Restructure handling of inheritance queries so that they work with outer

joins, and clean things up a good deal at the same time.  Append plan node
no longer hacks on rangetable at runtime --- instead, all child tables are
given their own RT entries during planning.  Concept of multiple target
tables pushed up into execMain, replacing bug-prone implementation within
nodeAppend.  Planner now supports generating Append plans for inheritance
sets either at the top of the plan (the old way) or at the bottom.  Expanding
at the bottom is appropriate for tables used as sources, since they may
appear inside an outer join; but we must still expand at the top when the
target of an UPDATE or DELETE is an inheritance set, because we actually need
a different targetlist and junkfilter for each target table in that case.
Fortunately a target table can't be inside an outer join...  Bizarre mutual
recursion between union_planner and prepunion.c is gone --- in fact,
union_planner doesn't really have much to do with union queries anymore,
so I renamed it grouping_planner.

src/include/nodes/parsenodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: parsenodes.h,v 1.119 2000/11/05 22:50:21 vadim Exp $
+ * $Id: parsenodes.h,v 1.120 2000/11/12 00:37:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -70,6 +70,16 @@ typedef struct Query
 	Node	   *setOperations;	/* set-operation tree if this is top level
 								 * of a UNION/INTERSECT/EXCEPT query */
 
+	/*
+	 * If the resultRelation turns out to be the parent of an inheritance
+	 * tree, the planner will add all the child tables to the rtable and
+	 * store a list of the rtindexes of all the result relations here.
+	 * This is done at plan time, not parse time, since we don't want to
+	 * commit to the exact set of child tables at parse time.  This field
+	 * ought to go in some sort of TopPlan plan node, not in the Query.
+	 */
+	List	   *resultRelations; /* integer list of RT indexes, or NIL */
+
 	/* internal to planner */
 	List	   *base_rel_list;	/* list of base-relation RelOptInfos */
 	List	   *join_rel_list;	/* list of join-relation RelOptInfos */