planner: Recognize potential for correlation in subset index match (WIP)

[terry1purcell]

What problem does this PR solve?

Issue Number: close #xxx

Problem Summary:

What changed and how does it work?

Collect the most selective predicate selectivity for multi-column indexes where there is a subset match and exponential backoff function is used for index selectivity/cardinality estimation. And use this in SkyLinePruning to improve rules for comparing index candidates.

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

[tiprow]

Hi @terry1purcell. Thanks for your PR.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.3351%. Comparing base (35f329d) to head (4c2a739).
Report is 2 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #58688        +/-   ##
================================================
+ Coverage   73.1026%   73.3351%   +0.2325%     
================================================
  Files          1677       1707        +30     
  Lines        463652     471629      +7977     
================================================
+ Hits         338942     345870      +6928     
- Misses       103883     104219       +336     
- Partials      20827      21540       +713     

Flag	Coverage Δ
integration	53.3043% <ø> (?)

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

Components	Coverage Δ
dumpling	52.6910% <ø> (ø)
parser	∅ <ø> (∅)
br	45.7616% <ø> (ø)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[ti-chi-bot]

[FORMAT CHECKER NOTIFICATION]

Notice: To remove the do-not-merge/needs-linked-issue label, please provide the linked issue number on one line in the PR body, for example: Issue Number: close #123 or Issue Number: ref #456.

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[ti-chi-bot]

@terry1purcell: 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	4c2a739	link	true	/test mysql-test
idc-jenkins-ci-tidb/check_dev	4c2a739	link	true	/test check-dev
idc-jenkins-ci-tidb/check_dev_2	4c2a739	link	true	/test check-dev2
idc-jenkins-ci-tidb/unit-test	4c2a739	link	true	/test unit-test

Full PR test history. Your PR dashboard.

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