Fix set_append_rel_pathlist() to deal intelligently with cases where

substituting a child rel's output expressions into the appendrel's restriction
clauses yields a pseudoconstant restriction.  We might be able to skip scanning
that child rel entirely (if we get constant FALSE), or generate a one-time
filter.  8.3 more or less accidentally generated plans that weren't completely
stupid in these cases, but that was only because an extra recursive level of
subquery_planner() always occurred and allowed const-simplification to happen.
8.4's ability to pull up appendrel members with non-Var outputs exposes the
fact that we need to work harder here.  Per gripe from Sergey Burladyan.

1 files changed, 2 insertions, 52 deletions

diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index b5e10a91801..956b9559f82 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.171 2009/06/11 14:48:59 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.172 2009/07/06 18:26:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1636,57 +1636,7 @@ adjust_appendrel_attrs_mutator(Node *node, AppendRelInfo *context)
 	Assert(!IsA(node, SpecialJoinInfo));
 	Assert(!IsA(node, AppendRelInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
-
-	/*
-	 * We have to process RestrictInfo nodes specially.
-	 */
-	if (IsA(node, RestrictInfo))
-	{
-		RestrictInfo *oldinfo = (RestrictInfo *) node;
-		RestrictInfo *newinfo = makeNode(RestrictInfo);
-
-		/* Copy all flat-copiable fields */
-		memcpy(newinfo, oldinfo, sizeof(RestrictInfo));
-
-		/* Recursively fix the clause itself */
-		newinfo->clause = (Expr *)
-			adjust_appendrel_attrs_mutator((Node *) oldinfo->clause, context);
-
-		/* and the modified version, if an OR clause */
-		newinfo->orclause = (Expr *)
-			adjust_appendrel_attrs_mutator((Node *) oldinfo->orclause, context);
-
-		/* adjust relid sets too */
-		newinfo->clause_relids = adjust_relid_set(oldinfo->clause_relids,
-												  context->parent_relid,
-												  context->child_relid);
-		newinfo->required_relids = adjust_relid_set(oldinfo->required_relids,
-													context->parent_relid,
-													context->child_relid);
-		newinfo->left_relids = adjust_relid_set(oldinfo->left_relids,
-												context->parent_relid,
-												context->child_relid);
-		newinfo->right_relids = adjust_relid_set(oldinfo->right_relids,
-												 context->parent_relid,
-												 context->child_relid);
-
-		/*
-		 * Reset cached derivative fields, since these might need to have
-		 * different values when considering the child relation.
-		 */
-		newinfo->eval_cost.startup = -1;
-		newinfo->norm_selec = -1;
-		newinfo->outer_selec = -1;
-		newinfo->left_ec = NULL;
-		newinfo->right_ec = NULL;
-		newinfo->left_em = NULL;
-		newinfo->right_em = NULL;
-		newinfo->scansel_cache = NIL;
-		newinfo->left_bucketsize = -1;
-		newinfo->right_bucketsize = -1;
-
-		return (Node *) newinfo;
-	}
+	Assert(!IsA(node, RestrictInfo));
 
 	/*
 	 * NOTE: we do not need to recurse into sublinks, because they should