planner: a better way to round scale factor when collecting TopN stats (#49808)

[ti-chi-bot]

This is an automated cherry-pick of #49808

What problem does this PR solve?

Issue Number: close #49801

Problem Summary: planner: a better way to round scale factor when collecting TopN stats

What changed and how does it work?

planner: a better way to round scale factor when collecting TopN stats

See #49801 for more details.

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

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.5@20c3e7d). Click here to learn what that means.
The diff coverage is 100.0000%.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #49821   +/-   ##
================================================
  Coverage               ?   72.4359%           
================================================
  Files                  ?       1404           
  Lines                  ?     411024           
  Branches               ?          0           
================================================
  Hits                   ?     297729           
  Misses                 ?      93746           
  Partials               ?      19549           

Flag	Coverage Δ
unit	72.4359% <100.0000%> (?)

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

Components	Coverage Δ
dumpling	53.9913% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.4466% <0.0000%> (?)

[fixdb]

+1

[qw4990]

/test check-dev2

[tiprow]

@qw4990: No presubmit jobs available for pingcap/[email protected]

In response to this:

/test check-dev2

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fixdb, qw4990

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• OWNERS [qw4990]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-02-20 04:06:29.280107337 +0000 UTC m=+330078.027730433: ☑️ agreed by fixdb.
• 2024-02-20 04:19:28.379441696 +0000 UTC m=+330857.127064804: ☑️ agreed by qw4990.

[qw4990]

/test mysql-test

[tiprow]

@qw4990: No presubmit jobs available for pingcap/[email protected]

In response to this:

/test mysql-test

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.

[purelind]

/retest