Do not use cached catalog in is_user

contrib/babelfishpg_tsql/src/catalog.c

@@ -851,35 +851,59 @@ get_authid_login_ext_idx_oid(void)
 bool
 is_user(Oid role_oid)
 {
+	Relation	relation;
 	bool		is_user = true;
+	ScanKeyData scanKey;
+	SysScanDesc scan;
 	HeapTuple	tuple;
 	HeapTuple	authtuple;
 	NameData	rolname;
+	char	   *type_str = "";
 
 	authtuple = SearchSysCache1(AUTHOID, ObjectIdGetDatum(role_oid));
 	if (!HeapTupleIsValid(authtuple))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_OBJECT),
 				 errmsg("role with OID %u does not exist", role_oid)));
 	rolname = ((Form_pg_authid) GETSTRUCT(authtuple))->rolname;
-	tuple = SearchSysCache1(AUTHIDUSEREXTROLENAME, NameGetDatum(&rolname));
+
+	relation = table_open(get_authid_user_ext_oid(), AccessShareLock);
+
+	ScanKeyInit(&scanKey,
+				Anum_bbf_authid_user_ext_rolname,
+				BTEqualStrategyNumber, F_NAMEEQ,
+				NameGetDatum(&rolname));
+
+	scan = systable_beginscan(relation,
+							  get_authid_user_ext_idx_oid(),
+							  true, NULL, 1, &scanKey);
+
+	tuple = systable_getnext(scan);
 
 	if (!HeapTupleIsValid(tuple))
 		is_user = false;
 	else
 	{
-		BpChar type = ((Form_authid_user_ext) GETSTRUCT(tuple))->type;
-		char *type_str = bpchar_to_cstring(&type);
+		Datum		datum;
+		bool		isnull;
+		TupleDesc	dsc;
 
-		/*
-		 * Only sysadmin can not be dropped. For the rest of the cases i.e., type
-		 * is "S" or "U" etc, we should drop the user
-		 */
-		if (strcmp(type_str, "R") == 0)
-			is_user = false;
-		ReleaseSysCache(tuple);
+		dsc = RelationGetDescr(relation);
+		datum = heap_getattr(tuple, USER_EXT_TYPE + 1, dsc, &isnull);
+		if (!isnull)
+			type_str = pstrdup(TextDatumGetCString(datum));
 	}
 
+	/*
+	 * Only sysadmin can not be dropped. For the rest of the cases i.e., type
+	 * is "S" or "U" etc, we should drop the user
+	 */
+	if (strcmp(type_str, "R") == 0)
+		is_user = false;
+
+	systable_endscan(scan);
+	table_close(relation, AccessShareLock);
+
 	ReleaseSysCache(authtuple);
 
 	return is_user;