planner: small refactor for plan cache

[qw4990]

What problem does this PR solve?

Issue Number: ref #50618

Problem Summary: planner: small refactor for plan cache

What changed and how does it work?

planner: small refactor for plan cache

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 74.1644%. Comparing base (516977e) to head (83103c1).
Report is 2 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #53028        +/-   ##
================================================
+ Coverage   72.0377%   74.1644%   +2.1266%     
================================================
  Files          1499       1499                
  Lines        431246     431282        +36     
================================================
+ Hits         310660     319858      +9198     
+ Misses       101286      91598      -9688     
- Partials      19300      19826       +526     

Flag	Coverage Δ
integration	49.0318% <100.0000%> (?)
unit	71.2662% <100.0000%> (+0.0117%)	⬆️

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

Components	Coverage Δ
dumpling	53.9957% <ø> (ø)
parser	∅ <ø> (∅)
br	46.5726% <ø> (+8.2205%)	⬆️

[hi-rustin]

Looks good to me. Thanks! 👍

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-06 08:21:45.790532715 +0000 UTC m=+863859.547668280: ☑️ agreed by hawkingrei.
• 2024-05-06 08:23:30.817797231 +0000 UTC m=+863964.574932804: ☑️ agreed by hi-rustin.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, hawkingrei, hi-rustin, XuHuaiyu

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Needs approval from an approver in each of these files:

• OWNERS [AilinKid,XuHuaiyu,hawkingrei,hi-rustin]
• pkg/expression/OWNERS [XuHuaiyu]
• pkg/planner/OWNERS [AilinKid,hawkingrei,hi-rustin]

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