Index: src/backend/catalog/heap.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/catalog/heap.c,v
retrieving revision 1.357
diff -c -r1.357 heap.c
*** src/backend/catalog/heap.c	2 Aug 2009 22:14:52 -0000	1.357
--- src/backend/catalog/heap.c	6 Aug 2009 06:15:05 -0000
***************
*** 2342,2359 ****
  	{
  		Oid			rid = lfirst_oid(cell);
  		Relation	rel;
- 		Oid			toastrelid;
  
  		rel = heap_open(rid, AccessExclusiveLock);
  		relations = lappend(relations, rel);
- 
- 		/* If there is a toast table, add it to the list too */
- 		toastrelid = rel->rd_rel->reltoastrelid;
- 		if (OidIsValid(toastrelid))
- 		{
- 			rel = heap_open(toastrelid, AccessExclusiveLock);
- 			relations = lappend(relations, rel);
- 		}
  	}
  
  	/* Don't allow truncate on tables that are referenced by foreign keys */
--- 2342,2350 ----
***************
*** 2364,2383 ****
  	{
  		Relation	rel = lfirst(cell);
  
! 		/* Truncate the actual file (and discard buffers) */
! 		RelationTruncate(rel, 0);
  
! 		/* If this relation has indexes, truncate the indexes too */
! 		RelationTruncateIndexes(rel);
! 
! 		/*
! 		 * Close the relation, but keep exclusive lock on it until commit.
! 		 */
  		heap_close(rel, NoLock);
  	}
  }
  
  /*
   * heap_truncate_check_FKs
   *		Check for foreign keys referencing a list of relations that
   *		are to be truncated, and raise error if there are any
--- 2355,2402 ----
  	{
  		Relation	rel = lfirst(cell);
  
! 		/* Truncate the relation */
! 		heap_truncate_one_rel(rel);
  
! 		/* Close the relation, but keep exclusive lock on it until commit */
  		heap_close(rel, NoLock);
  	}
  }
  
  /*
+  *	 heap_truncate_one_rel
+  *
+  *	 This routine deletes all data within the specified relation.
+  *
+  * This is not transaction-safe, because the truncation is done immediately
+  * and cannot be rolled back later.  Caller is responsible for having
+  * checked permissions etc, and must have obtained AccessExclusiveLock.
+  */
+ void
+ heap_truncate_one_rel(Relation rel)
+ {
+ 	Oid			toastrelid;
+ 
+ 	/* Truncate the actual file (and discard buffers) */
+ 	RelationTruncate(rel, 0);
+ 
+ 	/* If the relation has indexes, truncate the indexes too */
+ 	RelationTruncateIndexes(rel);
+ 
+ 	/* If there is a toast table, truncate that too */
+ 	toastrelid = rel->rd_rel->reltoastrelid;
+ 	if (OidIsValid(toastrelid))
+ 	{
+ 		Relation	toastrel = heap_open(toastrelid, AccessExclusiveLock);
+ 
+ 		RelationTruncate(toastrel, 0);
+ 		RelationTruncateIndexes(toastrel);
+ 		/* keep the lock... */
+ 		heap_close(toastrel, NoLock);
+ 	}
+ }
+ 
+ /*
   * heap_truncate_check_FKs
   *		Check for foreign keys referencing a list of relations that
   *		are to be truncated, and raise error if there are any
Index: src/backend/commands/tablecmds.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v
retrieving revision 1.295
diff -c -r1.295 tablecmds.c
*** src/backend/commands/tablecmds.c	2 Aug 2009 22:14:52 -0000	1.295
--- src/backend/commands/tablecmds.c	6 Aug 2009 06:15:06 -0000
***************
*** 775,780 ****
--- 775,781 ----
  	EState	   *estate;
  	ResultRelInfo *resultRelInfos;
  	ResultRelInfo *resultRelInfo;
+ 	SubTransactionId mySubid;
  	ListCell   *cell;
  
  	/*
***************
*** 944,979 ****
  	/*
  	 * OK, truncate each table.
  	 */
  	foreach(cell, rels)
  	{
  		Relation	rel = (Relation) lfirst(cell);
- 		Oid			heap_relid;
- 		Oid			toast_relid;
  
  		/*
! 		 * Create a new empty storage file for the relation, and assign it as
! 		 * the relfilenode value.	The old storage file is scheduled for
! 		 * deletion at commit.
  		 */
! 		setNewRelfilenode(rel, RecentXmin);
! 
! 		heap_relid = RelationGetRelid(rel);
! 		toast_relid = rel->rd_rel->reltoastrelid;
! 
! 		/*
! 		 * The same for the toast table, if any.
! 		 */
! 		if (OidIsValid(toast_relid))
  		{
! 			rel = relation_open(toast_relid, AccessExclusiveLock);
! 			setNewRelfilenode(rel, RecentXmin);
! 			heap_close(rel, NoLock);
  		}
  
! 		/*
! 		 * Reconstruct the indexes to match, and we're done.
! 		 */
! 		reindex_relation(heap_relid, true);
  	}
  
  	/*
--- 945,1002 ----
  	/*
  	 * OK, truncate each table.
  	 */
+ 	mySubid = GetCurrentSubTransactionId();
+ 
  	foreach(cell, rels)
  	{
  		Relation	rel = (Relation) lfirst(cell);
  
  		/*
! 		 * Normally, we need a transaction-safe truncation here.  However,
! 		 * if the table was either created in the current (sub)transaction
! 		 * or has a new relfilenode in the current (sub)transaction, then
! 		 * we can just truncate it in-place, because a rollback would
! 		 * cause the whole table or the current physical file to be
! 		 * thrown away anyway.
  		 */
! 		if (rel->rd_createSubid == mySubid ||
! 			rel->rd_newRelfilenodeSubid == mySubid)
  		{
! 			/* Immediate, non-rollbackable truncation is OK */
! 			heap_truncate_one_rel(rel);
  		}
+ 		else
+ 		{
+ 			Oid			heap_relid;
+ 			Oid			toast_relid;
  
! 			/*
! 			 * Need the full transaction-safe pushups.
! 			 *
! 			 * Create a new empty storage file for the relation, and assign it
! 			 * as the relfilenode value. The old storage file is scheduled for
! 			 * deletion at commit.
! 			 */
! 			setNewRelfilenode(rel, RecentXmin);
! 
! 			heap_relid = RelationGetRelid(rel);
! 			toast_relid = rel->rd_rel->reltoastrelid;
! 
! 			/*
! 			 * The same for the toast table, if any.
! 			 */
! 			if (OidIsValid(toast_relid))
! 			{
! 				rel = relation_open(toast_relid, AccessExclusiveLock);
! 				setNewRelfilenode(rel, RecentXmin);
! 				heap_close(rel, NoLock);
! 			}
! 
! 			/*
! 			 * Reconstruct the indexes to match, and we're done.
! 			 */
! 			reindex_relation(heap_relid, true);
! 		}
  	}
  
  	/*
Index: src/include/catalog/heap.h
===================================================================
RCS file: /cvsroot/pgsql/src/include/catalog/heap.h,v
retrieving revision 1.91
diff -c -r1.91 heap.h
*** src/include/catalog/heap.h	11 Jun 2009 14:49:09 -0000	1.91
--- src/include/catalog/heap.h	6 Aug 2009 06:15:06 -0000
***************
*** 62,67 ****
--- 62,69 ----
  
  extern void heap_truncate(List *relids);
  
+ extern void heap_truncate_one_rel(Relation rel);
+ 
  extern void heap_truncate_check_FKs(List *relations, bool tempTables);
  
  extern List *heap_truncate_find_FKs(List *relationIds);