Arrange to copy relcache's trigdesc structure at the start of any

query that uses it.  This ensures that triggers will be applied consistently
throughout a query even if someone commits changes to the relation's
pg_class.reltriggers field meanwhile.  Per crash report from Laurette Cisneros.
While at it, simplify memory management in relcache.c, which no longer
needs the old hack to try to keep trigger info in the same place over
a relcache entry rebuild.  (Should try to fix rd_att and rewrite-rule
access similarly, someday.)  And make RelationBuildTriggers simpler and
more robust by making it build the trigdesc in working memory and then
CopyTriggerDesc() into cache memory.

1 files changed, 162 insertions, 43 deletions

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 4af8a9f9cdc..b404bc3dc51 100644
--- a/src/backend/commands/trigger.c
+++ b/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 1.134 2002/10/03 21:06:23 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.135 2002/10/14 16:51:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -49,7 +49,7 @@ static HeapTuple ExecCallTriggerFunc(TriggerData *trigdata,
 static void DeferredTriggerSaveEvent(ResultRelInfo *relinfo, int event,
 						 HeapTuple oldtup, HeapTuple newtup);
 static void DeferredTriggerExecute(DeferredTriggerEvent event, int itemno,
-					   Relation rel, FmgrInfo *finfo,
+					   Relation rel, TriggerDesc *trigdesc, FmgrInfo *finfo,
 					   MemoryContext per_tuple_context);
 
 
@@ -680,9 +680,12 @@ renametrig(Oid relid,
 /*
  * Build trigger data to attach to the given relcache entry.
  *
- * Note that trigger data must be allocated in CacheMemoryContext
- * to ensure it survives as long as the relcache entry.  But we
- * are probably running in a less long-lived working context.
+ * Note that trigger data attached to a relcache entry must be stored in
+ * CacheMemoryContext to ensure it survives as long as the relcache entry.
+ * But we should be running in a less long-lived working context.  To avoid
+ * leaking cache memory if this routine fails partway through, we build a
+ * temporary TriggerDesc in working memory and then copy the completed
+ * structure into cache memory.
  */
 void
 RelationBuildTriggers(Relation relation)
@@ -695,9 +698,11 @@ RelationBuildTriggers(Relation relation)
 	ScanKeyData skey;
 	SysScanDesc tgscan;
 	HeapTuple	htup;
+	MemoryContext oldContext;
+
+	Assert(ntrigs > 0);			/* else I should not have been called */
 
-	triggers = (Trigger *) MemoryContextAlloc(CacheMemoryContext,
-											  ntrigs * sizeof(Trigger));
+	triggers = (Trigger *) palloc(ntrigs * sizeof(Trigger));
 
 	/*
 	 * Note: since we scan the triggers using TriggerRelidNameIndex, we
@@ -726,9 +731,8 @@ RelationBuildTriggers(Relation relation)
 		build = &(triggers[found]);
 
 		build->tgoid = HeapTupleGetOid(htup);
-		build->tgname = MemoryContextStrdup(CacheMemoryContext,
-							 DatumGetCString(DirectFunctionCall1(nameout,
-									NameGetDatum(&pg_trigger->tgname))));
+		build->tgname = DatumGetCString(DirectFunctionCall1(nameout,
+									NameGetDatum(&pg_trigger->tgname)));
 		build->tgfoid = pg_trigger->tgfoid;
 		build->tgtype = pg_trigger->tgtype;
 		build->tgenabled = pg_trigger->tgenabled;
@@ -753,13 +757,10 @@ RelationBuildTriggers(Relation relation)
 				elog(ERROR, "RelationBuildTriggers: tgargs IS NULL for rel %s",
 					 RelationGetRelationName(relation));
 			p = (char *) VARDATA(val);
-			build->tgargs = (char **)
-				MemoryContextAlloc(CacheMemoryContext,
-								   build->tgnargs * sizeof(char *));
+			build->tgargs = (char **) palloc(build->tgnargs * sizeof(char *));
 			for (i = 0; i < build->tgnargs; i++)
 			{
-				build->tgargs[i] = MemoryContextStrdup(CacheMemoryContext,
-													   p);
+				build->tgargs[i] = pstrdup(p);
 				p += strlen(p) + 1;
 			}
 		}
@@ -778,18 +779,30 @@ RelationBuildTriggers(Relation relation)
 			 RelationGetRelationName(relation));
 
 	/* Build trigdesc */
-	trigdesc = (TriggerDesc *) MemoryContextAlloc(CacheMemoryContext,
-												  sizeof(TriggerDesc));
+	trigdesc = (TriggerDesc *) palloc(sizeof(TriggerDesc));
 	MemSet(trigdesc, 0, sizeof(TriggerDesc));
 	trigdesc->triggers = triggers;
 	trigdesc->numtriggers = ntrigs;
 	for (found = 0; found < ntrigs; found++)
 		InsertTrigger(trigdesc, &(triggers[found]), found);
 
-	relation->trigdesc = trigdesc;
+	/* Copy completed trigdesc into cache storage */
+	oldContext = MemoryContextSwitchTo(CacheMemoryContext);
+	relation->trigdesc = CopyTriggerDesc(trigdesc);
+	MemoryContextSwitchTo(oldContext);
+
+	/* Release working memory */
+	FreeTriggerDesc(trigdesc);
 }
 
-/* Insert the given trigger into the appropriate index list(s) for it */
+/*
+ * Insert the given trigger into the appropriate index list(s) for it
+ *
+ * To simplify storage management, we allocate each index list at the max
+ * possible size (trigdesc->numtriggers) if it's used at all.  This does
+ * not waste space permanently since we're only building a temporary
+ * trigdesc at this point.
+ */
 static void
 InsertTrigger(TriggerDesc *trigdesc, Trigger *trigger, int indx)
 {
@@ -830,11 +843,7 @@ InsertTrigger(TriggerDesc *trigdesc, Trigger *trigger, int indx)
 	{
 		tp = &(t[TRIGGER_EVENT_INSERT]);
 		if (*tp == NULL)
-			*tp = (int *) MemoryContextAlloc(CacheMemoryContext,
-											 sizeof(int));
-		else
-			*tp = (int *) repalloc(*tp, (n[TRIGGER_EVENT_INSERT] + 1) *
-								   sizeof(int));
+			*tp = (int *) palloc(trigdesc->numtriggers * sizeof(int));
 		(*tp)[n[TRIGGER_EVENT_INSERT]] = indx;
 		(n[TRIGGER_EVENT_INSERT])++;
 	}
@@ -843,11 +852,7 @@ InsertTrigger(TriggerDesc *trigdesc, Trigger *trigger, int indx)
 	{
 		tp = &(t[TRIGGER_EVENT_DELETE]);
 		if (*tp == NULL)
-			*tp = (int *) MemoryContextAlloc(CacheMemoryContext,
-											 sizeof(int));
-		else
-			*tp = (int *) repalloc(*tp, (n[TRIGGER_EVENT_DELETE] + 1) *
-								   sizeof(int));
+			*tp = (int *) palloc(trigdesc->numtriggers * sizeof(int));
 		(*tp)[n[TRIGGER_EVENT_DELETE]] = indx;
 		(n[TRIGGER_EVENT_DELETE])++;
 	}
@@ -856,16 +861,113 @@ InsertTrigger(TriggerDesc *trigdesc, Trigger *trigger, int indx)
 	{
 		tp = &(t[TRIGGER_EVENT_UPDATE]);
 		if (*tp == NULL)
-			*tp = (int *) MemoryContextAlloc(CacheMemoryContext,
-											 sizeof(int));
-		else
-			*tp = (int *) repalloc(*tp, (n[TRIGGER_EVENT_UPDATE] + 1) *
-								   sizeof(int));
+			*tp = (int *) palloc(trigdesc->numtriggers * sizeof(int));
 		(*tp)[n[TRIGGER_EVENT_UPDATE]] = indx;
 		(n[TRIGGER_EVENT_UPDATE])++;
 	}
 }
 
+/*
+ * Copy a TriggerDesc data structure.
+ *
+ * The copy is allocated in the current memory context.
+ */
+TriggerDesc *
+CopyTriggerDesc(TriggerDesc *trigdesc)
+{
+	TriggerDesc *newdesc;
+	uint16	   *n;
+	int		  **t,
+			   *tnew;
+	Trigger    *trigger;
+	int			i;
+
+	if (trigdesc == NULL || trigdesc->numtriggers <= 0)
+		return NULL;
+
+	newdesc = (TriggerDesc *) palloc(sizeof(TriggerDesc));
+	memcpy(newdesc, trigdesc, sizeof(TriggerDesc));
+
+	trigger = (Trigger *) palloc(trigdesc->numtriggers * sizeof(Trigger));
+	memcpy(trigger, trigdesc->triggers,
+		   trigdesc->numtriggers * sizeof(Trigger));
+	newdesc->triggers = trigger;
+
+	for (i = 0; i < trigdesc->numtriggers; i++)
+	{
+		trigger->tgname = pstrdup(trigger->tgname);
+		if (trigger->tgnargs > 0)
+		{
+			char  **newargs;
+			int16	j;
+
+			newargs = (char **) palloc(trigger->tgnargs * sizeof(char *));
+			for (j = 0; j < trigger->tgnargs; j++)
+				newargs[j] = pstrdup(trigger->tgargs[j]);
+			trigger->tgargs = newargs;
+		}
+		trigger++;
+	}
+
+	n = newdesc->n_before_statement;
+	t = newdesc->tg_before_statement;
+	for (i = 0; i < TRIGGER_NUM_EVENT_CLASSES; i++)
+	{
+		if (n[i] > 0)
+		{
+			tnew = (int *) palloc(n[i] * sizeof(int));
+			memcpy(tnew, t[i], n[i] * sizeof(int));
+			t[i] = tnew;
+		}
+		else
+			t[i] = NULL;
+	}
+	n = newdesc->n_before_row;
+	t = newdesc->tg_before_row;
+	for (i = 0; i < TRIGGER_NUM_EVENT_CLASSES; i++)
+	{
+		if (n[i] > 0)
+		{
+			tnew = (int *) palloc(n[i] * sizeof(int));
+			memcpy(tnew, t[i], n[i] * sizeof(int));
+			t[i] = tnew;
+		}
+		else
+			t[i] = NULL;
+	}
+	n = newdesc->n_after_row;
+	t = newdesc->tg_after_row;
+	for (i = 0; i < TRIGGER_NUM_EVENT_CLASSES; i++)
+	{
+		if (n[i] > 0)
+		{
+			tnew = (int *) palloc(n[i] * sizeof(int));
+			memcpy(tnew, t[i], n[i] * sizeof(int));
+			t[i] = tnew;
+		}
+		else
+			t[i] = NULL;
+	}
+	n = newdesc->n_after_statement;
+	t = newdesc->tg_after_statement;
+	for (i = 0; i < TRIGGER_NUM_EVENT_CLASSES; i++)
+	{
+		if (n[i] > 0)
+		{
+			tnew = (int *) palloc(n[i] * sizeof(int));
+			memcpy(tnew, t[i], n[i] * sizeof(int));
+			t[i] = tnew;
+		}
+		else
+			t[i] = NULL;
+	}
+
+	return newdesc;
+}
+
+/*
+ * Free a TriggerDesc data structure.
+ */
 void
 FreeTriggerDesc(TriggerDesc *trigdesc)
 {
@@ -909,6 +1011,10 @@ FreeTriggerDesc(TriggerDesc *trigdesc)
 	pfree(trigdesc);
 }
 
+/*
+ * Compare two TriggerDesc structures for logical equality.
+ */
+#ifdef NOT_USED
 bool
 equalTriggerDescs(TriggerDesc *trigdesc1, TriggerDesc *trigdesc2)
 {
@@ -966,6 +1072,7 @@ equalTriggerDescs(TriggerDesc *trigdesc1, TriggerDesc *trigdesc2)
 		return false;
 	return true;
 }
+#endif /* NOT_USED */
 
 /*
  * Call a trigger function.
@@ -1455,17 +1562,17 @@ deferredTriggerAddEvent(DeferredTriggerEvent event)
  *	event: event currently being fired.
  *	itemno: item within event currently being fired.
  *	rel: open relation for event.
- *	finfo: array of fmgr lookup cache entries (one per trigger of relation).
+ *	trigdesc: working copy of rel's trigger info.
+ *	finfo: array of fmgr lookup cache entries (one per trigger in trigdesc).
  *	per_tuple_context: memory context to call trigger function in.
  * ----------
  */
 static void
 DeferredTriggerExecute(DeferredTriggerEvent event, int itemno,
-					   Relation rel, FmgrInfo *finfo,
+					   Relation rel, TriggerDesc *trigdesc, FmgrInfo *finfo,
 					   MemoryContext per_tuple_context)
 {
 	Oid			tgoid = event->dte_item[itemno].dti_tgoid;
-	TriggerDesc *trigdesc = rel->trigdesc;
 	TriggerData LocTriggerData;
 	HeapTupleData oldtuple;
 	HeapTupleData newtuple;
@@ -1530,7 +1637,7 @@ DeferredTriggerExecute(DeferredTriggerEvent event, int itemno,
 	}
 
 	/*
-	 * Call the trigger and throw away an eventually returned updated
+	 * Call the trigger and throw away any eventually returned updated
 	 * tuple.
 	 */
 	rettuple = ExecCallTriggerFunc(&LocTriggerData,
@@ -1569,6 +1676,7 @@ deferredTriggerInvokeEvents(bool immediate_only)
 				prev_event = NULL;
 	MemoryContext per_tuple_context;
 	Relation	rel = NULL;
+	TriggerDesc *trigdesc = NULL;
 	FmgrInfo   *finfo = NULL;
 
 	/*
@@ -1637,6 +1745,7 @@ deferredTriggerInvokeEvents(bool immediate_only)
 				{
 					if (rel)
 						heap_close(rel, NoLock);
+					FreeTriggerDesc(trigdesc);
 					if (finfo)
 						pfree(finfo);
 
@@ -1647,16 +1756,25 @@ deferredTriggerInvokeEvents(bool immediate_only)
 					rel = heap_open(event->dte_relid, NoLock);
 
 					/*
-					 * Allocate space to cache fmgr lookup info for
-					 * triggers of this relation.
+					 * Copy relation's trigger info so that we have a stable
+					 * copy no matter what the called triggers do.
+					 */
+					trigdesc = CopyTriggerDesc(rel->trigdesc);
+
+					if (trigdesc == NULL)
+						elog(ERROR, "deferredTriggerInvokeEvents: relation %u has no triggers",
+							 event->dte_relid);
+
+					/*
+					 * Allocate space to cache fmgr lookup info for triggers.
 					 */
 					finfo = (FmgrInfo *)
-						palloc(rel->trigdesc->numtriggers * sizeof(FmgrInfo));
+						palloc(trigdesc->numtriggers * sizeof(FmgrInfo));
 					MemSet(finfo, 0,
-						   rel->trigdesc->numtriggers * sizeof(FmgrInfo));
+						   trigdesc->numtriggers * sizeof(FmgrInfo));
 				}
 
-				DeferredTriggerExecute(event, i, rel, finfo,
+				DeferredTriggerExecute(event, i, rel, trigdesc, finfo,
 									   per_tuple_context);
 
 				event->dte_item[i].dti_state |= TRIGGER_DEFERRED_DONE;
@@ -1708,6 +1826,7 @@ deferredTriggerInvokeEvents(bool immediate_only)
 	/* Release working resources */
 	if (rel)
 		heap_close(rel, NoLock);
+	FreeTriggerDesc(trigdesc);
 	if (finfo)
 		pfree(finfo);
 	MemoryContextDelete(per_tuple_context);