ddl: stabilize multi-schema change tests

[tangenta]

What problem does this PR solve?

Issue Number: close #39224

Problem Summary:

It is possible that the last DDL job does not exit in time.

What is changed and how it works?

Skip non-multi-schema change jobs.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• Defined2014
• hawkingrei

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[Defined2014]

Don't understand why it happend. When create table t return, it means the ddl job is finished. Why it possible the last DDL job not exit?

[tangenta]

Imagine that the DDL frontend ticks(case <-ticker.C:) immediately after a DDL worker commits the transaction that writes rows to tidb_ddl_history in HandleJobDone(). Even though the result is successfully returned to the client, the hook OnUpdate() is not called yet.

[tangenta]

/run-check-issue-triage-complete

[hawkingrei]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: e2a8023

[sre-bot]

TiDB MergeCI notify

🔴 Bad News! New failing [1] after this pr merged.
These new failed integration tests seem to be caused by the current PR, please try to fix these new failed integration tests, thanks!

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-common-test	🟥 failed 1, success 16, total 17	14 min	New failing
idc-jenkins-ci/integration-cdc-test	🔴 failed 1, success 38, total 39	23 min	Existing failure
idc-jenkins-ci-tidb/mybatis-test	🔴 failed 1, success 0, total 1	11 min	Existing failure
idc-jenkins-ci-tidb/common-test	🟢 all 11 tests passed	10 min	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	5 min 41 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	5 min 12 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	4 min 55 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	4 min 44 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 14 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed