importinto: disable switching to 'import mode' when global sort (#60363) | tidb-test=release-8.1.2

[ti-chi-bot]

This is an automated cherry-pick of #60363

What problem does this PR solve?

Issue Number: close #60361

Problem Summary:

What changed and how does it work?

disable switch to import mode when using global sort, no change for local sort

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]

@D3Hunter This PR has conflicts, I have hold it.
Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[Benjamin2037]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Benjamin2037, D3Hunter

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Needs approval from an approver in each of these files:

• OWNERS [Benjamin2037,D3Hunter]
• pkg/executor/importer/OWNERS [D3Hunter]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-04-02 12:56:50.80545872 +0000 UTC m=+1656304.489694816: ☑️ agreed by Benjamin2037.
• 2025-04-02 12:57:10.138248445 +0000 UTC m=+1656323.822484541: ☑️ agreed by D3Hunter.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (feature/release-8.1-gsort-test@0162dfa). Learn more about missing BASE report.

Additional details and impacted files

@@                         Coverage Diff                         @@
##             feature/release-8.1-gsort-test     #60379   +/-   ##
===================================================================
  Coverage                                  ?   71.1999%           
===================================================================
  Files                                     ?       1469           
  Lines                                     ?     424503           
  Branches                                  ?          0           
===================================================================
  Hits                                      ?     302246           
  Misses                                    ?     101682           
  Partials                                  ?      20575           

Flag	Coverage Δ
unit	71.1999% <100.0000%> (?)

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

Components	Coverage Δ
dumpling	52.9656% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	41.5268% <0.0000%> (?)

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