statistics: fix async merge global stats use cmsketch twice

[L-maple]

What problem does this PR solve?

Issue Number: close #59194

Problem Summary:
the same cmsketch is merge twice, which affects row estimation.

What changed and how does it work?

remove the unnecessary part.

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

[ti-chi-bot]

Hi @L-maple. Thanks for your PR.

I'm waiting for a pingcap 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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[tiprow]

Hi @L-maple. Thanks for your PR.

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[L-maple]

/assign @L-maple

[hawkingrei]

/ok-to-test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.7246%. Comparing base (ba79f50) to head (53e008d).
Report is 28 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #59198        +/-   ##
================================================
+ Coverage   73.0012%   73.7246%   +0.7233%     
================================================
  Files          1684       1719        +35     
  Lines        466236     488434     +22198     
================================================
+ Hits         340358     360096     +19738     
- Misses       104917     105993      +1076     
- Partials      20961      22345      +1384     

Flag	Coverage Δ
integration	45.6431% <ø> (?)
unit	72.3136% <ø> (+0.1218%)	⬆️

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	44.8053% <ø> (-0.5064%)	⬇️

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, winoros

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Needs approval from an approver in each of these files:

• pkg/statistics/OWNERS [hawkingrei,winoros]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-01-24 10:48:12.277474109 +0000 UTC m=+437019.608393516: ☑️ agreed by winoros.
• 2025-01-25 02:10:42.875011427 +0000 UTC m=+492370.205930831: ☑️ agreed by hawkingrei.

[hawkingrei]

/cherrypick release-8.5
/cherrypick release-8.1
/cherrypick release-7.5

[ti-chi-bot]

@hawkingrei: new pull request created to branch release-7.5: #59207.

In response to this:

/cherrypick release-8.5
/cherrypick release-8.1
/cherrypick release-7.5

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 ti-community-infra/tichi repository.

[ti-chi-bot]

@hawkingrei: new pull request created to branch release-8.1: #59208.

In response to this:

/cherrypick release-8.5
/cherrypick release-8.1
/cherrypick release-7.5

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 ti-community-infra/tichi repository.

[ti-chi-bot]

@hawkingrei: new pull request created to branch release-8.5: #59209.

In response to this:

/cherrypick release-8.5
/cherrypick release-8.1
/cherrypick release-7.5

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 ti-community-infra/tichi repository.