ddl: set context correctly in the setDDLLabelForDiagnosis (#40090)

[ti-chi-bot]

This is an automated cherry-pick of #40090

Signed-off-by: you06 you1474600@gmail.com

What problem does this PR solve?

Issue Number: close #40099

Problem Summary:

There is a fix in #36207, which may mistakely skip the init of context when the job context is not initialized in ddlCtx.setDDLLabelForDiagnosis.

What is changed and how it works?

This PR checks if the context is initialized before setting it, which also avoid the race.

» go test -race ./ddl -run TestAddIndex4
ok      github.com/pingcap/tidb/ddl     19.744s

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:

• CbcWestwolf
• cfzjywxk

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[wuhuizuo]

/hold high priority for trunk branch

[ti-chi-bot]

/unhold

[ti-chi-bot]

@CbcWestwolf: The /retest command does not accept any targets.
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• /test check-dev
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/retest build

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[CbcWestwolf]

/test build

[you06]

/hold

There is something strange that needs to be investigated.

[hawkingrei]

/merge

[ti-chi-bot]

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

Commit hash: 79d2945

[you06]

/retest

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@4d466ba). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-6.5     #40131   +/-   ##
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  Files                  ?       1083           
  Lines                  ?     376252           
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  Hits                   ?     291915           
  Misses                 ?      68997           
  Partials               ?      15340           

[you06]

/merge

[ti-chi-bot]

@you06: We have migrated to builtin LGTM and approve plugins for reviewing.

Please use /approve when you want approve this pull request.

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[you06]

/approve

[you06]

/lgtm

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CbcWestwolf, cfzjywxk, you06, zyguan

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Needs approval from an approver in each of these files:

• OWNERS [CbcWestwolf,cfzjywxk,you06,zyguan]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-16 16:23:04.495364238 +0000 UTC m=+734549.044380224: ☑️ agreed by you06.
• 2023-08-17 03:05:24.221119506 +0000 UTC m=+773088.770135493: ☑️ agreed by zyguan.