scheduler: avoid to updateCounts frequently

[Leavrth]

What problem does this PR solve?

Issue Number: Close #7837

What is changed and how does it work?

Use O(1) method to update `counts`.

Check List

Tests

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

before PR, the speed of create operator decreased.

after PR

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• HuSharp
• rleungx

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[ti-chi-bot]

Hi @Leavrth. Thanks for your PR.

I'm waiting for a tikv member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[HuSharp]

/ok-to-test

[codecov]

Codecov Report

Merging #7836 (2981e0b) into master (e199866) will decrease coverage by 0.09%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7836      +/-   ##
==========================================
- Coverage   73.52%   73.44%   -0.09%     
==========================================
  Files         432      432              
  Lines       47937    47935       -2     
==========================================
- Hits        35248    35205      -43     
- Misses       9650     9688      +38     
- Partials     3039     3042       +3     

Flag	Coverage Δ
unittests	73.44% <100.00%> (-0.09%)	⬇️

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[HuSharp]

LGTM

[HuSharp]

/merge

[ti-chi-bot]

@HuSharp: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 2981e0b