The following patch cleans up the deferred trigger mechanism. There is

an unneeded memory context and some variables that are not used anymore.
It's pretty trivial and the regression tests pass fine.  There's no
change in functionality, only deletion of unused code.  I left an empty
function because maybe I'll need it for nested transactions.

Alvaro Herrera

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 1.146 2003/03/27 14:33:11 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.147 2003/03/31 20:47:51 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,6 +15,7 @@
 
 #include "access/genam.h"
 #include "access/heapam.h"
+#include "access/xact.h"
 #include "catalog/catalog.h"
 #include "catalog/catname.h"
 #include "catalog/dependency.h"
@@ -1601,14 +1602,12 @@ ltrmark:;
  */
 
 
-/* ----------
- * Internal data to the deferred trigger mechanism is held
- * during entire session in a global context created at startup and
- * over statements/commands in a separate context which
- * is created at transaction start and destroyed at transaction end.
- * ----------
+/*
+ * 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_gcxt = NULL;
+
 static MemoryContext deftrig_cxt = NULL;
 
 /* ----------
@@ -1616,8 +1615,6 @@ static MemoryContext deftrig_cxt = NULL;
  * state IMMEDIATE or DEFERRED.
  * ----------
  */
-static List *deftrig_dfl_trigstates = NIL;
-
 static bool deftrig_all_isset = false;
 static bool deftrig_all_isdeferred = false;
 static List *deftrig_trigstates;
@@ -2017,11 +2014,8 @@ deferredTriggerInvokeEvents(bool immediate_only)
 void
 DeferredTriggerInit(void)
 {
-	deftrig_gcxt = AllocSetContextCreate(TopMemoryContext,
-										 "DeferredTriggerSession",
-										 ALLOCSET_DEFAULT_MINSIZE,
-										 ALLOCSET_DEFAULT_INITSIZE,
-										 ALLOCSET_DEFAULT_MAXSIZE);
+	/* Nothing to do */
+	;
 }
 
 
@@ -2035,26 +2029,18 @@ DeferredTriggerInit(void)
 void
 DeferredTriggerBeginXact(void)
 {
-	MemoryContext oldcxt;
-	List	   *l;
-	DeferredTriggerStatus dflstat;
-	DeferredTriggerStatus stat;
-
 	if (deftrig_cxt != NULL)
 		elog(ERROR,
 		   "DeferredTriggerBeginXact() called while inside transaction");
 
 	/*
-	 * Create the per transaction memory context and copy all states from
-	 * the per session context to here.
+	 * Create the per transaction memory context
 	 */
 	deftrig_cxt = AllocSetContextCreate(TopTransactionContext,
 										"DeferredTriggerXact",
 										ALLOCSET_DEFAULT_MINSIZE,
 										ALLOCSET_DEFAULT_INITSIZE,
 										ALLOCSET_DEFAULT_MAXSIZE);
-	oldcxt = MemoryContextSwitchTo(deftrig_cxt);
-
 	deftrig_all_isset = false;
 
 	/*
@@ -2063,19 +2049,6 @@ DeferredTriggerBeginXact(void)
 	deftrig_all_isdeferred = false;
 
 	deftrig_trigstates = NIL;
-	foreach(l, deftrig_dfl_trigstates)
-	{
-		dflstat = (DeferredTriggerStatus) lfirst(l);
-		stat = (DeferredTriggerStatus)
-			palloc(sizeof(DeferredTriggerStatusData));
-
-		stat->dts_tgoid = dflstat->dts_tgoid;
-		stat->dts_tgisdeferred = dflstat->dts_tgisdeferred;
-
-		deftrig_trigstates = lappend(deftrig_trigstates, stat);
-	}
-
-	MemoryContextSwitchTo(oldcxt);
 
 	deftrig_events = NULL;
 	deftrig_event_tail = NULL;