executor: fix query hang in IndexMerge Executor when it's killed (#45284)

[ti-chi-bot]

This is an automated cherry-pick of #45284

What problem does this PR solve?

Issue Number: close #45279

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

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

[xzhangxian1008]

/retest

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@79bb998). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-6.5     #45342   +/-   ##
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  Coverage               ?   73.8947%           
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  Files                  ?       1083           
  Lines                  ?     348366           
  Branches               ?          0           
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  Hits                   ?     257424           
  Misses                 ?      74486           
  Partials               ?      16456           

[windtalker]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: windtalker, XuHuaiyu

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-09 01:10:56.687824476 +0000 UTC m=+75021.236840460: ☑️ agreed by windtalker.
• 2023-08-09 02:06:09.36207602 +0000 UTC m=+78333.911092006: ☑️ agreed by XuHuaiyu.