planner: adjust N used in TopN cost formula based on the total number of rows (#46368)

[ti-chi-bot]

This is an automated cherry-pick of #46368

What problem does this PR solve?

Issue Number: close #43285

Problem Summary: planner: adjust N used in TopN cost formula based on the total number of rows

What is changed and how it works?

planner: adjust N used in TopN cost formula based on the total number of rows

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

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]

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Adding the do-not-merge/cherry-pick-not-approved label.

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-10-19 07:58:12.403511627 +0000 UTC m=+1903089.990621768: ☑️ agreed by qw4990.
• 2023-10-19 07:58:36.694746094 +0000 UTC m=+1903114.281856241: ☑️ agreed by hawkingrei.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@d7ce2f2). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

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##             release-6.5     #46570   +/-   ##
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