planner: optimize performance of IndexUsage utilities (#53195)

[ti-chi-bot]

This is an automated cherry-pick of #53195

What problem does this PR solve?

Issue Number: close #51898

Problem Summary:

This PR is trying to optimize the performance of IndexUsage utilities. Previously it costed around 1% CPU and did a lot of allocation. This PR tries to optimize it and get some tiny performance boost.

What changed and how does it work?

1. Add a pool to avoid frequently allocating/de-allocating indexUsage and the internal entries.
2. Avoid using getTblInfoForUsedStatsByPhysicalID, which is very slow because it iterates over all tables.

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.

I used https://gist.github.com/YangKeao/c02ada99d2602d5e7fb5fb94f0581015 to run a stabler select_random_points benchmark. It gives QPS 59029 and 58393 for the commit before index usage and with index usage enabled.

After patching the index usage commit with this PR, the average QPS goes to 58854. I'm not sure whether there are other spaces to improve the performance (like improving the speed of loading stats).

As a reference: the flamegraph before this PR:

The flamegraph after this PR:

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

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 8 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (release-8.1@a1c1451). Click here to learn what that means.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.1     #53215   +/-   ##
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  Coverage               ?   71.2724%           
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Flag	Coverage Δ
unit	71.2724% <75.0000%> (?)

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

Components	Coverage Δ
dumpling	53.9957% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	40.9772% <0.0000%> (?)

[YangKeao]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, YangKeao

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• OWNERS [YangKeao,hawkingrei]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-13 04:47:42.943345623 +0000 UTC m=+1455816.700481195: ☑️ agreed by hawkingrei.
• 2024-05-13 05:58:58.899731275 +0000 UTC m=+1460092.656866842: ☑️ agreed by YangKeao.