statistics: allow tidb_merge_partition_stats_concurrency to take effect immediately

[hawkingrei]

…g merge global stats

What problem does this PR solve?

Issue Number: close #47919

Problem Summary:

What is changed and how it works?

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

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[codecov[bot]]

Codecov Report

:x: Patch coverage is 45.45455% with 6 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 72.7957%. Comparing base (d1fc638) to head (e7c86c5). :warning: Report is 5119 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #47913        +/-   ##
================================================
+ Coverage   71.6271%   72.7957%   +1.1686%     
================================================
  Files          1401       1421        +20     
  Lines        405768     411473      +5705     
================================================
+ Hits         290640     299535      +8895     
+ Misses        95337      93076      -2261     
+ Partials      19791      18862       -929     

Flag	Coverage Δ
integration	32.9878% <27.2727%> (?)
unit	77.5917% <45.4545%> (+5.9646%)	:arrow_up:

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

Components	Coverage Δ
dumpling	∅ <ø> (∅)
parser	∅ <ø> (∅)
br	77.1466% <ø> (+24.1203%)	:arrow_up:

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[winoros]

The result should still be better than 7.1. So we merge it first.

[hawkingrei]

/test all

[tiprow[bot]]

@hawkingrei: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
tiprow_fast_test	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test tiprow_fast_test

Full PR test history. Your PR dashboard.

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[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.

[ti-chi-bot[bot]]

@hawkingrei: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/mysql-test	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test mysql-test
pull-mysql-client-test	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test pull-mysql-client-test
idc-jenkins-ci-tidb/check_dev_2	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test check-dev2
idc-jenkins-ci-tidb/unit-test	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test unit-test
idc-jenkins-ci-tidb/build	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test build
idc-jenkins-ci-tidb/check_dev	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test check-dev
pull-integration-ddl-test	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test pull-integration-ddl-test
pull-br-integration-test	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test pull-br-integration-test
pull-lightning-integration-test	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test pull-lightning-integration-test
pull-integration-e2e-test	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test pull-integration-e2e-test
pull-integration-realcluster-test-next-gen	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test pull-integration-realcluster-test-next-gen
pull-unit-test-next-gen	e7c86c50bff8da8e076b0e31923ff4cf7671b635	link	true	/test pull-unit-test-next-gen

Full PR test history. Your PR dashboard.

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-sigs/prow repository. I understand the commands that are listed here.