Force READY portals into FAILED state when a transaction or subtransaction

is aborted, if they were created within the failed xact.  This prevents
ExecutorEnd from being run on them, which is a good idea because they may
contain references to tables or other objects that no longer exist.
In particular this is hazardous when auto_explain is active, but it's
really rather surprising that nobody has seen an issue with this before.
I'm back-patching this to 8.4, since that's the first version that contains
auto_explain or an ExecutorEnd hook, but I wonder whether we shouldn't
back-patch further.

src/backend/utils/mmgr/portalmem.c

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.116 2010/01/18 02:30:25 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.117 2010/02/18 03:06:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -668,6 +668,7 @@ AtAbort_Portals(void)
 	{
 		Portal		portal = hentry->portal;
 
+		/* Any portal that was actually running has to be considered broken */
 		if (portal->status == PORTAL_ACTIVE)
 			portal->status = PORTAL_FAILED;
 
@@ -677,6 +678,15 @@ AtAbort_Portals(void)
 		if (portal->createSubid == InvalidSubTransactionId)
 			continue;
 
+		/*
+		 * If it was created in the current transaction, we can't do normal
+		 * shutdown on a READY portal either; it might refer to objects
+		 * created in the failed transaction.  See comments in
+		 * AtSubAbort_Portals.
+		 */
+		if (portal->status == PORTAL_READY)
+			portal->status = PORTAL_FAILED;
+
 		/* let portalcmds.c clean up the state it knows about */
 		if (PointerIsValid(portal->cleanup))
 		{
@@ -789,61 +799,41 @@ AtSubAbort_Portals(SubTransactionId mySubid,
 			continue;
 
 		/*
-		 * Force any active portals of my own transaction into FAILED state.
-		 * This is mostly to ensure that a portal running a FETCH will go
-		 * FAILED if the underlying cursor fails.  (Note we do NOT want to do
-		 * this to upper-level portals, since they may be able to continue.)
-		 *
-		 * This is only needed to dodge the sanity check in PortalDrop.
+		 * Force any live portals of my own subtransaction into FAILED state.
+		 * We have to do this because they might refer to objects created or
+		 * changed in the failed subtransaction, leading to crashes if
+		 * execution is resumed, or even if we just try to run ExecutorEnd.
+		 * (Note we do NOT do this to upper-level portals, since they cannot
+		 * have such references and hence may be able to continue.)
 		 */
-		if (portal->status == PORTAL_ACTIVE)
+		if (portal->status == PORTAL_READY ||
+			portal->status == PORTAL_ACTIVE)
 			portal->status = PORTAL_FAILED;
 
-		/*
-		 * If the portal is READY then allow it to survive into the parent
-		 * transaction; otherwise shut it down.
-		 *
-		 * Currently, we can't actually support that because the portal's
-		 * query might refer to objects created or changed in the failed
-		 * subtransaction, leading to crashes if execution is resumed. So,
-		 * even READY portals are deleted.	It would be nice to detect whether
-		 * the query actually depends on any such object, instead.
-		 */
-#ifdef NOT_USED
-		if (portal->status == PORTAL_READY)
+		/* let portalcmds.c clean up the state it knows about */
+		if (PointerIsValid(portal->cleanup))
 		{
-			portal->createSubid = parentSubid;
-			if (portal->resowner)
-				ResourceOwnerNewParent(portal->resowner, parentXactOwner);
+			(*portal->cleanup) (portal);
+			portal->cleanup = NULL;
 		}
-		else
-#endif
-		{
-			/* let portalcmds.c clean up the state it knows about */
-			if (PointerIsValid(portal->cleanup))
-			{
-				(*portal->cleanup) (portal);
-				portal->cleanup = NULL;
-			}
 
-			/* drop cached plan reference, if any */
-			PortalReleaseCachedPlan(portal);
+		/* drop cached plan reference, if any */
+		PortalReleaseCachedPlan(portal);
 
-			/*
-			 * Any resources belonging to the portal will be released in the
-			 * upcoming transaction-wide cleanup; they will be gone before we
-			 * run PortalDrop.
-			 */
-			portal->resowner = NULL;
+		/*
+		 * Any resources belonging to the portal will be released in the
+		 * upcoming transaction-wide cleanup; they will be gone before we
+		 * run PortalDrop.
+		 */
+		portal->resowner = NULL;
 
-			/*
-			 * Although we can't delete the portal data structure proper, we
-			 * can release any memory in subsidiary contexts, such as executor
-			 * state.  The cleanup hook was the last thing that might have
-			 * needed data there.
-			 */
-			MemoryContextDeleteChildren(PortalGetHeapMemory(portal));
-		}
+		/*
+		 * Although we can't delete the portal data structure proper, we
+		 * can release any memory in subsidiary contexts, such as executor
+		 * state.  The cleanup hook was the last thing that might have
+		 * needed data there.
+		 */
+		MemoryContextDeleteChildren(PortalGetHeapMemory(portal));
 	}
 }