br: reduce memory usage when get incomplete ranges (#57192)

[ti-chi-bot]

This is an automated cherry-pick of #57192

What problem does this PR solve?

Issue Number: close #53529

Problem Summary:
it preallocates too much items and uses too much memory.

What changed and how does it work?

reduce the number of preallocated items

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

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-8.5@493a021). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.5     #57342   +/-   ##
================================================
  Coverage               ?   55.9769%           
================================================
  Files                  ?       1780           
  Lines                  ?     635286           
  Branches               ?          0           
================================================
  Hits                   ?     355614           
  Misses                 ?     255441           
  Partials               ?      24231           

Flag	Coverage Δ
integration	23.0321% <100.0000%> (?)
unit	72.4944% <100.0000%> (?)

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

Components	Coverage Δ
dumpling	52.9478% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	52.5649% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3pointer, Leavrth

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Needs approval from an approver in each of these files:

• br/OWNERS [3pointer,Leavrth]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-11-14 02:53:23.371950946 +0000 UTC m=+497565.562819940: ☑️ agreed by Leavrth.
• 2024-11-15 03:19:56.364107055 +0000 UTC m=+585558.554976052: ☑️ agreed by 3pointer.

[Leavrth]

/retest