text: -- @Description Ensures that an update during a vacuum operation is ok
  -- 
  
  DELETE FROM ao WHERE a < 128;
  4: BEGIN;
  4: SELECT COUNT(*) FROM ao;
  5: BEGIN;
  4: SELECT COUNT(*) FROM ao;
  4: BEGIN;
  4: SELECT COUNT(*) FROM ao;
  2>: VACUUM ao;
  4: SELECT COUNT(*) FROM ao;SELECT COUNT(*) FROM ao;BEGIN;UPDATE ao SET b=1 WHERE a > 500;UPDATE ao SET b=1 WHERE a > 400;COMMIT;
  2<:
  3: SELECT COUNT(*) FROM ao WHERE b = 1;
  3: INSERT INTO ao VALUES (0);
  