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session: make TxnInfo() return even if process info is empty (#57044)#57163

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session: make TxnInfo() return even if process info is empty (#57044)#57163
ti-chi-bot wants to merge 2 commits intopingcap:release-8.1from
ti-chi-bot:cherry-pick-57044-to-release-8.1

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@ti-chi-bot ti-chi-bot commented Nov 6, 2024

This is an automated cherry-pick of #57044

What problem does this PR solve?

Issue Number: close #57043

Problem Summary:

tidb/pkg/session/session.go

Lines 4026 to 4030 in c240fdf

txnInfo := tmp.TxnInfo()
if txnInfo != nil {
startTS = txnInfo.StartTS
processInfoID = txnInfo.ConnectionID
}

TxnInfo() could be nil if process info is not set(see the implementation of TxnInfo()). Such sessions are commonly used in DDL/DXF:

tidb/pkg/ddl/backfilling_operators.go

Lines 533 to 539 in c240fdf

sessCtx, err := w.sessPool.Get()
if err != nil {
logutil.Logger(w.ctx).Error("tableScanWorker get session from pool failed", zap.Error(err))
w.ctx.onError(err)
return
}
w.se = session.NewSession(sessCtx)

And they only invoke session.Begin() before using:

tidb/pkg/ddl/index_cop.go

Lines 43 to 48 in c240fdf

func wrapInBeginRollback(se *sess.Session, f func(startTS uint64) error) error {
err := se.Begin(context.Background())
if err != nil {
return errors.Trace(err)
}
defer se.Rollback()

As a result, the startTS from internal DDL sessions will not be reported to etcd, and GC safepoint will be advanced unexpectedly.

What changed and how does it work?

Make TxnInfo() return even if process info is empty.

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

@tangenta @ti-chi-bot
This is an automated cherry-pick of pingcap#57044
bbe9c7b 
Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>
@ti-chi-bot ti-chi-bot added release-note-none Denotes a PR that doesn't merit a release note. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. type/cherry-pick-for-release-8.1 This PR is cherry-picked to release-8.1 from a source PR. labels Nov 6, 2024
@ti-chi-bot ti-chi-bot mentioned this pull request Nov 6, 2024
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ti-chi-bot bot commented Nov 6, 2024

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick:

  1. It must be approved by the approvers firstly.
  2. AFTER it has been approved by approvers, please wait for the cherry-pick merging approval from triage owners.
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ti-chi-bot bot commented Nov 12, 2024

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please ask for approval from tangenta, ensuring that each of them provides their approval before proceeding. For more information see the Code Review Process.

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ti-chi-bot bot commented Nov 12, 2024 •
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@ti-chi-bot: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name Commit Details Required Rerun command
idc-jenkins-ci-tidb/check_dev f7b501d link true /test check-dev

Full PR test history. Your PR dashboard.

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codecov bot commented Nov 12, 2024 •
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Codecov Report

Attention: Patch coverage is 90.00000% with 4 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-8.1@849dcc0). Learn more about missing BASE report.

Additional details and impacted files 
@@               Coverage Diff                @@
##             release-8.1     #57163   +/-   ##
================================================
  Coverage               ?   71.1952%           
================================================
  Files                  ?       1466           
  Lines                  ?     423291           
  Branches               ?          0           
================================================
  Hits                   ?     301363           
  Misses                 ?     101422           
  Partials               ?      20506
Flag Coverage Δ
unit 71.1952% <90.0000%> (?)

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

Components Coverage Δ
dumpling 52.9656% <0.0000%> (?)
parser ∅ <0.0000%> (?)
br 41.3021% <0.0000%> (?)

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