server: replace instead of truncate encoded result

[xhebox]

What problem does this PR solve?

Issue Number: close #61085

Problem Summary: Change behavior when convert result.

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.

Fix bug that character_set_results will truncate instead of replace on error char

[tiprow]

Hi @xhebox. Thanks for your PR.

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[xhebox]

/ok-to-test

[xhebox]

/test all

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.7290%. Comparing base (c71ebaf) to head (c80d808).
Report is 34 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #61080        +/-   ##
================================================
+ Coverage   73.1307%   73.7290%   +0.5982%     
================================================
  Files          1724       1724                
  Lines        477081     485681      +8600     
================================================
+ Hits         348893     358088      +9195     
+ Misses       106761     106069       -692     
- Partials      21427      21524        +97     

Flag	Coverage Δ
integration	42.6020% <100.0000%> (?)
unit	72.6323% <100.0000%> (+0.2668%)	⬆️

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

Components	Coverage Δ
dumpling	52.7804% <ø> (ø)
parser	∅ <ø> (∅)
br	46.9379% <ø> (-0.6091%)	⬇️

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[xhebox]

/test mysql-test

[tiprow]

@xhebox: The specified target(s) for /test were not found.
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[bb7133]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bb7133, tangenta

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-05-15 03:24:57.296859776 +0000 UTC m=+588363.444821019: ☑️ agreed by tangenta.
• 2025-05-19 06:07:03.747421788 +0000 UTC m=+351990.003319175: ☑️ agreed by bb7133.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #61192.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #61193.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #61194.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #61195.