Fix "constraint_exclusion = partition" logic so that it will also attempt

constraint exclusion on an inheritance set that is the target of an UPDATE
or DELETE query.  Per gripe from Marc Cousin.  Back-patch to 8.4 where
the feature was introduced.

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.384 2010/03/28 22:59:32 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.385 2010/03/30 21:58:10 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -1559,6 +1559,7 @@ _outPlannerInfo(StringInfo str, PlannerInfo *node)
 	WRITE_NODE_FIELD(sort_pathkeys);
 	WRITE_FLOAT_FIELD(total_table_pages, "%.0f");
 	WRITE_FLOAT_FIELD(tuple_fraction, "%.4f");
+	WRITE_BOOL_FIELD(hasInheritedTarget);
 	WRITE_BOOL_FIELD(hasJoinRTEs);
 	WRITE_BOOL_FIELD(hasHavingQual);
 	WRITE_BOOL_FIELD(hasPseudoConstantQuals);

src/backend/optimizer/plan/planner.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.266 2010/02/26 02:00:45 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.267 2010/03/30 21:58:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -307,6 +307,7 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
 	root->eq_classes = NIL;
 	root->append_rel_list = NIL;
 	root->rowMarks = NIL;
+	root->hasInheritedTarget = false;
 
 	root->hasRecursion = hasRecursion;
 	if (hasRecursion)
@@ -749,6 +750,7 @@ inheritance_planner(PlannerInfo *root)
 			adjust_appendrel_attrs((Node *) parse,
 								   appinfo);
 		subroot.init_plans = NIL;
+		subroot.hasInheritedTarget = true;
 		/* We needn't modify the child's append_rel_list */
 		/* There shouldn't be any OJ info to translate, as yet */
 		Assert(subroot.join_info_list == NIL);

src/backend/optimizer/util/plancat.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.162 2010/01/05 21:53:58 rhaas Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.163 2010/03/30 21:58:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -580,7 +580,10 @@ relation_excluded_by_constraints(PlannerInfo *root,
 	/* Skip the test if constraint exclusion is disabled for the rel */
 	if (constraint_exclusion == CONSTRAINT_EXCLUSION_OFF ||
 		(constraint_exclusion == CONSTRAINT_EXCLUSION_PARTITION &&
-		 rel->reloptkind != RELOPT_OTHER_MEMBER_REL))
+		 !(rel->reloptkind == RELOPT_OTHER_MEMBER_REL ||
+		   (root->hasInheritedTarget &&
+			rel->reloptkind == RELOPT_BASEREL &&
+			rel->relid == root->parse->resultRelation))))
 		return false;
 
 	/*

src/include/nodes/relation.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.185 2010/03/28 22:59:33 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.186 2010/03/30 21:58:11 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -197,6 +197,8 @@ typedef struct PlannerInfo
 
 	double		tuple_fraction; /* tuple_fraction passed to query_planner */
 
+	bool		hasInheritedTarget;	/* true if parse->resultRelation is an
+									 * inheritance child rel */
 	bool		hasJoinRTEs;	/* true if any RTEs are RTE_JOIN kind */
 	bool		hasHavingQual;	/* true if havingQual was non-null */
 	bool		hasPseudoConstantQuals; /* true if any RestrictInfo has