txnkv: fix SetCommitWaitUntilTSOTimeout does not work in causal consistency

[lcwangchao]

fix #1846

Summary by CodeRabbit

Release Notes

• Tests

  • Expanded test coverage for async commit functionality and causal consistency validation in transaction processing scenarios.

• Bug Fixes

  • Improved commit timestamp calculation to correctly handle deferred wait-until-timestamp requirements, particularly when combined with async commit and causal consistency features.

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[coderabbitai]

📝 Walkthrough

Walkthrough

This PR fixes a bug where SetCommitWaitUntilTSO didn't work when causal consistency was enabled. The fix modifies the timestamp fetch condition in the two-phase commit flow to also trigger when commitWaitUntilTSO is configured, independent of linearizability requirements. Test coverage is expanded to verify the fix.

Changes

Cohort / File(s)	Summary
Test case expansion integration_tests/option_test.go	Removed early skip guard; introduced extraPrepare test parameter to enable configurable transaction options. Added two test cases for async commit with 1PC and causal consistency scenarios.
Core commit logic txnkv/transaction/2pc.go	Modified condition for fetching commit timestamp from TSO: now triggers when commitTSMayBeCalculated && (needLinearizability() || txn.commitWaitUntilTSO > 0) instead of only checking needLinearizability.
Dependency update go.mod	Minor manifest version adjustments.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 A carrot grows when timestamps align,
No more causal confusion, the logic's so fine,
With two-phase commits now working their grace,
TSO waits without leaving a trace,
Consistency blooms in this protocol's embrace! 🥕

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the core fix: enabling SetCommitWaitUntilTSOTimeout to work when causal consistency is enabled, which directly addresses the problem identified in the changeset.
Linked Issues check	✅ Passed	The code changes successfully address issue #1846 by modifying the condition to fetch commit timestamps even when causal consistency is enabled, allowing SetCommitWaitUntilTSO to work as intended.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing SetCommitWaitUntilTSO behavior with causal consistency; the test additions and conditional logic modifications are scoped to addressing the linked issue.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, ekexium, tiancaiamao

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Needs approval from an approver in each of these files:

• OWNERS [cfzjywxk,ekexium]
• txnkv/OWNERS [cfzjywxk,ekexium]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-01-21 06:15:30.664514004 +0000 UTC m=+560958.278470860: ☑️ agreed by cfzjywxk.
• 2026-01-21 07:05:55.207030015 +0000 UTC m=+563982.820986871: ☑️ agreed by ekexium.