When building a bitmap scan, must copy the bitmapqualorig expression tree

to avoid sharing substructure with the lower-level indexquals.  This is
currently only an issue if there are SubPlans in the indexquals, which is
uncommon but not impossible --- see bug #2218 reported by Nicholas Vinen.
We use the same kluge for indexqual vs indexqualorig in the index scans
themselves ... would be nice to clean this up someday.

src/backend/optimizer/plan/createplan.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.206 2006/01/25 20:29:23 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.207 2006/01/29 18:55:48 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -963,6 +963,12 @@ create_bitmap_scan_plan(PlannerInfo *root,
 	 */
 	bitmapqualorig = list_difference_ptr(bitmapqualorig, qpqual);
 
+	/*
+	 * Copy the finished bitmapqualorig to make sure we have an independent
+	 * copy --- needed in case there are subplans in the index quals
+	 */
+	bitmapqualorig = copyObject(bitmapqualorig);
+
 	/* Finally ready to build the plan node */
 	scan_plan = make_bitmap_heapscan(tlist,
 									 qpqual,