entire list.)
 	 */
-	if (immediate_only && deftrig_events_imm != NULL)
+	if (immediate_only && deferredTriggers->deftrig_events_imm != NULL)
 	{
-		prev_event = deftrig_events_imm;
+		prev_event = deferredTriggers->deftrig_events_imm;
 		event = prev_event->dte_next;
 	}
 	else
 	{
 		prev_event = NULL;
-		event = deftrig_events;
+		event = deferredTriggers->deftrig_events;
 	}
 
 	while (event != NULL)
@@ -1994,7 +1992,7 @@ deferredTriggerInvokeEvents(bool immediate_only)
 				if (prev_event)
 					prev_event->dte_next = next_event;
 				else
-					deftrig_events = next_event;
+					deferredTriggers->deftrig_events = next_event;
 				pfree(event);
 			}
 			else
@@ -2011,10 +2009,10 @@ deferredTriggerInvokeEvents(bool immediate_only)
 	}
 
 	/* Update list tail pointer in case we just deleted tail event */
-	deftrig_event_tail = prev_event;
+	deferredTriggers->deftrig_event_tail = prev_event;
 
 	/* Set the immediate event pointer for next time */
-	deftrig_events_imm = prev_event;
+	deferredTriggers->deftrig_events_imm = prev_event;
 
 	/* Release working resources */
 	if (rel)
@@ -2052,30 +2050,32 @@ DeferredTriggerInit(void)
 void
 DeferredTriggerBeginXact(void)
 {
-	if (deftrig_cxt != NULL)
-		elog(ERROR,
-		   "DeferredTriggerBeginXact() called while inside transaction");
+	/*
+	 * This will be changed to a special context when
+	 * the nested transactions project moves forward.
+	 */
+	MemoryContext cxt = TopTransactionContext;
+	deferredTriggers = (DeferredTriggers) MemoryContextAlloc(TopTransactionContext,
+			sizeof(DeferredTriggersData));
 
 	/*
 	 * Create the per transaction memory context
 	 */
-	deftrig_cxt = AllocSetContextCreate(TopTransactionContext,
+	deferredTriggers->deftrig_cxt = AllocSetContextCreate(cxt,
 										"DeferredTriggerXact",
 										ALLOCSET_DEFAULT_MINSIZE,
 										ALLOCSET_DEFAULT_INITSIZE,
 										ALLOCSET_DEFAULT_MAXSIZE);
-	deftrig_all_isset = false;
-
 	/*
 	 * If unspecified, constraints default to IMMEDIATE, per SQL
 	 */
-	deftrig_all_isdeferred = false;
+	deferredTriggers->deftrig_all_isdeferred = false;
+	deferredTriggers->deftrig_all_isset = false;
 
-	deftrig_trigstates = NIL;
-
-	deftrig_events = NULL;
-	deftrig_events_imm = NULL;
-	deftrig_event_tail = NULL;
+	deferredTriggers->deftrig_trigstates = NIL;
+	deferredTriggers->deftrig_events = NULL;
+	deferredTriggers->deftrig_events_imm = NULL;
+	deferredTriggers->deftrig_event_tail = NULL;
 }
 
 
@@ -2092,7 +2092,7 @@ DeferredTriggerEndQuery(void)
 	/*
 	 * Ignore call if we aren't in a transaction.
 	 */
-	if (deftrig_cxt == NULL)
+	if (deferredTriggers == NULL)
 		return;
 
 	deferredTriggerInvokeEvents(true);
@@ -2112,13 +2112,12 @@ DeferredTriggerEndXact(void)
 	/*
 	 * Ignore call if we aren't in a transaction.
 	 */
-	if (deftrig_cxt == NULL)
+	if (deferredTriggers == NULL)
 		return;
 
 	deferredTriggerInvokeEvents(false);
 
-	MemoryContextDelete(deftrig_cxt);
-	deftrig_cxt = NULL;
+	deferredTriggers = NULL;
 }
 
 
@@ -2136,11 +2135,13 @@ DeferredTriggerAbortXact(void)
 	/*
 	 * Ignore call if we aren't in a transaction.
 	 */
-	if (deftrig_cxt == NULL)
-		return;
+	if (deferredTriggers == NULL)
+			return;
 
-	MemoryContextDelete(deftrig_cxt);
-	deftrig_cxt = NULL;
+	/*
+	 * Forget everything we know about deferred triggers.
+	 */
+	deferredTriggers = NULL;
 }
 
 
@@ -2158,7 +2159,7 @@ DeferredTriggerSetState(ConstraintsSetStmt *stmt)
 	/*
 	 * Ignore call if we aren't in a transaction.
 	 */
-	if (deftrig_cxt == NULL)
+	if (deferredTriggers == NULL)
 		return;
 
 	/*
@@ -2170,7 +2171,7 @@ DeferredTriggerSetState(ConstraintsSetStmt *stmt)
 		 * Drop all per-transaction information about individual trigger
 		 * states.
 		 */
-		l = deftrig_trigstates;
+		l = deferredTriggers->deftrig_trigstates;
 		while (l != NIL)
 		{
 			List	   *next = lnext(l);
@@ -2179,13 +2180,13 @@ DeferredTriggerSetState(ConstraintsSetStmt *stmt)
 			pfree(l);
 			l = next;
 		}
-		deftrig_trigstates = NIL;
+		deferredTriggers->deftrig_trigstates = NIL;
 
 		/*
 		 * Set the per-transaction ALL state to known.
 		 */
-		deftrig_all_isset = true;
-		deftrig_all_isdeferred = stmt->deferred;
+		deferredTriggers->deftrig_all_isset = true;
+		deferredTriggers->deftrig_all_isdeferred = stmt->deferred;
 	}
 	else
 	{
@@ -2267,12 +2268,12 @@ DeferredTriggerSetState(ConstraintsSetStmt *stmt)
 		 * Inside of a transaction block set the trigger states of
 		 * individual triggers on transaction level.
 		 */
-		oldcxt = MemoryContextSwitchTo(deftrig_cxt);
+		oldcxt = MemoryContextSwitchTo(deferredTriggers->deftrig_cxt);
 
 		foreach(l, loid)
 		{
 			found = false;
-			foreach(ls, deftrig_trigstates)
+			foreach(ls, deferredTriggers->deftrig_trigstates)
 			{
 				state = (DeferredTriggerStatus) lfirst(ls);
 				if (state->dts_tgoid == lfirsto(l))
@@ -2289,8 +2290,8 @@ DeferredTriggerSetState(ConstraintsSetStmt *stmt)
 				state->dts_tgoid = lfirsto(l);
 				state->dts_tgisdeferred = stmt->deferred;
 
-				deftrig_trigstates =
-					lappend(deftrig_trigstates, state);
+				deferredTriggers->deftrig_trigstates =
+					lappend(deferredTriggers->deftrig_trigstates, state);
 			}
 		}
 
@@ -2308,7 +2309,7 @@ DeferredTriggerSetState(ConstraintsSetStmt *stmt)
 	 * tail pointer to make it rescan the entire list, in case some deferred
 	 * events are now immediately invokable.
 	 */
-	deftrig_events_imm = NULL;
+	deferredTriggers->deftrig_events_imm = NULL;
 }
 
 
@@ -2337,7 +2338,7 @@ DeferredTriggerSaveEvent(ResultRelInfo *relinfo, int event, bool row_trigger,
 	ItemPointerData oldctid;
 	ItemPointerData newctid;
 
-	if (deftrig_cxt == NULL)
+	if (deferredTriggers == NULL)
 		elog(ERROR,
 			 "DeferredTriggerSaveEvent() called outside of transaction");
 
@@ -2387,7 +2388,7 @@ DeferredTriggerSaveEvent(ResultRelInfo *relinfo, int event, bool row_trigger,
 	/*
 	 * Create a new event
 	 */
-	oldcxt = MemoryContextSwitchTo(deftrig_cxt);
+	oldcxt = MemoryContextSwitchTo(deferredTriggers->deftrig_cxt);
 
 	new_size = offsetof(DeferredTriggerEventData, dte_item[0]) +
 		n_enabled_triggers * sizeof(DeferredTriggerEventItem);