planner: fix index merge shouldn't push partial limit down when index plans are keep ordered (#52979)

[ti-chi-bot]

This is an automated cherry-pick of #52979

What problem does this PR solve?

Issue Number: close #52947

Problem Summary:
#52947 (comment)

What changed and how does it work?

Check List

Tests

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

  • I checked and no code files have been changed.

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.

planner: fix index merge shouldn't push partial limit down when index plans are keep ordered

[fixdb]

+1

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, fixdb

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-28 04:42:40.351887507 +0000 UTC m=+2751514.109023079: ☑️ agreed by fixdb.
• 2024-05-28 07:39:31.018336927 +0000 UTC m=+2762124.775472500: ☑️ agreed by AilinKid.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-7.5@2c3afb7). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #53417   +/-   ##
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  Coverage               ?   72.1632%           
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  Files                  ?       1411           
  Lines                  ?     411391           
  Branches               ?          0           
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  Hits                   ?     296873           
  Misses                 ?      94707           
  Partials               ?      19811           

Flag	Coverage Δ
unit	72.1632% <100.0000%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	53.9913% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.5051% <0.0000%> (?)

[AilinKid]

/test check-dev2

[tiprow]

@AilinKid: No presubmit jobs available for pingcap/[email protected]

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/test check-dev2

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