Reconsider mechanism for marking sub-selects that are at top level of

a qualification clause (and hence can get away with being sloppy about
distinguishing FALSE from UNKNOWN).  We need to know this in subselect.c;
marking the subplans in setrefs.c is too late.

src/backend/optimizer/plan/planner.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.137 2003/01/13 00:29:25 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.138 2003/01/13 18:10:53 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -777,7 +777,7 @@ preprocess_expression(Query *parse, Node *expr, int kind)
 
 	/* Expand SubLinks to SubPlans */
 	if (parse->hasSubLinks)
-		expr = SS_process_sublinks(expr);
+		expr = SS_process_sublinks(expr, (kind != EXPRKIND_TARGET));
 
 	/* Replace uplevel vars with Param nodes */
 	if (PlannerQueryLevel > 1)

src/backend/optimizer/plan/setrefs.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/setrefs.c,v 1.87 2003/01/10 21:08:11 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/setrefs.c,v 1.88 2003/01/13 18:10:53 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -42,7 +42,6 @@ typedef struct
 
 static void fix_expr_references(Plan *plan, Node *node);
 static bool fix_expr_references_walker(Node *node, void *context);
-static void mark_qual_expressions(List *quals);
 static void set_join_references(Join *join, List *rtable);
 static void set_uppernode_references(Plan *plan, Index subvarno);
 static Node *join_references_mutator(Node *node,
@@ -89,12 +88,10 @@ set_plan_references(Plan *plan, List *rtable)
 		case T_SeqScan:
 			fix_expr_references(plan, (Node *) plan->targetlist);
 			fix_expr_references(plan, (Node *) plan->qual);
-			mark_qual_expressions(plan->qual);
 			break;
 		case T_IndexScan:
 			fix_expr_references(plan, (Node *) plan->targetlist);
 			fix_expr_references(plan, (Node *) plan->qual);
-			mark_qual_expressions(plan->qual);
 			fix_expr_references(plan,
 								(Node *) ((IndexScan *) plan)->indxqual);
 			fix_expr_references(plan,
@@ -103,7 +100,6 @@ set_plan_references(Plan *plan, List *rtable)
 		case T_TidScan:
 			fix_expr_references(plan, (Node *) plan->targetlist);
 			fix_expr_references(plan, (Node *) plan->qual);
-			mark_qual_expressions(plan->qual);
 			fix_expr_references(plan,
 								(Node *) ((TidScan *) plan)->tideval);
 			break;
@@ -118,7 +114,6 @@ set_plan_references(Plan *plan, List *rtable)
 				 */
 				fix_expr_references(plan, (Node *) plan->targetlist);
 				fix_expr_references(plan, (Node *) plan->qual);
-				mark_qual_expressions(plan->qual);
 
 				/* Recurse into subplan too */
 				rte = rt_fetch(((SubqueryScan *) plan)->scan.scanrelid,
@@ -134,7 +129,6 @@ set_plan_references(Plan *plan, List *rtable)
 
 				fix_expr_references(plan, (Node *) plan->targetlist);
 				fix_expr_references(plan, (Node *) plan->qual);
-				mark_qual_expressions(plan->qual);
 				rte = rt_fetch(((FunctionScan *) plan)->scan.scanrelid,
 							   rtable);
 				Assert(rte->rtekind == RTE_FUNCTION);
@@ -145,17 +139,13 @@ set_plan_references(Plan *plan, List *rtable)
 			set_join_references((Join *) plan, rtable);
 			fix_expr_references(plan, (Node *) plan->targetlist);
 			fix_expr_references(plan, (Node *) plan->qual);
-			mark_qual_expressions(plan->qual);
 			fix_expr_references(plan, (Node *) ((Join *) plan)->joinqual);
-			mark_qual_expressions(((Join *) plan)->joinqual);
 			break;
 		case T_MergeJoin:
 			set_join_references((Join *) plan, rtable);
 			fix_expr_references(plan, (Node *) plan->targetlist);
 			fix_expr_references(plan, (Node *) plan->qual);
-			mark_qual_expressions(plan->qual);
 			fix_expr_references(plan, (Node *) ((Join *) plan)->joinqual);
-			mark_qual_expressions(((Join *) plan)->joinqual);
 			fix_expr_references(plan,
 							(Node *) ((MergeJoin *) plan)->mergeclauses);
 			break;
@@ -163,9 +153,7 @@ set_plan_references(Plan *plan, List *rtable)
 			set_join_references((Join *) plan, rtable);
 			fix_expr_references(plan, (Node *) plan->targetlist);
 			fix_expr_references(plan, (Node *) plan->qual);
-			mark_qual_expressions(plan->qual);
 			fix_expr_references(plan, (Node *) ((Join *) plan)->joinqual);
-			mark_qual_expressions(((Join *) plan)->joinqual);
 			fix_expr_references(plan,
 							  (Node *) ((HashJoin *) plan)->hashclauses);
 			break;
@@ -192,7 +180,6 @@ set_plan_references(Plan *plan, List *rtable)
 			set_uppernode_references(plan, (Index) 0);
 			fix_expr_references(plan, (Node *) plan->targetlist);
 			fix_expr_references(plan, (Node *) plan->qual);
-			mark_qual_expressions(plan->qual);
 			break;
 		case T_Result:
 
@@ -206,9 +193,7 @@ set_plan_references(Plan *plan, List *rtable)
 				set_uppernode_references(plan, (Index) OUTER);
 			fix_expr_references(plan, (Node *) plan->targetlist);
 			fix_expr_references(plan, (Node *) plan->qual);
-			mark_qual_expressions(plan->qual);
 			fix_expr_references(plan, ((Result *) plan)->resconstantqual);
-			mark_qual_expressions((List *) ((Result *) plan)->resconstantqual);
 			break;
 		case T_Append:
 
@@ -283,28 +268,6 @@ fix_expr_references_walker(Node *node, void *context)
 	return expression_tree_walker(node, fix_expr_references_walker, context);
 }
 
-/*
- * mark_qual_expressions
- *	  Do final cleanup on qualifier expressions (not targetlists!)
- *
- * SubPlans appearing at the top level of a qual expression are marked
- * to indicate that they need not distinguish UNKNOWN (null) from FALSE
- * results; this can save processing time in some cases.
- */
-static void
-mark_qual_expressions(List *quals)
-{
-	List   *qual;
-
-	foreach(qual, quals)
-	{
-		Node   *node = lfirst(qual);
-
-		if (IsA(node, SubPlan))
-			((SubPlan *) node)->unknownEqFalse = true;
-	}
-}
-
 /*
  * set_join_references
  *	  Modifies the target list of a join node to reference its subplans,

src/backend/optimizer/plan/subselect.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.65 2003/01/13 00:29:26 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.66 2003/01/13 18:10:53 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -65,7 +65,7 @@ static List *convert_sublink_opers(List *lefthand, List *operOids,
 								   List *targetlist, List **paramIds);
 static bool subplan_is_hashable(SubLink *slink, SubPlan *node);
 static Node *replace_correlation_vars_mutator(Node *node, void *context);
-static Node *process_sublinks_mutator(Node *node, void *context);
+static Node *process_sublinks_mutator(Node *node, bool *isTopQual);
 static bool finalize_primnode(Node *node, finalize_primnode_results *results);
 
 
@@ -159,7 +159,8 @@ generate_new_param(Oid paramtype, int32 paramtypmod)
  * Convert a bare SubLink (as created by the parser) into a SubPlan.
  *
  * We are given the raw SubLink and the already-processed lefthand argument
- * list (use this instead of the SubLink's own field).
+ * list (use this instead of the SubLink's own field).  We are also told if
+ * this expression appears at top level of a WHERE/HAVING qual.
  *
  * The result is whatever we need to substitute in place of the SubLink
  * node in the executable expression.  This will be either the SubPlan
@@ -168,7 +169,7 @@ generate_new_param(Oid paramtype, int32 paramtypmod)
  * containing InitPlan Param nodes.
  */
 static Node *
-make_subplan(SubLink *slink, List *lefthand)
+make_subplan(SubLink *slink, List *lefthand, bool isTopQual)
 {
 	SubPlan	   *node = makeNode(SubPlan);
 	Query	   *subquery = (Query *) (slink->subselect);
@@ -232,7 +233,8 @@ make_subplan(SubLink *slink, List *lefthand)
 	node->exprs = NIL;
 	node->paramIds = NIL;
 	node->useHashTable = false;
-	node->unknownEqFalse = false;
+	/* At top level of a qual, can treat UNKNOWN the same as FALSE */
+	node->unknownEqFalse = isTopQual;
 	node->setParam = NIL;
 	node->parParam = NIL;
 	node->args = NIL;
@@ -589,17 +591,23 @@ replace_correlation_vars_mutator(Node *node, void *context)
 
 /*
  * Expand SubLinks to SubPlans in the given expression.
+ *
+ * The isQual argument tells whether or not this expression is a WHERE/HAVING
+ * qualifier expression.  If it is, any sublinks appearing at top level need
+ * not distinguish FALSE from UNKNOWN return values.
  */
 Node *
-SS_process_sublinks(Node *expr)
+SS_process_sublinks(Node *expr, bool isQual)
 {
-	/* No setup needed for tree walk, so away we go */
-	return process_sublinks_mutator(expr, NULL);
+	/* The only context needed is the initial are-we-in-a-qual flag */
+	return process_sublinks_mutator(expr, &isQual);
 }
 
 static Node *
-process_sublinks_mutator(Node *node, void *context)
+process_sublinks_mutator(Node *node, bool *isTopQual)
 {
+	bool	locTopQual;
+
 	if (node == NULL)
 		return NULL;
 	if (IsA(node, SubLink))
@@ -610,12 +618,13 @@ process_sublinks_mutator(Node *node, void *context)
 		/*
 		 * First, recursively process the lefthand-side expressions, if any.
 		 */
+		locTopQual = false;
 		lefthand = (List *)
-			process_sublinks_mutator((Node *) sublink->lefthand, context);
+			process_sublinks_mutator((Node *) sublink->lefthand, &locTopQual);
 		/*
 		 * Now build the SubPlan node and make the expr to return.
 		 */
-		return make_subplan(sublink, lefthand);
+		return make_subplan(sublink, lefthand, *isTopQual);
 	}
 
 	/*
@@ -626,9 +635,18 @@ process_sublinks_mutator(Node *node, void *context)
 	 */
 	Assert(!is_subplan(node));
 
+	/*
+	 * If we recurse down through anything other than a List node, we are
+	 * definitely not at top qual level anymore.
+	 */
+	if (IsA(node, List))
+		locTopQual = *isTopQual;
+	else
+		locTopQual = false;
+
 	return expression_tree_mutator(node,
 								   process_sublinks_mutator,
-								   context);
+								   (void *) &locTopQual);
 }
 
 /*

src/include/optimizer/subselect.h

@@ -16,6 +16,6 @@ extern int	PlannerPlanId;		/* to assign unique ID to subquery plans */
 
 extern List *SS_finalize_plan(Plan *plan, List *rtable);
 extern Node *SS_replace_correlation_vars(Node *expr);
-extern Node *SS_process_sublinks(Node *expr);
+extern Node *SS_process_sublinks(Node *expr, bool isQual);
 
 #endif   /* SUBSELECT_H */