statistics: fix the potential error when merging global stats

[winoros]

What problem does this PR solve?

Issue Number: close #52251

Problem Summary:

It's another way compared with https://github.com/pingcap/tidb/pull/52122. This one should be better to solve problems.

What changed and how does it work?

See the changed tests to know the error of the previous codes.

Check List

Tests

• [x] 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[bot]]

Codecov Report

Attention: Patch coverage is 68.98734% with 49 lines in your changes missing coverage. Please review.

Project coverage is 73.6557%. Comparing base (32d11a8) to head (7458306). Report is 40 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #52218        +/-   ##
================================================
+ Coverage   73.0104%   73.6557%   +0.6452%     
================================================
  Files          1683       1714        +31     
  Lines        466007     477399     +11392     
================================================
+ Hits         340234     351632     +11398     
+ Misses       104833     104004       -829     
- Partials      20940      21763       +823     

Flag	Coverage Δ
integration	45.5886% <35.4430%> (?)
unit	72.2486% <68.9873%> (+0.0457%)	:arrow_up:

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

Components	Coverage Δ
dumpling	52.6910% <ø> (ø)
parser	∅ <ø> (∅)
br	44.6415% <ø> (-0.6761%)	:arrow_down:

[hawkingrei]

/retest

[ti-chi-bot[bot]]

PR needs rebase.

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

[winoros]

/retest

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, time-and-fate

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

The pull request process is described here

Needs approval from an approver in each of these files:

• ~~OWNERS~~ [hawkingrei,time-and-fate]
• ~~pkg/statistics/OWNERS~~ [hawkingrei,time-and-fate]

Approvers can indicate their approval by writing /approve in a comment Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-03-29 10:45:03.271240684 +0000 UTC m=+8764.798781232: :ballot_box_with_check: agreed by hawkingrei.
• 2025-01-22 08:01:35.696952038 +0000 UTC m=+254223.027871453: :ballot_box_with_check: agreed by time-and-fate.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #59125.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #59174.