planner: Ensure index without stats survives for skyling pruning | tidb-test=pr/2465 (#58729)

[ti-chi-bot]

This is an automated cherry-pick of #58729

What problem does this PR solve?

Issue Number: close #57948

Problem Summary:

What changed and how does it work?

Enhanced CompareCandidates logic within SkyLinePruning to allow an index without statistics to survive so that it can be preferenced above a tablescan if it has more equals predicates than other available choices.

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.

None

[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

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[ti-chi-bot]

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[codecov]

Codecov Report

Attention: Patch coverage is 61.62791% with 33 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-8.5@5009853). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.5     #59227   +/-   ##
================================================
  Coverage               ?   22.7886%           
================================================
  Files                  ?       1670           
  Lines                  ?     611388           
  Branches               ?          0           
================================================
  Hits                   ?     139327           
  Misses                 ?     454463           
  Partials               ?      17598           

Flag	Coverage Δ
integration	22.7886% <61.6279%> (?)

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

Components	Coverage Δ
dumpling	∅ <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	22.9875% <0.0000%> (?)

[ti-chi-bot]

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/mysql-test	f815476	link	true	/test mysql-test
idc-jenkins-ci-tidb/check_dev	f815476	link	true	/test check-dev
idc-jenkins-ci-tidb/unit-test	f815476	link	true	/test unit-test

Full PR test history. Your PR dashboard.

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