Backup: remove improper memory usage during full backup (#58591)

[ti-chi-bot]

This is an automated cherry-pick of #58591

What problem does this PR solve?

Issue Number: close #58587
Problem Summary:
When performing a full backup on millions of tables, the default incomplete range buffer grows significantly due to the large number of ranges. Since most ranges are complete, a lower buffer value should be used to optimize memory usage.

What changed and how does it work?

Set default incomplete to a lower value.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  Manually Backup millions of tables
  Before this PR, the inuse memory consume 4GB with GetIncompleteRanges
  

After the memory usage reduced.

• 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@84f6a9a). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.5     #59500   +/-   ##
================================================
  Coverage               ?   58.9105%           
================================================
  Files                  ?       1777           
  Lines                  ?     654048           
  Branches               ?          0           
================================================
  Hits                   ?     385303           
  Misses                 ?     244095           
  Partials               ?      24650           

Flag	Coverage Δ
integration	40.7980% <100.0000%> (?)
unit	72.7816% <100.0000%> (?)

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

Components	Coverage Δ
dumpling	52.9278% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	64.2134% <0.0000%> (?)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• br/OWNERS [3pointer,Leavrth]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-02-13 08:57:34.617936281 +0000 UTC m=+519697.014158343: ☑️ agreed by Leavrth.
• 2025-02-13 09:58:57.431769655 +0000 UTC m=+523379.827991719: ☑️ agreed by 3pointer.

[3pointer]

/test unit-test

[tiprow]

@3pointer: No presubmit jobs available for pingcap/[email protected]

Details

In response to this:

/test unit-test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[BornChanger]

/retest

[3pointer]

/test unit-test

[tiprow]

@3pointer: No presubmit jobs available for pingcap/[email protected]

Details

In response to this:

/test unit-test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[BornChanger]

/retest

[3pointer]

/test unit-test

[tiprow]

@3pointer: No presubmit jobs available for pingcap/[email protected]

Details

In response to this:

/test unit-test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[3pointer]

/test unit-test

[tiprow]

@3pointer: No presubmit jobs available for pingcap/[email protected]

Details

In response to this:

/test unit-test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[3pointer]

/test unit-test

//pkg/session:session_test not stable

[tiprow]

@3pointer: No presubmit jobs available for pingcap/[email protected]

Details

In response to this:

/test unit-test

//pkg/session:session_test not stable

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[3pointer]

/retest

[3pointer]

/retest