globalsort: split files evenly in MergeOverlappingFiles

[D3Hunter]

What problem does this PR solve?

Issue Number: ref #50752

Problem Summary:

What changed and how does it work?

try to split files more evenly to improve performance

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

before(import 1.194TiB with force merge step)

[step=merge-sort] [mem-limit-percent=0.99] [server-mem-limit=88%] [resource="[CPU=16, Mem=27.83GiB]"] [takeTime=31m43.024898826s] []

after(about 2~3 minutes improvement)

[step=merge-sort] [mem-limit-percent=0.99] [server-mem-limit=88%] [resource="[CPU=16, Mem=27.83GiB]"] [takeTime=28m39.158921948s]

• 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

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[codecov]

Codecov Report

Merging #51878 (cf43e67) into master (7056209) will decrease coverage by 15.9852%.
Report is 7 commits behind head on master.
The diff coverage is 87.5000%.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #51878         +/-   ##
=================================================
- Coverage   70.6586%   54.6734%   -15.9852%     
=================================================
  Files          1477       1588        +111     
  Lines        438466     608910     +170444     
=================================================
+ Hits         309814     332912      +23098     
- Misses       109184     252851     +143667     
- Partials      19468      23147       +3679     

Flag	Coverage Δ
integration	36.6052% <70.8333%> (?)
unit	70.4527% <87.5000%> (+0.0038%)	⬆️

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	51.3332% <87.5000%> (+5.5249%)	⬆️

[D3Hunter]

@lance6716

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lance6716, wjhuang2016

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-03-19 08:24:15.625247895 +0000 UTC m=+1365082.647494282: ☑️ agreed by lance6716.
• 2024-03-19 08:41:03.432294614 +0000 UTC m=+1366090.454541001: ☑️ agreed by wjhuang2016.