unstable DM-123

[lance6716]

Which jobs are flaking?

DM-IT

Which test(s) are flaking?

DM-123

Jenkins logs or GitHub Actions link

[2022-08-02T11:02:28.919Z] Comparing the table structure of ``shardddl`.`tb`` ... failure

https://ci2.pingcap.net/blue/organizations/jenkins/dm_ghpr_integration_test/detail/dm_ghpr_integration_test/8490/pipeline/

Anything else we need to know

• Does this test exist for other branches as well?

• Has there been a high frequency of failure lately?

[lance6716]

related to https://github.com/pingcap/tiflow/issues/3790

Worker1 is not the last worker, it received "drop index idx1, drop index idx2" Worker2 is the last worker, it received "drop index idx1, add index idx1(...), drop index idx2, add index idx2(...)"

But worker1 runs too slowly, its "drop index idx1" actually drops the new idx1 which worker2 just created.

/cc @GMHDBJD