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

All modified and coverable lines are covered by tests ✅

Project coverage is 55.7742%. Comparing base (e41a47c) to head (bf7918d).

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #53035         +/-   ##
=================================================
- Coverage   72.8332%   55.7742%   -17.0590%     
=================================================
  Files          1516       1638        +122     
  Lines        434792     606757     +171965     
=================================================
+ Hits         316673     338414      +21741     
- Misses        98528     245234     +146706     
- Partials      19591      23109       +3518     

Flag	Coverage Δ
integration	36.5145% <80.0000%> (?)

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

Components	Coverage Δ
dumpling	52.9656% <ø> (ø)
parser	∅ <ø> (∅)
br	52.6892% <ø> (+6.5835%)	⬆️

[ti-chi-bot]

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

In response to this:

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.

[terry1purcell]

/retest

[Rustin170506]

Thanks!

Some nits.

[Rustin170506]

Approve in advance.

Feel free to /unhold the PR after adding the test and comment.

/hold

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-04 03:01:28.619988623 +0000 UTC m=+3350242.377124196: ☑️ agreed by elsa0520.
• 2024-06-18 10:16:13.304829448 +0000 UTC m=+109899.790318280: ☑️ agreed by hi-rustin.

[Rustin170506]

/unhold

[Rustin170506]

Looks good to me. Thanks! 👍

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

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Needs approval from an approver in each of these files:

• OWNERS [elsa0520,hi-rustin]
• pkg/planner/OWNERS [elsa0520,hi-rustin]
• pkg/statistics/OWNERS [elsa0520,hi-rustin]

Approvers can indicate their approval by writing /approve in a comment
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[Rustin170506]

/retest