fix citusdata#7647 Add tests, add order by for test

src/test/regress/sql/columnar_join.sql

@@ -153,8 +153,9 @@ INSERT INTO tbl_cross_columnar VALUES (4, 40), (5, 50), (6, 60);
 
 SELECT h.id AS heap_id, h.val AS heap_val, c.id AS columnar_id, c.val AS columnar_val
 FROM tbl_cross_heap h
-CROSS JOIN tbl_cross_columnar c;
+CROSS JOIN tbl_cross_columnar c
+ORDER BY 3,4,1,2;
 
 -- End test case
 SET client_min_messages TO warning;
-DROP SCHEMA am_columnar_join CASCADE;
+DROP SCHEMA am_columnar_join CASCADE;