Phase 2 of read-only-plans project: restructure expression-tree nodes

so that all executable expression nodes inherit from a common supertype
Expr.  This is somewhat of an exercise in code purity rather than any
real functional advance, but getting rid of the extra Oper or Func node
formerly used in each operator or function call should provide at least
a little space and speed improvement.
initdb forced by changes in stored-rules representation.

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 1.59 2002/12/05 15:50:35 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.60 2002/12/12 15:49:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -144,12 +144,12 @@ generate_new_param(Oid paramtype, int32 paramtypmod)
 }
 
 /*
- * Convert a bare SubLink (as created by the parser) into a SubPlan.
+ * Convert a bare SubLink (as created by the parser) into a SubPlanExpr.
  */
 static Node *
 make_subplan(SubLink *slink)
 {
-	SubPlan    *node = makeNode(SubPlan);
+	SubPlanExpr *node = makeNode(SubPlanExpr);
 	Query	   *subquery = (Query *) (slink->subselect);
 	Oid			result_type = exprType((Node *) slink);
 	double		tuple_fraction;
@@ -210,11 +210,13 @@ make_subplan(SubLink *slink)
 	node->plan = plan = subquery_planner(subquery, tuple_fraction);
 
 	node->plan_id = PlannerPlanId++;	/* Assign unique ID to this
-										 * SubPlan */
+										 * SubPlanExpr */
 
 	node->rtable = subquery->rtable;
 	node->sublink = slink;
 
+	node->typeOid = result_type;
+
 	slink->subselect = NULL;	/* cool ?! see error check above! */
 
 	/*
@@ -270,7 +272,6 @@ make_subplan(SubLink *slink)
 	}
 	else
 	{
-		Expr	   *expr = makeNode(Expr);
 		List	   *args = NIL;
 
 		/*
@@ -350,14 +351,7 @@ make_subplan(SubLink *slink)
 		convert_sublink_opers(slink, plan->targetlist, NULL);
 
 		/*
-		 * Make expression of SUBPLAN type
-		 */
-		expr->typeOid = result_type;
-		expr->opType = SUBPLAN_EXPR;
-		expr->oper = (Node *) node;
-
-		/*
-		 * Make expr->args from parParam.
+		 * Make node->args from parParam.
 		 */
 		foreach(lst, node->parParam)
 		{
@@ -373,9 +367,9 @@ make_subplan(SubLink *slink)
 			var->varlevelsup = 0;
 			args = lappend(args, var);
 		}
-		expr->args = args;
+		node->args = args;
 
-		result = (Node *) expr;
+		result = (Node *) node;
 	}
 
 	return result;
@@ -385,7 +379,7 @@ make_subplan(SubLink *slink)
  * convert_sublink_opers: convert a SubLink's oper list from the
  * parser/rewriter format into the executor's format.
  *
- * The oper list is initially just a list of Oper nodes.  We replace it
+ * The oper list is initially just a list of OpExpr nodes.  We replace it
  * with a list of actually executable expressions, in which the specified
  * operators are applied to corresponding elements of the lefthand list
  * and Params representing the results of the subplan.  lefthand is then
@@ -404,7 +398,7 @@ convert_sublink_opers(SubLink *slink, List *targetlist,
 
 	foreach(lst, slink->oper)
 	{
-		Oper	   *oper = (Oper *) lfirst(lst);
+		OpExpr	   *oper = (OpExpr *) lfirst(lst);
 		Node	   *lefthand = lfirst(leftlist);
 		TargetEntry *te = lfirst(targetlist);
 		Param	   *prm;
@@ -422,7 +416,7 @@ convert_sublink_opers(SubLink *slink, List *targetlist,
 			*setParams = lappendi(*setParams, prm->paramid);
 
 		/* Look up the operator to check its declared input types */
-		Assert(IsA(oper, Oper));
+		Assert(IsA(oper, OpExpr));
 		tup = SearchSysCache(OPEROID,
 							 ObjectIdGetDatum(oper->opno),
 							 0, 0, 0);
@@ -439,9 +433,11 @@ convert_sublink_opers(SubLink *slink, List *targetlist,
 		left = make_operand(lefthand, exprType(lefthand), opform->oprleft);
 		right = make_operand((Node *) prm, prm->paramtype, opform->oprright);
 		newoper = lappend(newoper,
-						  make_opclause(oper,
-										(Var *) left,
-										(Var *) right));
+						  make_opclause(oper->opno,
+										oper->opresulttype,
+										oper->opretset,
+										(Expr *) left,
+										(Expr *) right));
 
 		ReleaseSysCache(tup);
 
@@ -482,7 +478,7 @@ finalize_primnode(Node *node, finalize_primnode_results *results)
 	}
 	if (is_subplan(node))
 	{
-		SubPlan    *subplan = (SubPlan *) ((Expr *) node)->oper;
+		SubPlanExpr *subplan = (SubPlanExpr *) node;
 		List	   *lst;
 
 		/* Check extParam list for params to add to paramids */
@@ -559,12 +555,12 @@ process_sublinks_mutator(Node *node, void *context)
 		 */
 		sublink->lefthand = (List *)
 			process_sublinks_mutator((Node *) sublink->lefthand, context);
-		/* Now build the SubPlan node and make the expr to return */
+		/* Now build the SubPlanExpr node and make the expr to return */
 		return make_subplan(sublink);
 	}
 
 	/*
-	 * Note that we will never see a SubPlan expression in the input
+	 * Note that we will never see a SubPlanExpr expression in the input
 	 * (since this is the very routine that creates 'em to begin with). So
 	 * the code in expression_tree_mutator() that might do inappropriate
 	 * things with SubPlans or SubLinks will not be exercised.