Add some defenses to guard against case where a rule refers to a table

or view that's been dropped and then recreated with the same name (but,
perhaps, different columns).  Eventually we'd like to support this but
for now all we can do is fail cleanly, rather than possibly coredumping
if we proceed using the obsolete rule.

src/backend/rewrite/rewriteHandler.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.91 2001/03/22 06:16:16 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.92 2001/04/17 00:32:58 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -486,16 +486,25 @@ fireRIRrules(Query *parsetree)
 
 		rel = heap_openr(rte->relname, lockmode);
 
+		/*
+		 * Check to see if relation's OID matches the RTE.  If not, the RTE
+		 * actually refers to an older relation that had the same name.
+		 * Eventually we might want to reparse the referencing rule, but
+		 * for now all we can do is punt.
+		 */
+		if (RelationGetRelid(rel) != rte->relid)
+			elog(ERROR, "Relation \"%s\" with OID %u no longer exists",
+				 rte->relname, rte->relid);
+
+		/*
+		 * Collect the RIR rules that we must apply
+		 */
 		rules = rel->rd_rules;
 		if (rules == NULL)
 		{
 			heap_close(rel, NoLock);
 			continue;
 		}
-
-		/*
-		 * Collect the RIR rules that we must apply
-		 */
 		locks = NIL;
 		for (i = 0; i < rules->numLocks; i++)
 		{
@@ -776,6 +785,19 @@ RewriteQuery(Query *parsetree, bool *instead_flag, List **qual_products)
 	 */
 	rt_entry_relation = heap_openr(rt_entry->relname, RowExclusiveLock);
 
+	/*
+	 * Check to see if relation's OID matches the RTE.  If not, the RTE
+	 * actually refers to an older relation that had the same name.
+	 * Eventually we might want to reparse the referencing rule, but
+	 * for now all we can do is punt.
+	 */
+	if (RelationGetRelid(rt_entry_relation) != rt_entry->relid)
+		elog(ERROR, "Relation \"%s\" with OID %u no longer exists",
+			 rt_entry->relname, rt_entry->relid);
+
+	/*
+	 * Collect and apply the appropriate rules.
+	 */
 	rt_entry_locks = rt_entry_relation->rd_rules;
 
 	if (rt_entry_locks != NULL)