Make sure we give an appropriate user-facing error when attempting

to drop a table that is referenced by an open cursor.  Fix unstable
ecpg regression test result that was produced by this oversight.

src/backend/catalog/heap.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.346 2008/11/27 15:59:28 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.347 2008/11/29 00:13:21 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1412,6 +1412,17 @@ heap_drop_with_catalog(Oid relid)
 	 */
 	rel = relation_open(relid, AccessExclusiveLock);
 
+	/*
+	 * There can no longer be anyone *else* touching the relation, but we
+	 * might still have open queries or cursors in our own session.
+	 */
+	if (rel->rd_refcnt != 1)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_IN_USE),
+				 errmsg("cannot drop \"%s\" because "
+						"it is being used by active queries in this session",
+						RelationGetRelationName(rel))));
+
 	/*
 	 * Schedule unlinking of the relation's physical files at commit.
 	 */

src/interfaces/ecpg/test/expected/sql-fetch.stderr

@@ -138,10 +138,10 @@
 [NO_PID]: sqlca: code: 0, state: 00000
 [NO_PID]: ecpg_execute on line 53: using PQexec
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_check_PQresult on line 53: ERROR:  relation 16491 is still open
+[NO_PID]: ecpg_check_PQresult on line 53: ERROR:  cannot drop "my_table" because it is being used by active queries in this session
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: raising sqlstate XX000 (sqlcode -400) on line 53: relation 16491 is still open on line 53
-[NO_PID]: sqlca: code: -400, state: XX000
-sql error: relation 16491 is still open on line 53
+[NO_PID]: raising sqlstate 55006 (sqlcode -400) on line 53: cannot drop "my_table" because it is being used by active queries in this session on line 53
+[NO_PID]: sqlca: code: -400, state: 55006
+sql error: cannot drop "my_table" because it is being used by active queries in this session on line 53
 [NO_PID]: ecpg_finish: connection regress1 closed
 [NO_PID]: sqlca: code: 0, state: 00000