ddl: fix DDL schedule bug

[xiongjiwei]

Signed-off-by: xiongjiwei xiongjiwei1996@outlook.com

What problem does this PR solve?

Issue Number: close #38177

Problem Summary:

What is changed and how it works?

Check List

Tests

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

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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[hawkingrei]

/merge

[ti-chi-bot]

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

Commit hash: c0cd18e

[xiongjiwei]

/hold

[xiongjiwei]

/cc @wjhuang2016
PTAL

[xiongjiwei]

/unhold

[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-ddl-test	🟥 failed 3, success 3, total 6	25 min	New failing
idc-jenkins-ci-tidb/common-test	🔴 failed 1, success 10, total 11	9 min 34 sec	Existing failure
idc-jenkins-ci-tidb/tics-test	✅ all 1 tests passed	6 min 24 sec	Fixed
idc-jenkins-ci/integration-cdc-test	🟢 all 37 tests passed	26 min	Existing passed
idc-jenkins-ci-tidb/integration-common-test	🟢 all 17 tests passed	20 min	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	5 min 44 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	4 min 58 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 15 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	2 min 42 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed