Create a standardized expression_tree_mutator support routine

to go along with expression_tree_walker.  (_walker is not suitable for
routines that need to alter the tree structure significantly.)  Other minor
cleanups in clauses.c.

src/backend/optimizer/prep/preptlist.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.27 1999/07/17 20:17:16 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.28 1999/08/09 00:51:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -45,10 +45,9 @@ preprocess_targetlist(List *tlist,
 					  Index result_relation,
 					  List *range_table)
 {
-	List	   *expanded_tlist = NIL;
 	Oid			relid = InvalidOid;
-	List	   *t_list = NIL;
-	List	   *temp = NIL;
+	List	   *expanded_tlist;
+	List	   *t_list;
 
 	if (result_relation >= 1 && command_type != CMD_SELECT)
 		relid = getrelid(result_relation, range_table);
@@ -61,14 +60,7 @@ preprocess_targetlist(List *tlist,
 	expanded_tlist = expand_targetlist(tlist, relid, command_type, result_relation);
 
 	/* XXX should the fix-opids be this early?? */
-	/* was mapCAR  */
-	foreach(temp, expanded_tlist)
-	{
-		TargetEntry *tle = lfirst(temp);
-
-		if (tle->expr)
-			fix_opid(tle->expr);
-	}
+	fix_opids(expanded_tlist);
 	t_list = copyObject(expanded_tlist);
 
 	/* ------------------

src/include/optimizer/clauses.h

@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: clauses.h,v 1.24 1999/07/27 03:51:00 tgl Exp $
+ * $Id: clauses.h,v 1.25 1999/08/09 00:51:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -44,7 +44,6 @@ extern void clause_get_relids_vars(Node *clause, Relids *relids, List **vars);
 extern int	NumRelids(Node *clause);
 extern bool is_joinable(Node *clause);
 extern bool qual_clause_p(Node *clause);
-extern void fix_opid(Node *clause);
 extern List *fix_opids(List *clauses);
 extern void get_relattval(Node *clause, int targetrelid,
 						  int *relid, AttrNumber *attno,
@@ -55,6 +54,8 @@ extern void CommuteClause(Node *clause);
 
 extern bool expression_tree_walker(Node *node, bool (*walker) (),
 								   void *context);
+extern Node *expression_tree_mutator(Node *node, Node * (*mutator) (),
+									 void *context);
 
 #define is_subplan(clause)	((Node*) (clause) != NULL && \
 						nodeTag((Node*) (clause)) == T_Expr && \