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/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 */