*** pgsql/src/backend/executor/execAmi.c	2009/01/01 17:23:41	1.103
--- pgsql/src/backend/executor/execAmi.c	2009/09/12 22:12:03	1.104
***************
*** 6,12 ****
   * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
!  *	$PostgreSQL: pgsql/src/backend/executor/execAmi.c,v 1.102 2008/12/28 18:53:55 tgl Exp $
   *
   *-------------------------------------------------------------------------
   */
--- 6,12 ----
   * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
!  *	$PostgreSQL: pgsql/src/backend/executor/execAmi.c,v 1.103 2009/01/01 17:23:41 momjian Exp $
   *
   *-------------------------------------------------------------------------
   */
*************** IndexSupportsBackwardScan(Oid indexid)
*** 496,498 ****
--- 496,525 ----
  
  	return result;
  }
+ 
+ /*
+  * ExecMaterializesOutput - does a plan type materialize its output?
+  *
+  * Returns true if the plan node type is one that automatically materializes
+  * its output (typically by keeping it in a tuplestore).  For such plans,
+  * a rescan without any parameter change will have zero startup cost and
+  * very low per-tuple cost.
+  */
+ bool
+ ExecMaterializesOutput(NodeTag plantype)
+ {
+ 	switch (plantype)
+ 	{
+ 		case T_Material:
+ 		case T_FunctionScan:
+ 		case T_CteScan:
+ 		case T_WorkTableScan:
+ 		case T_Sort:
+ 			return true;
+ 
+ 		default:
+ 			break;
+ 	}
+ 
+ 	return false;
+ }