Fix an oversight I made in a cleanup patch over a year ago:

eval_const_expressions needs to be passed the PlannerInfo ("root") structure,
because in some cases we want it to substitute values for Param nodes.
(So "constant" is not so constant as all that ...)  This mistake partially
disabled optimization of unnamed extended-Query statements in 8.3: in
particular the LIKE-to-indexscan optimization would never be applied if the
LIKE pattern was passed as a parameter, and constraint exclusion depending
on a parameter value didn't work either.

src/backend/optimizer/path/allpaths.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.169 2008/03/24 21:53:03 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.170 2008/04/01 00:48:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -205,7 +205,7 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 	 * set_append_rel_pathlist().
 	 */
 	if (rel->reloptkind == RELOPT_BASEREL &&
-		relation_excluded_by_constraints(rel, rte))
+		relation_excluded_by_constraints(root, rel, rte))
 	{
 		set_dummy_rel_pathlist(rel);
 		return;
@@ -321,7 +321,7 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 			adjust_appendrel_attrs((Node *) rel->baserestrictinfo,
 								   appinfo);
 
-		if (relation_excluded_by_constraints(childrel, childRTE))
+		if (relation_excluded_by_constraints(root, childrel, childRTE))
 		{
 			/*
 			 * This child need not be scanned, so we can omit it from the

src/backend/optimizer/plan/initsplan.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.138 2008/01/09 20:42:28 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.139 2008/04/01 00:48:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1219,7 +1219,7 @@ process_implied_equality(PlannerInfo *root,
 	/* If both constant, try to reduce to a boolean constant. */
 	if (both_const)
 	{
-		clause = (Expr *) eval_const_expressions((Node *) clause);
+		clause = (Expr *) eval_const_expressions(root, (Node *) clause);
 
 		/* If we produced const TRUE, just drop the clause */
 		if (clause && IsA(clause, Const))

src/backend/optimizer/plan/planner.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.230 2008/03/29 00:15:28 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.231 2008/04/01 00:48:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -503,7 +503,7 @@ preprocess_expression(PlannerInfo *root, Node *expr, int kind)
 		(root->parse->jointree->fromlist != NIL ||
 		 kind == EXPRKIND_QUAL ||
 		 root->query_level > 1))
-		expr = eval_const_expressions(expr);
+		expr = eval_const_expressions(root, expr);
 
 	/*
 	 * If it's a qual or havingQual, canonicalize it.

src/backend/optimizer/util/clauses.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.256 2008/03/25 22:42:43 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.257 2008/04/01 00:48:33 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -1687,16 +1687,22 @@ rowtype_field_matches(Oid rowtypeid, int fieldnum,
  * We assume that the tree has already been type-checked and contains
  * only operators and functions that are reasonable to try to execute.
  *
+ * NOTE: "root" can be passed as NULL if the caller never wants to do any
+ * Param substitutions.
+ *
  * NOTE: the planner assumes that this will always flatten nested AND and
  * OR clauses into N-argument form.  See comments in prepqual.c.
  *--------------------
  */
 Node *
-eval_const_expressions(Node *node)
+eval_const_expressions(PlannerInfo *root, Node *node)
 {
 	eval_const_expressions_context context;
 
-	context.boundParams = NULL; /* don't use any bound params */
+	if (root)
+		context.boundParams = root->glob->boundParams;	/* bound Params */
+	else
+		context.boundParams = NULL;
 	context.active_fns = NIL;	/* nothing being recursively simplified */
 	context.case_val = NULL;	/* no CASE being examined */
 	context.estimate = false;	/* safe transformations only */

src/backend/optimizer/util/plancat.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.144 2008/03/26 21:10:38 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.145 2008/04/01 00:48:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -47,7 +47,8 @@ bool		constraint_exclusion = false;
 get_relation_info_hook_type get_relation_info_hook = NULL;
 
 
-static List *get_relation_constraints(Oid relationObjectId, RelOptInfo *rel,
+static List *get_relation_constraints(PlannerInfo *root,
+						 Oid relationObjectId, RelOptInfo *rel,
 						 bool include_notnull);
 
 
@@ -462,7 +463,8 @@ estimate_rel_size(Relation rel, int32 *attr_widths,
  * point in caching the data in RelOptInfo.
  */
 static List *
-get_relation_constraints(Oid relationObjectId, RelOptInfo *rel,
+get_relation_constraints(PlannerInfo *root,
+						 Oid relationObjectId, RelOptInfo *rel,
 						 bool include_notnull)
 {
 	List	   *result = NIL;
@@ -497,7 +499,7 @@ get_relation_constraints(Oid relationObjectId, RelOptInfo *rel,
 			 * stuff involving subqueries, however, since we don't allow any
 			 * in check constraints.)
 			 */
-			cexpr = eval_const_expressions(cexpr);
+			cexpr = eval_const_expressions(root, cexpr);
 
 			cexpr = (Node *) canonicalize_qual((Expr *) cexpr);
 
@@ -561,7 +563,8 @@ get_relation_constraints(Oid relationObjectId, RelOptInfo *rel,
  * it can be called before filling in other fields of the RelOptInfo.
  */
 bool
-relation_excluded_by_constraints(RelOptInfo *rel, RangeTblEntry *rte)
+relation_excluded_by_constraints(PlannerInfo *root,
+								 RelOptInfo *rel, RangeTblEntry *rte)
 {
 	List	   *safe_restrictions;
 	List	   *constraint_pred;
@@ -600,7 +603,7 @@ relation_excluded_by_constraints(RelOptInfo *rel, RangeTblEntry *rte)
 	 * OK to fetch the constraint expressions.  Include "col IS NOT NULL"
 	 * expressions for attnotnull columns, in case we can refute those.
 	 */
-	constraint_pred = get_relation_constraints(rte->relid, rel, true);
+	constraint_pred = get_relation_constraints(root, rte->relid, rel, true);
 
 	/*
 	 * We do not currently enforce that CHECK constraints contain only

src/backend/utils/cache/relcache.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.269 2008/03/26 21:10:39 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.270 2008/04/01 00:48:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3068,7 +3068,7 @@ RelationGetIndexExpressions(Relation relation)
 	 * them to similarly-processed qual clauses, and may fail to detect valid
 	 * matches without this.  We don't bother with canonicalize_qual, however.
 	 */
-	result = (List *) eval_const_expressions((Node *) result);
+	result = (List *) eval_const_expressions(NULL, (Node *) result);
 
 	/*
 	 * Also mark any coercion format fields as "don't care", so that the
@@ -3138,7 +3138,7 @@ RelationGetIndexPredicate(Relation relation)
 	 * stuff involving subqueries, however, since we don't allow any in index
 	 * predicates.)
 	 */
-	result = (List *) eval_const_expressions((Node *) result);
+	result = (List *) eval_const_expressions(NULL, (Node *) result);
 
 	result = (List *) canonicalize_qual((Expr *) result);
 

src/include/optimizer/clauses.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/optimizer/clauses.h,v 1.89 2008/03/18 22:04:14 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/clauses.h,v 1.90 2008/04/01 00:48:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -75,7 +75,7 @@ extern Node *strip_implicit_coercions(Node *node);
 
 extern void set_coercionform_dontcare(Node *node);
 
-extern Node *eval_const_expressions(Node *node);
+extern Node *eval_const_expressions(PlannerInfo *root, Node *node);
 
 extern Node *estimate_expression_value(PlannerInfo *root, Node *node);
 

src/include/optimizer/plancat.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/optimizer/plancat.h,v 1.48 2008/03/15 20:46:31 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/plancat.h,v 1.49 2008/04/01 00:48:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -31,8 +31,8 @@ extern void get_relation_info(PlannerInfo *root, Oid relationObjectId,
 extern void estimate_rel_size(Relation rel, int32 *attr_widths,
 							  BlockNumber *pages, double *tuples);
 
-extern bool relation_excluded_by_constraints(RelOptInfo *rel,
-								 RangeTblEntry *rte);
+extern bool relation_excluded_by_constraints(PlannerInfo *root,
+								 RelOptInfo *rel, RangeTblEntry *rte);
 
 extern List *build_physical_tlist(PlannerInfo *root, RelOptInfo *rel);