prefetch: fix underlying unexpected-eof taken as EOF

[D3Hunter]

What problem does this PR solve?

Issue Number: ref #59495

Problem Summary:

What changed and how does it work?

the underlying reader might also return unexpected-eof, we need different between them, introduced in #59496

• add rangeSize to prefetch.Reader to determine where UnexpectedEOF comes from
• check error equals using goerrors.Is instead of ==. we might add stack to the error to help debug
  • Note: for the implementation of io.Reader, we still follow the API definition to return the io.EOF directly without stack, our byteReader doesn't follow the API of io.Reader, so it's ok to add stack to the error
  • And to unify code, we always use goerrors.Is to check io.EOF even for errors from io.Reader
• avoid retry when context cancel

Check List

Tests

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

same test in #50451, before it will fail with unexpected-eof, now success

• 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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[D3Hunter]

it prints too many logs when context cancel due to some goroutine in the same group failed, it's not needed, there is no further usefully info in it.

[D3Hunter]

no need to retry on context cancel

[codecov]

Codecov Report

Attention: Patch coverage is 83.58209% with 11 lines in your changes missing coverage. Please review.

Project coverage is 75.5231%. Comparing base (a5d433a) to head (4d4b432).
Report is 52 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #59752        +/-   ##
================================================
+ Coverage   72.9537%   75.5231%   +2.5693%     
================================================
  Files          1697       1746        +49     
  Lines        468912     486378     +17466     
================================================
+ Hits         342089     367328     +25239     
+ Misses       105752      96490      -9262     
- Partials      21071      22560      +1489     

Flag	Coverage Δ
integration	49.6930% <0.0000%> (?)
unit	72.7725% <83.5820%> (+0.6235%)	⬆️

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

Components	Coverage Δ
dumpling	52.6910% <ø> (ø)
parser	∅ <ø> (∅)
br	63.6838% <62.5000%> (+18.5844%)	⬆️

Copilot reviewed 19 out of 19 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (3)

pkg/util/prefetch/reader.go:71

• Converting io.ErrUnexpectedEOF to io.EOF only when readSize equals r.rangeSize assumes that the underlying reader has read the full expected range. Please verify that this invariant holds in all cases to avoid masking incomplete reads.

if errors.Is(err, io.ErrUnexpectedEOF) && readSize == r.rangeSize {

br/pkg/storage/s3.go:986

• The addition of the r.ctx.Err() == nil check prevents retries once the context is cancelled; please ensure that there are tests covering mid-read cancellation scenarios so that this behavior is fully validated.

for err != nil && errors.Cause(err) != io.EOF && r.ctx.Err() == nil && retryCnt < maxErrorRetries { //nolint:errorlint

br/pkg/storage/ks3.go:446

• Passing r.RangeSize() as the second parameter to NewReader requires that its value is valid and non-negative. It would be good to ensure that r.RangeSize() is properly validated before using it in production code.

reader = prefetch.NewReader(reader, r.RangeSize(), prefetchSize)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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• OWNERS [lance6716,tangenta]
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-02-26 12:19:33.249481848 +0000 UTC m=+444721.202640115: ☑️ agreed by lance6716.
• 2025-03-05 06:07:45.313305898 +0000 UTC m=+421778.442225635: ☑️ agreed by tangenta.