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

[YangKeao]

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

Merging #51586 (0e8e5d8) into master (87bcf32) will increase coverage by 2.3436%.
Report is 44 commits behind head on master.
The diff coverage is 100.0000%.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #51586        +/-   ##
================================================
+ Coverage   70.7575%   73.1012%   +2.3436%     
================================================
  Files          1467       1473         +6     
  Lines        436400     448203     +11803     
================================================
+ Hits         308786     327642     +18856     
+ Misses       108246     100356      -7890     
- Partials      19368      20205       +837     

Flag	Coverage Δ
integration	50.2926% <100.0000%> (?)
unit	70.4947% <50.0000%> (-0.0644%)	⬇️

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

Components	Coverage Δ
dumpling	53.9957% <ø> (ø)
parser	∅ <ø> (∅)
br	51.0436% <ø> (+5.1876%)	⬆️

[windtalker]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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

[LGTM Timeline notifier]

Timeline:

• 2024-03-07 10:13:18.96285344 +0000 UTC m=+334825.985099823: ☑️ agreed by xhebox.
• 2024-03-12 10:12:29.812375726 +0000 UTC m=+766776.834622114: ☑️ agreed by windtalker.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #52194.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #52195.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #52196.