Check readiness in add_to_pathman_config

Author: ildus

Diff for: expected/pathman_calamity.out

@@ -1005,7 +1005,7 @@ SHOW pg_pathman.enable;
 (1 row)
 
 SELECT add_to_pathman_config('calamity.survivor', 'val', '10');	/* not ok */
-ERROR:  pg_pathman is not initialized yet
+ERROR:  pg_pathman is disabled
 SELECT * FROM pathman_partition_list;							/* not ok */
 ERROR:  pg_pathman is not initialized yet
 SELECT get_part_range('calamity.survivor', 0, NULL::INT);		/* not ok */

Diff for: src/pl_funcs.c

@@ -740,6 +740,9 @@ add_to_pathman_config(PG_FUNCTION_ARGS)
 
 	PathmanInitState	init_state;
 
+	if (!IsPathmanReady())
+		elog(ERROR, "pg_pathman is disabled");
+
 	if (!PG_ARGISNULL(0))
 	{
 		relid = PG_GETARG_OID(0);