Index: src/backend/access/heap/heapam.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/access/heap/heapam.c,v
retrieving revision 1.222.2.1
diff -c -r1.222.2.1 heapam.c
*** src/backend/access/heap/heapam.c	4 Feb 2007 20:00:49 -0000	1.222.2.1
--- src/backend/access/heap/heapam.c	4 Mar 2008 12:42:05 -0000
***************
*** 699,704 ****
--- 699,708 ----
  	if (!RelationIsValid(r))
  		elog(ERROR, "could not open relation with OID %u", relationId);
  
+ 	/* Make note that we've accessed a temporary relation. */
+ 	if (r->rd_istemp)
+ 		MyXactAccessedTempRel = true;
+ 
  	return r;
  }
  
***************
*** 741,746 ****
--- 745,755 ----
  	if (!RelationIsValid(r))
  		elog(ERROR, "could not open relation with OID %u", relationId);
  
+ 
+ 	/* Make note that we've accessed a temporary relation. */
+ 	if (r->rd_istemp)
+ 		MyXactAccessedTempRel = true;
+ 
  	return r;
  }
  
***************
*** 785,790 ****
--- 794,803 ----
  	if (!RelationIsValid(r))
  		elog(ERROR, "could not open relation with OID %u", relationId);
  
+ 	/* Make note that we've accessed a temporary relation. */
+ 	if (r->rd_istemp)
+ 		MyXactAccessedTempRel = true;
+ 
  	return r;
  }
  
Index: src/backend/access/transam/xact.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/access/transam/xact.c,v
retrieving revision 1.229.2.3
diff -c -r1.229.2.3 xact.c
*** src/backend/access/transam/xact.c	3 Jan 2008 21:23:45 -0000	1.229.2.3
--- src/backend/access/transam/xact.c	4 Mar 2008 12:34:43 -0000
***************
*** 174,179 ****
--- 174,185 ----
  static char *prepareGID;
  
  /*
+  * MyXactAccessedTempRel is set when a temporary relation is accessed. We
+  * don't allow PREPARE TRANSACTION in that case.
+  */
+ bool MyXactAccessedTempRel = false;
+ 
+ /*
   * Private context for transaction-abort work --- we reserve space for this
   * at startup to ensure that AbortTransaction and AbortSubTransaction can work
   * when we've run out of memory.
***************
*** 1389,1394 ****
--- 1395,1401 ----
  	FreeXactSnapshot();
  	XactIsoLevel = DefaultXactIsoLevel;
  	XactReadOnly = DefaultXactReadOnly;
+ 	MyXactAccessedTempRel = false;
  
  	/*
  	 * reinitialize within-transaction counters
***************
*** 1715,1720 ****
--- 1722,1753 ----
  
  	/* NOTIFY and flatfiles will be handled below */
  
+ 	/*
+ 	 * Don't allow PREPARE TRANSACTION if we've accessed a temporary table
+ 	 * in this transaction. It's not clear what should happen if a prepared
+ 	 * transaction holds a lock on a temp table, and the original backend
+ 	 * exits and deletes the file, for example. Also, if a temp table is
+ 	 * dropped, we have no way of flushing temp buffers from the backend-
+ 	 * private temp buffer cache of the original backend at COMMIT PREPARED,
+ 	 * since it can be executed in a different backend.
+ 	 *
+ 	 * We need to check this after executing any ON COMMIT actions, because
+ 	 * they might still access a temp relation.
+ 	 *
+ 	 * It would be nice to relax this restriction so that you could operate on
+ 	 * ON COMMIT DELETE ROWS temp tables, or on one created and dropped in the
+ 	 * same transaction, by releasing the locks on it at PREPARE TRANSACTION,
+ 	 * instead of COMMIT PREPARED as usual. Another case we could allow is if
+ 	 * the access to the temp relation happened in a subtransaction that later
+ 	 * rolled back. MyXactAccessedTempRel would needto be per-subxact to track
+ 	 * that, but it doesn't seem worth the effort given how narrow the use
+ 	 * case for that is.
+ 	 */
+ 	if (MyXactAccessedTempRel)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ 				 errmsg("cannot PREPARE a transaction that has operated on temporary tables")));
+ 
  	/* Prevent cancel/die interrupt while cleaning up */
  	HOLD_INTERRUPTS();
  
Index: src/backend/storage/lmgr/lmgr.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/storage/lmgr/lmgr.c,v
retrieving revision 1.89
diff -c -r1.89 lmgr.c
*** src/backend/storage/lmgr/lmgr.c	4 Oct 2006 00:29:57 -0000	1.89
--- src/backend/storage/lmgr/lmgr.c	4 Mar 2008 12:35:00 -0000
***************
*** 598,637 ****
  
  	LockRelease(&tag, lockmode, false);
  }
- 
- 
- /*
-  * LockTagIsTemp
-  *		Determine whether a locktag is for a lock on a temporary object
-  *
-  * We need this because 2PC cannot deal with temp objects
-  */
- bool
- LockTagIsTemp(const LOCKTAG *tag)
- {
- 	switch (tag->locktag_type)
- 	{
- 		case LOCKTAG_RELATION:
- 		case LOCKTAG_RELATION_EXTEND:
- 		case LOCKTAG_PAGE:
- 		case LOCKTAG_TUPLE:
- 			/* check for lock on a temp relation */
- 			/* field1 is dboid, field2 is reloid for all of these */
- 			if ((Oid) tag->locktag_field1 == InvalidOid)
- 				return false;	/* shared, so not temp */
- 			if (isTempNamespace(get_rel_namespace((Oid) tag->locktag_field2)))
- 				return true;
- 			break;
- 		case LOCKTAG_TRANSACTION:
- 			/* there are no temp transactions */
- 			break;
- 		case LOCKTAG_OBJECT:
- 			/* there are currently no non-table temp objects */
- 			break;
- 		case LOCKTAG_USERLOCK:
- 		case LOCKTAG_ADVISORY:
- 			/* assume these aren't temp */
- 			break;
- 	}
- 	return false;				/* default case */
- }
--- 598,600 ----
Index: src/backend/storage/lmgr/lock.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/storage/lmgr/lock.c,v
retrieving revision 1.174.2.1
diff -c -r1.174.2.1 lock.c
*** src/backend/storage/lmgr/lock.c	2 Feb 2008 22:26:23 -0000	1.174.2.1
--- src/backend/storage/lmgr/lock.c	4 Mar 2008 12:32:30 -0000
***************
*** 1849,1860 ****
  				elog(ERROR, "cannot PREPARE when session locks exist");
  		}
  
- 		/* Can't handle it if the lock is on a temporary object */
- 		if (LockTagIsTemp(&locallock->tag.lock))
- 			ereport(ERROR,
- 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- 					 errmsg("cannot PREPARE a transaction that has operated on temporary tables")));
- 
  		/*
  		 * Create a 2PC record.
  		 */
--- 1849,1854 ----
Index: src/include/access/xact.h
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/include/access/xact.h,v
retrieving revision 1.83
diff -c -r1.83 xact.h
*** src/include/access/xact.h	11 Jul 2006 18:26:11 -0000	1.83
--- src/include/access/xact.h	4 Mar 2008 12:32:30 -0000
***************
*** 41,46 ****
--- 41,48 ----
  extern bool DefaultXactReadOnly;
  extern bool XactReadOnly;
  
+ extern bool MyXactAccessedTempRel;
+ 
  /*
   *	start- and end-of-transaction callbacks for dynamically loaded modules
   */