ddl: refine BackendCtx.Flush to display Duplicate entry error

[lance6716]

What problem does this PR solve?

Issue Number: close #54184

Problem Summary:

easier to let Flush do error convertion. In the old code we still missed some branches that convert lightning error to ErrKeyExists

What changed and how does it work?

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

[tiprow]

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[codecov]

Codecov Report

Attention: Patch coverage is 58.33333% with 20 lines in your changes missing coverage. Please review.

Project coverage is 56.0958%. Comparing base (6695d5e) to head (4b5aa70).
Report is 9 commits behind head on master.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #54182         +/-   ##
=================================================
- Coverage   74.7738%   56.0958%   -18.6781%     
=================================================
  Files          1521       1644        +123     
  Lines        361185     617771     +256586     
=================================================
+ Hits         270072     346544      +76472     
- Misses        71477     247109     +175632     
- Partials      19636      24118       +4482     

Flag	Coverage Δ
integration	37.4279% <56.2500%> (?)
unit	71.9954% <18.7500%> (-1.6604%)	⬇️

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

Components	Coverage Δ
dumpling	52.9656% <ø> (-2.2339%)	⬇️
parser	∅ <ø> (∅)
br	53.1141% <ø> (+5.1435%)	⬆️

[lance6716]

/check-issue-triage-complete

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-24 12:45:37.183747966 +0000 UTC m=+637263.669236814: ☑️ agreed by tangenta.
• 2024-06-25 02:12:53.138925069 +0000 UTC m=+685699.624413894: ☑️ agreed by D3Hunter.