*: backport dynamic parameter change for DXF add index to 8.5

[joechenrh]

What problem does this PR solve?

Issue Number: ref https://github.com/pingcap/tidb/issues/57497, close #64947

Problem Summary:

Manually pick dynamic parameter change related PR, including

• All PRs in https://github.com/pingcap/tidb/pull/62083
• https://github.com/pingcap/tidb/pull/57770
• https://github.com/pingcap/tidb/pull/59165
• https://github.com/pingcap/tidb/pull/59046
• https://github.com/pingcap/tidb/pull/59343
• https://github.com/pingcap/tidb/pull/60677
• https://github.com/pingcap/tidb/pull/62084
• https://github.com/pingcap/tidb/pull/62120

What changed and how does it work?

Check List

Tests

• [x] Unit test
• [x] 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

[tiprow[bot]]

Hi @joechenrh. Thanks for your PR.

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[codecov[bot]]

Codecov Report

:x: Patch coverage is 86.13078% with 333 lines in your changes missing coverage. Please review. :warning: Please upload report for BASE (release-8.5@0c9f23f). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.5     #64930   +/-   ##
================================================
  Coverage               ?   77.0996%           
================================================
  Files                  ?       1684           
  Lines                  ?     468356           
  Branches               ?          0           
================================================
  Hits                   ?     361101           
  Misses                 ?      85036           
  Partials               ?      22219           

Flag	Coverage Δ
integration	50.9676% <63.3486%> (?)
unit	72.1415% <69.7868%> (?)

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

Components	Coverage Δ
dumpling	52.9278% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	65.1898% <0.0000%> (?)

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[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2025-12-10 06:07:38.291512445 +0000 UTC m=+1021203.105290017: :ballot_box_with_check: agreed by Benjamin2037.
• 2025-12-11 07:06:23.221856841 +0000 UTC m=+1111128.035634412: :ballot_box_with_check: agreed by D3Hunter.

[joechenrh]

/hold Let me do some tests, since it's not a "small" cherry-pick.

[joechenrh]

/retest

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[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

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

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• ~~OWNERS~~ [Benjamin2037,D3Hunter,Leavrth]
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• ~~pkg/ddl/OWNERS~~ [Benjamin2037,D3Hunter]
• ~~pkg/disttask/OWNERS~~ [Benjamin2037,D3Hunter]
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• ~~pkg/lightning/OWNERS~~ [Benjamin2037,D3Hunter]
• ~~pkg/meta/OWNERS~~ [Benjamin2037,D3Hunter]
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[joechenrh]

/unhold

I've pasted some of the test result based on this PR in the description.

[joechenrh]

/retest

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

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[lance6716]

/retest

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@lance6716: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

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