ddl: set a lower limit of regions for distributed local sort

[tangenta]

What problem does this PR solve?

Issue Number: close #56501

Problem Summary: See #56501

What changed and how does it work?

// Assuming the region size is 96MiB and the index data size accounts for 1/10 of the row data.
// Row data take 960GiB for 10000 regions, and index data take 96GiB.
// This basically matches the default value of tidb_ddl_disk_quota.
// Estimates don't necessarily have to be accurate.

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]

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[tiprow]

Hi @tangenta. Thanks for your PR.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.8873%. Comparing base (025c2a3) to head (a01a9fd).

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #56613         +/-   ##
=================================================
- Coverage   73.3320%   56.8873%   -16.4448%     
=================================================
  Files          1629       1778        +149     
  Lines        449708     636548     +186840     
=================================================
+ Hits         329780     362115      +32335     
- Misses        99711     249520     +149809     
- Partials      20217      24913       +4696     

Flag	Coverage Δ
integration	39.0058% <100.0000%> (?)

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Components	Coverage Δ
dumpling	52.9478% <ø> (ø)
parser	∅ <ø> (∅)
br	63.1671% <ø> (+17.5756%)	⬆️

[ti-chi-bot]

@tangenta: 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
pull-unit-test-ddlv1	a01a9fd	link	true	/test pull-unit-test-ddlv1
idc-jenkins-ci-tidb/unit-test	a01a9fd	link	true	/test unit-test

Full PR test history. Your PR dashboard.

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