Adjust the definition of RestrictInfo's left_relids and right_relids

fields: now they are valid whenever the clause is a binary opclause,
not only when it is a potential join clause (there is a new boolean
field canjoin to signal the latter condition).  This lets us avoid
recomputing the relid sets over and over while examining indexes.
Still more work to do to make this as useful as it could be, because
there are places that could use the info but don't have access to the
RestrictInfo node.

src/backend/optimizer/util/clauses.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.157 2003/12/28 21:57:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.158 2003/12/30 23:53:15 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -811,6 +811,20 @@ is_pseudo_constant_clause(Node *clause)
 	return false;
 }
 
+/*
+ * is_pseudo_constant_clause_relids
+ *	  Same as above, except caller already has available the var membership
+ *	  of the clause; this lets us avoid the contain_var_clause() scan.
+ */
+bool
+is_pseudo_constant_clause_relids(Node *clause, Relids relids)
+{
+	if (bms_is_empty(relids) &&
+		!contain_volatile_functions(clause))
+		return true;
+	return false;
+}
+
 /*
  * pull_constant_clauses
  *		Scan through a list of qualifications and separate "constant" quals