planner: fix unique key get wrong row count when to query the NULL value ｜tidb-test=pr/2400

[ti-chi-bot]

This is an automated cherry-pick of #56117

What problem does this PR solve?

Issue Number: close #56116

Problem Summary:

What changed and how does it work?

There will be issues with the row count under index/unique index. Previously, we would uniformly count the row count for this PointGet as 1, but if it is null, it will no longer be 1 and must be calculated according to the null count.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

From internal test cases

• 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

[hawkingrei]

/test all

[tiprow]

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

In response to this:

/test all

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[hawkingrei]

/retest

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 4 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-7.5@ac1493d). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #56191   +/-   ##
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  Coverage               ?   72.3655%           
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  Files                  ?       1413           
  Lines                  ?     413879           
  Branches               ?          0           
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  Hits                   ?     299506           
  Misses                 ?      94618           
  Partials               ?      19755           

Flag	Coverage Δ
unit	72.3655% <75.0000%> (?)

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

Components	Coverage Δ
dumpling	52.9400% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.5592% <0.0000%> (?)

[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:

• 2024-09-23 03:21:17.67137224 +0000 UTC m=+1449747.411796182: ☑️ agreed by hawkingrei.
• 2024-09-23 05:57:00.996991324 +0000 UTC m=+1459090.737415263: ☑️ agreed by qw4990.