Oops, in the previous fix to prevent a cursor that's being used in a FOR

loop from being dropped, I missed subtransaction cleanup. Pinned portals
must be dropped at subtransaction cleanup just as they are at main
transaction cleanup.

Per bug #5556 by Robert Walker. Backpatch to 8.0, 7.4 didn't have
subtransactions.

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 1.120 2010/07/06 19:18:59 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.121 2010/07/13 09:02:30 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -379,6 +379,9 @@ PortalCreateHoldStore(Portal portal)
 /*
  * PinPortal
  *		Protect a portal from dropping.
+ *
+ * A pinned portal is still unpinned and dropped at transaction or
+ * subtransaction abort.
  */
 void
 PinPortal(Portal portal)
@@ -902,6 +905,14 @@ AtSubCleanup_Portals(SubTransactionId mySubid)
 		if (portal->createSubid != mySubid)
 			continue;
 
+		/*
+		 * If a portal is still pinned, forcibly unpin it. PortalDrop will not
+		 * let us drop the portal otherwise. Whoever pinned the portal was
+		 * interrupted by the abort too and won't try to use it anymore.
+		 */
+		if (portal->portalPinned)
+			portal->portalPinned = false;
+
 		/* Zap it. */
 		PortalDrop(portal, false);
 	}