ddl: gc mdl etcd key after cleaning the mdl table

[wjhuang2016]

Signed-off-by: wjhuang2016 huangwenjun1997@gmail.com

What problem does this PR solve?

Problem Summary:
We should gc mdl etcd key after cleaning the mdl table.
Otherwise, ddl may be blocked if the owner crash before cleaning the mdl table and the etcd key is gced

What is changed and how it works?

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:

• hawkingrei
• lcwangchao

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[hawkingrei]

/merge

[ti-chi-bot]

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

Details

Commit hash: 3a58b89

[wjhuang2016]

/run-all-tests

[wjhuang2016]

/run-all-tests

[wjhuang2016]

/run-unit-test

[sre-bot]

TiDB MergeCI notify

✅ Well Done! New fixed [1] after this pr merged.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci/integration-cdc-test	🔴 failed 2, success 38, total 40	24 min	Existing failure
idc-jenkins-ci-tidb/integration-ddl-test	✅ all 6 tests passed	4 min 43 sec	Fixed
idc-jenkins-ci-tidb/integration-common-test	🟢 all 17 tests passed	26 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 11 tests passed	10 min	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	6 min 4 sec	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	5 min 34 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	4 min 57 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 41 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 33 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed