Back-patch fix for bogus plans involving non-mark/restorable plan

as inner plan of a mergejoin.

src/backend/executor/execAmi.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	$Id: execAmi.c,v 1.46 2000/04/12 17:15:07 momjian Exp $
+ *	$Id: execAmi.c,v 1.46.2.1 2000/09/08 02:11:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -424,7 +424,7 @@ ExecMarkPos(Plan *node)
 {
 	switch (nodeTag(node))
 	{
-			case T_SeqScan:
+		case T_SeqScan:
 			ExecSeqMarkPos((SeqScan *) node);
 			break;
 
@@ -432,6 +432,10 @@ ExecMarkPos(Plan *node)
 			ExecIndexMarkPos((IndexScan *) node);
 			break;
 
+		case T_Material:
+			ExecMaterialMarkPos((Material *) node);
+			break;
+
 		case T_Sort:
 			ExecSortMarkPos((Sort *) node);
 			break;
@@ -458,7 +462,7 @@ ExecRestrPos(Plan *node)
 {
 	switch (nodeTag(node))
 	{
-			case T_SeqScan:
+		case T_SeqScan:
 			ExecSeqRestrPos((SeqScan *) node);
 			return;
 
@@ -466,12 +470,16 @@ ExecRestrPos(Plan *node)
 			ExecIndexRestrPos((IndexScan *) node);
 			return;
 
+		case T_Material:
+			ExecMaterialRestrPos((Material *) node);
+			break;
+
 		case T_Sort:
 			ExecSortRestrPos((Sort *) node);
 			return;
 
 		default:
-			elog(DEBUG, "ExecRestrPos: node type %u not supported", nodeTag(node));
+			elog(ERROR, "ExecRestrPos: node type %u not supported", nodeTag(node));
 			return;
 	}
 }

src/backend/executor/nodeMaterial.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeMaterial.c,v 1.30 2000/03/02 04:06:39 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeMaterial.c,v 1.30.2.1 2000/09/08 02:11:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -352,35 +352,30 @@ ExecMaterialReScan(Material *node, ExprContext *exprCtxt, Plan *parent)
 
 }
 
-#ifdef NOT_USED					/* not used */
 /* ----------------------------------------------------------------
  *		ExecMaterialMarkPos
  * ----------------------------------------------------------------
  */
-List							/* nothing of interest */
+void
-ExecMaterialMarkPos(Material node)
+ExecMaterialMarkPos(Material *node)
 {
-	MaterialState matstate;
+	MaterialState *matstate;
 	HeapScanDesc scan;
 
 	/* ----------------
-	 *	if we haven't materialized yet, just return NIL.
+	 *	if we haven't materialized yet, just return.
 	 * ----------------
 	 */
-	matstate = get_matstate(node);
+	matstate = node->matstate;
-	if (get_mat_Flag(matstate) == false)
+	if (matstate->mat_Flag == false)
-		return NIL;
+		return;
 
 	/* ----------------
-	 *	XXX access methods don't return positions yet so
+	 *	mark the scan position
-	 *		for now we return NIL.	It's possible that
-	 *		they will never return positions for all I know -cim 10/16/89
 	 * ----------------
 	 */
-	scan = get_css_currentScanDesc((CommonScanState) matstate);
+	scan = matstate->csstate.css_currentScanDesc;
 	heap_markpos(scan);
-
-	return NIL;
 }
 
 /* ----------------------------------------------------------------
@@ -388,25 +383,23 @@ ExecMaterialMarkPos(Material node)
  * ----------------------------------------------------------------
  */
 void
-ExecMaterialRestrPos(Material node)
+ExecMaterialRestrPos(Material *node)
 {
-	MaterialState matstate;
+	MaterialState *matstate;
 	HeapScanDesc scan;
 
 	/* ----------------
 	 *	if we haven't materialized yet, just return.
 	 * ----------------
 	 */
-	matstate = get_matstate(node);
+	matstate = node->matstate;
-	if (get_mat_Flag(matstate) == false)
+	if (matstate->mat_Flag == false)
 		return;
 
 	/* ----------------
 	 *	restore the scan to the previously marked position
 	 * ----------------
 	 */
-	scan = get_css_currentScanDesc((CommonScanState) matstate);
+	scan = matstate->csstate.css_currentScanDesc;
 	heap_restrpos(scan);
 }
-
-#endif

src/backend/optimizer/plan/createplan.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.90 2000/05/23 16:56:36 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.90.2.1 2000/09/08 02:11:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -639,6 +639,44 @@ create_mergejoin_node(MergePath *best_path,
 										  best_path->innersortkeys,
 										  inner_node);
 
+	/*
+	 * The executor requires the inner side of a mergejoin to support "mark"
+	 * and "restore" operations.  Not all plan types do, so we must be careful
+	 * not to generate an invalid plan.  If necessary, an invalid inner plan
+	 * can be handled by inserting a Materialize node.
+	 *
+	 * Since the inner side must be ordered, and only Sorts and IndexScans can
+	 * create order to begin with, you might think there's no problem --- but
+	 * you'd be wrong.  Nestloop and merge joins can *preserve* the order of
+	 * their inputs, so they can be selected as the input of a mergejoin,
+	 * and that won't work in the present executor.
+	 *
+	 * Doing this here is a bit of a kluge since the cost of the Materialize
+	 * wasn't taken into account in our earlier decisions.  But Materialize
+	 * is hard to estimate a cost for, and the above consideration shows that
+	 * this is a rare case anyway, so this seems an acceptable way to proceed.
+	 *
+	 * This check must agree with ExecMarkPos/ExecRestrPos in
+	 * executor/execAmi.c!
+	 */
+	switch (nodeTag(inner_node))
+	{
+		case T_SeqScan:
+		case T_IndexScan:
+		case T_Material:
+		case T_Sort:
+			/* OK, these inner plans support mark/restore */
+			break;
+
+		default:
+			/* Ooops, need to materialize the inner plan */
+			inner_node = (Plan *) make_material(inner_tlist,
+												_NONAME_RELATION_ID_,
+												inner_node,
+												0);
+			break;
+	}
+
 	join_node = make_mergejoin(tlist,
 							   qpqual,
 							   mergeclauses,

src/include/executor/nodeMaterial.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: nodeMaterial.h,v 1.12 2000/01/26 05:58:05 momjian Exp $
+ * $Id: nodeMaterial.h,v 1.12.2.1 2000/09/08 02:11:31 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -20,11 +20,8 @@ extern TupleTableSlot *ExecMaterial(Material *node);
 extern bool ExecInitMaterial(Material *node, EState *estate, Plan *parent);
 extern int	ExecCountSlotsMaterial(Material *node);
 extern void ExecEndMaterial(Material *node);
+extern void ExecMaterialMarkPos(Material *node);
+extern void ExecMaterialRestrPos(Material *node);
 extern void ExecMaterialReScan(Material *node, ExprContext *exprCtxt, Plan *parent);
 
-#ifdef NOT_USED
-extern List ExecMaterialMarkPos(Material *node);
-extern void ExecMaterialRestrPos(Material *node);
-
-#endif
 #endif	 /* NODEMATERIAL_H */