executor: do not acqurie pessimistic lock for non-unique index keys (#36229)

[ti-srebot]

cherry-pick #36229 to release-5.3
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/36557

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/36557:release-5.3-87c5b5068ab8

---

Signed-off-by: ekexium eke@fastmail.com

What problem does this PR solve?

Issue Number: close #36235

Problem Summary:

Fix the condition of checking if the index KV is unique or not.

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.

bugfix: do not acquire pessimistic lock for non-unique index keys

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• tiancaiamao

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[ti-chi-bot]

@ti-srebot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick, it must first be approved by the collaborators.

AFTER it has been approved by collaborators, please ping the release team in a comment to request a cherry pick review.

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[ti-srebot]

/run-all-tests

[ti-srebot]

@ekexium you're already a collaborator in bot's repo.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/71cdb094f94343ff685a1add4f3bef83f48d5c9a

[ekexium]

PTAL guys @tiancaiamao @wjhuang2016

[codecov]

Codecov Report

Merging #36557 (71cdb09) into release-5.3 (e6c3d7a) will not change coverage.
Report is 36 commits behind head on release-5.3.
The diff coverage is n/a.

Additional details and impacted files

@@              Coverage Diff               @@
##           release-5.3     #36557   +/-   ##
==============================================
  Coverage      53.3571%   53.3571%           
==============================================
  Files               19         19           
  Lines             3366       3366           
==============================================
  Hits              1796       1796           
  Misses            1421       1421           
  Partials           149        149           

[ti-chi-bot]

This pull request is closed because its related version has closed automatic cherry-picking.
If it's still needed, you can reopen it or just regenerate it using bot,
see:

https://prow.tidb.net/command-help#cherrypick
https://book.prow.tidb.net/#/plugins/cherrypicker