variable: tidb_pipelined_dml_resource_policy

[ekexium]

What problem does this PR solve?

Issue Number: ref #50215

Problem Summary:

Provide a variable to limit the resource usage of pipelined dml, when it may use too much resource and affect other workloads.

What changed and how does it work?

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

[tiprow]

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[ekexium]

/retest

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[codecov]

Codecov Report

Attention: Patch coverage is 24.03846% with 79 lines in your changes missing coverage. Please review.

Project coverage is 73.4310%. Comparing base (5a166e1) to head (52b9dd1).
Report is 4 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #57352        +/-   ##
================================================
+ Coverage   73.0087%   73.4310%   +0.4223%     
================================================
  Files          1694       1694                
  Lines        468366     468505       +139     
================================================
+ Hits         341948     344028      +2080     
+ Misses       105384     103455      -1929     
+ Partials      21034      21022        -12     

Flag	Coverage Δ
integration	42.8036% <16.3461%> (?)
unit	72.2065% <24.0384%> (-0.0017%)	⬇️

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Components	Coverage Δ
dumpling	52.6910% <ø> (ø)
parser	∅ <ø> (∅)
br	45.2312% <ø> (+0.0339%)	⬆️

[ekexium]

@you06 @cfzjywxk @joey-yez PTAL when you have time

[cfzjywxk]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: cfzjywxk
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-02-19 01:35:56.817286898 +0000 UTC m=+1011599.213508955: ☑️ agreed by cfzjywxk.

[you06]

Suggested change

	newConfig := PipelinedDMLConfig{
	PipelinedFlushConcurrency: vardef.DefaultFlushConcurrency,
	PipelinedResolveLockConcurrency: vardef.DefaultResolveConcurrency,
	PipelinedWriteThrottleRatio: 0,
	}
	newConfig := PipelinedDMLConfig{
	PipelinedFlushConcurrency: s.PipelinedFlushConcurrency,
	PipelinedResolveLockConcurrency: s.PipelinedResolveLockConcurrency,
	PipelinedWriteThrottleRatio: s.PipelinedWriteThrottleRatio,
	}

Shall we keep the previous configuration if the user don't set it?

Unless some variables will be reset when user update another one.

set @@tidb_pipelined_dml_resource_policy = 'custom{concurrency=64}' -- PipelinedFlushConcurrency is 64
set @@tidb_pipelined_dml_resource_policy = 'custom{write_throttle_ratio=0.5}' -- PipelinedFlushConcurrency is reset to 128

[you06]

It's good to just let the omitted fields be reset to the default value. Unless the actual variable may be different from show variables like "tidb_pipelined_dml_resource_policy".

[ekexium]

some variables will be reset when user update another one

This is the intended behavior, as we're performing setting operations rather than updates, so the override behavior is appropriate.