statistics: merge global stats even if some partition stats are missing

[xuyifangreeneyes]

What problem does this PR solve?

Issue Number: ref #38999

Problem Summary:

What is changed and how it works?

Introduce a system variable tidb_skip_missing_partition_stats, whose default value is on. If tidb_skip_missing_partition_stats turns on, merging global stats would skip partitions whose stats are missing rather than fail.

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

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[hawkingrei]

@xuyifangreeneyes Please fix the conflict.

[chrysan]

please add tests

[chrysan]

Do we need to remove the count adding later in this func?

[xuyifangreeneyes]

Yes. It is a mistake I made when resolving conflicts.

[codecov]

Codecov Report

Attention: Patch coverage is 65.88235% with 29 lines in your changes missing coverage. Please review.

Project coverage is 73.2481%. Comparing base (c0459da) to head (cf303f7).
Report is 3847 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #41176        +/-   ##
================================================
+ Coverage   73.2404%   73.2481%   +0.0076%     
================================================
  Files          1267       1270         +3     
  Lines        389943     390679       +736     
================================================
+ Hits         285596     286165       +569     
- Misses        86048      86170       +122     
- Partials      18299      18344        +45     

Flag	Coverage Δ
integration	78.1388% <ø> (?)
unit	73.2396% <65.8823%> (-0.0009%)	⬇️

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

Components	Coverage Δ
dumpling	54.0444% <ø> (ø)
parser	85.0663% <ø> (+0.0109%)	⬆️
br	52.1472% <ø> (+0.0462%)	⬆️

[xuyifangreeneyes]

/test check-dev

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@xuyifangreeneyes: The specified target(s) for /test were not found.
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[xuyifangreeneyes]

/test build

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[xuyifangreeneyes]

/unhold

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[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

@xuyifangreeneyes: 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	cf303f7	link	unknown	/test unit-test

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[xuyifangreeneyes]

/test unit-test

[tiprow]

@xuyifangreeneyes: The specified target(s) for /test were not found.
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Use /test all to run all jobs.

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/test unit-test

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #49471.

[ti-chi-bot]

In response to a cherrypick label: new pull request could not be created: failed to create pull request against pingcap/tidb#release-7.1 from head ti-chi-bot:cherry-pick-41176-to-release-7.1: the GitHub API request returns a 403 error: {"message":"You have exceeded a secondary rate limit and have been temporarily blocked from content creation. Please retry your request again later. If you reach out to GitHub Support for help, please include the request ID ACA6:3F108B:1B81993:33D55A3:671F467B and timestamp 2024-10-28 08:08:27 UTC.","documentation_url":"https://docs.github.com/rest/overview/rate-limits-for-the-rest-api#about-secondary-rate-limits","status":"403"}

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #57146.