json: don't resize slice to get extra zero when the length is unspecified (#51586)

[ti-chi-bot]

This is an automated cherry-pick of #51586

What problem does this PR solve?

Issue Number: close #51547

Problem Summary:

What changed and how does it work?

If the flen of a binary string is unspecified, don't resize the target json opaque.

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

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 lines in your changes are missing coverage. Please review.

Please upload report for BASE (release-7.5@e921620). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #52196   +/-   ##
================================================
  Coverage               ?   72.1915%           
================================================
  Files                  ?       1411           
  Lines                  ?     411191           
  Branches               ?          0           
================================================
  Hits                   ?     296845           
  Misses                 ?      94557           
  Partials               ?      19789           

Flag	Coverage Δ
unit	72.1915% <50.0000%> (?)

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

Components	Coverage Δ
dumpling	53.9913% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.4919% <0.0000%> (?)

[windtalker]

LGTM

[YangKeao]

/retest

[YangKeao]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: windtalker, YangKeao

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• OWNERS [YangKeao,windtalker]
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-21 09:42:37.732041803 +0000 UTC m=+2164711.489177376: ☑️ agreed by windtalker.
• 2024-05-21 13:31:05.515381599 +0000 UTC m=+2178419.272517171: ☑️ agreed by YangKeao.