importinto: calculate distsql scan concurency in nextgen

[D3Hunter]

What problem does this PR solve?

Issue Number: ref #61702

Problem Summary:

What changed and how does it work?

then we can make the checksum step faster, and don't need user to set it.

Check List

Tests

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

import 100G data locally, see it's 60

[2025/09/02 19:29:36.495 +08:00] [INFO] [import.go:1322] ["set import thread count for nextgen kernel"] [keyspaceName=SYSTEM] [table=sys] ["thread count"=4] ["max node count"=1] ["target node cpu count"=10] ["dist sql scan concurrency"=60] ["total file size"=100GiB]

import 100T, it's 281

[2025/09/02 19:42:52.314 +08:00] [INFO] [import.go:1322] ["set import thread count for nextgen kernel"] [keyspaceName=SYSTEM] [table=sys] ["thread count"=10] ["max node count"=25] ["dist sql scan concurrency"=281] ["target node cpu count"=10] ["total file size"=100TiB]

• 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

[tiprow]

Hi @D3Hunter. Thanks for your PR.

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[codecov]

Codecov Report

❌ Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.2699%. Comparing base (3d9a0eb) to head (b7dd28b).
⚠️ Report is 12 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #63341        +/-   ##
================================================
+ Coverage   72.7832%   73.2699%   +0.4866%     
================================================
  Files          1832       1832                
  Lines        495794     496175       +381     
================================================
+ Hits         360855     363547      +2692     
+ Misses       113010     110782      -2228     
+ Partials      21929      21846        -83     

Flag	Coverage Δ
integration	42.0275% <0.0000%> (?)
unit	72.3279% <76.9230%> (+0.0759%)	⬆️

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Components	Coverage Δ
dumpling	52.8700% <ø> (ø)
parser	∅ <ø> (∅)
br	46.5345% <ø> (+0.0025%)	⬆️

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[D3Hunter]

/retest

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[D3Hunter]

/retest

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[D3Hunter]

/cherry-pick release-nextgen-20250815

[ti-chi-bot]

@D3Hunter: once the present PR merges, I will cherry-pick it on top of release-nextgen-20250815 in the new PR and assign it to you.

In response to this:

/cherry-pick release-nextgen-20250815

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: GMHDBJD, wjhuang2016

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-09-03 04:46:48.935298854 +0000 UTC m=+933900.813129808: ☑️ agreed by GMHDBJD.
• 2025-09-03 09:18:36.094517873 +0000 UTC m=+950207.972348817: ☑️ agreed by wjhuang2016.

[D3Hunter]

/retest

[tiprow]

@D3Hunter: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

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[ti-chi-bot]

@D3Hunter: new pull request created to branch release-nextgen-20250815: #63362.

In response to this:

/cherry-pick release-nextgen-20250815

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