planner: reduce topn count to exclude non-skewed values | tidb-test=pr/2333

[terry1purcell]

What problem does this PR solve?

Issue Number: close #53111

Problem Summary:

What changed and how does it work?

PR includes 3 changes to reduce unnecessary TopN values:

1. Reduce the default TopN to 100 (from 500).
2. Support pruning of TopN values that are "not skewed" for smaller tables.
3. And initially avoid adding values with a count=1 (which will be pruned anyway).

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]

Hi @terry1purcell. Thanks for your PR.

I'm waiting for a pingcap member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[hawkingrei]

/ok-to-test

[codecov]

Codecov Report

Attention: Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.

Project coverage is 52.7147%. Comparing base (1870d5f) to head (eebb721).

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #53035         +/-   ##
=================================================
- Coverage   74.5995%   52.7147%   -21.8849%     
=================================================
  Files          1508       1628        +120     
  Lines        358344     599772     +241428     
=================================================
+ Hits         267323     316168      +48845     
- Misses        71701     260604     +188903     
- Partials      19320      23000       +3680     

Flag	Coverage Δ
integration	37.1542% <78.5714%> (?)

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

Components	Coverage Δ
dumpling	55.1994% <ø> (ø)
parser	∅ <ø> (∅)
br	46.7301% <ø> (+2.8860%)	⬆️

[ti-chi-bot]

@ZL91: adding LGTM is restricted to approvers and reviewers in OWNERS files.

In response to this:

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[elsa0520]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: elsa0520, ZL91

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Needs approval from an approver in each of these files:

• OWNERS [elsa0520]
• pkg/planner/OWNERS [elsa0520]
• pkg/statistics/OWNERS [elsa0520]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-04 03:01:28.619988623 +0000 UTC m=+3350242.377124196: ☑️ agreed by elsa0520.

[winoros]

@time-and-fate I think you need to take a look at this line's change

[purelind]

/retest

[ti-chi-bot]

@terry1purcell: The following test 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/unit-test	eebb721	link	true	/test unit-test

Full PR test history. Your PR dashboard.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.