statistics: replace StatsLoad mutex with a dedicated mutex for statsCache protection

[Rustin170506]

What problem does this PR solve?

Issue Number: ref #55043

Problem Summary:

What changed and how does it work?

I moved the lock to the correct position because placing it near the two channels was too confusing.

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

All modified and coverable lines are covered by tests ✅

Project coverage is 73.5684%. Comparing base (8b30027) to head (ddb315b).
Report is 23 commits behind head on master.

Additional details and impacted files

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##             master     #59778        +/-   ##
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+ Coverage   72.9531%   73.5684%   +0.6152%     
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  Files          1699       1729        +30     
  Lines        469241     480686     +11445     
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+ Hits         342326     353633     +11307     
+ Misses       105828     105087       -741     
- Partials      21087      21966       +879     

Flag	Coverage Δ
integration	45.5950% <0.0000%> (?)
unit	72.1485% <100.0000%> (-0.0185%)	⬇️

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Components	Coverage Δ
dumpling	52.6910% <ø> (ø)
parser	∅ <ø> (∅)
br	44.3144% <ø> (-0.7391%)	⬇️

[Copilot]

PR Overview

This PR refactors mutex usage in the stats sync load logic by replacing the previously embedded mutex within StatsLoad with a dedicated mutex in statsSyncLoad to better protect the statsCache during concurrent updates.

• Introduces a dedicated mutex (mu) in statsSyncLoad.
• Updates updateCachedItem to use the new mutex.
• Removes the embedded mutex from the StatsLoad struct in types/interfaces.go.

Reviewed Changes

File	Description
pkg/statistics/handle/syncload/stats_syncload.go	Adds a dedicated mutex for protecting statsCache and updates lock usage
pkg/statistics/handle/types/interfaces.go	Removes the now-unneeded embedded sync.Mutex from the StatsLoad struct

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

PR Overview

This PR refactors mutex usage for protecting the statistics cache by introducing a dedicated mutex in the statsSyncLoad struct and removing the embedded mutex from the StatsLoad type.

• Introduced a dedicated mutex "mu" in statsSyncLoad for better clarity on protecting statsCache.
• Replaced locking on StatsLoad with locking on the dedicated mutex in updateCachedItem.
• Removed the unused embedded mutex from the StatsLoad type in interfaces.

Reviewed Changes

File	Description
pkg/statistics/handle/syncload/stats_syncload.go	Added a dedicated mutex for statsCache protection and updated locking
pkg/statistics/handle/types/interfaces.go	Removed an unnecessary embedded mutex from the StatsLoad type

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

pkg/statistics/handle/syncload/stats_syncload.go:70

• [nitpick] Consider renaming 'mu' to 'statsCacheMu' for enhanced clarity regarding its purpose.

mu sync.Mutex

[Rustin170506]

🔢 Self-check (PR reviewed by myself and ready for feedback.)

[elsa0520]

LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-03-03 05:43:36.20076835 +0000 UTC m=+247529.329688089: ☑️ agreed by elsa0520.
• 2025-03-03 05:53:30.05014607 +0000 UTC m=+248123.179065811: ☑️ agreed by AilinKid.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, elsa0520, qw4990

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• pkg/statistics/OWNERS [AilinKid,elsa0520,qw4990]

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