maintainer: return zero for equal event keys

[ekexium]

What problem does this PR solve?

Issue Number: close #5187

compareEventKey returned 1 when both event keys were equal, violating the comparator contract expected by callers such as slices.SortFunc.

What is changed and how it works?

Return 0 when both blockTs and isSyncPoint are equal. Add table-driven unit coverage for timestamp ordering, sync-point ordering, and both equality cases.

Check List

Tests

• Unit test

Command: make unit_test_pkg PKG=./maintainer/...

Questions

Will it cause performance regression or break compatibility?

No.

Do you need to update user documentation, design documentation or monitoring documentation?

No.

Release note

None

Summary by CodeRabbit

• Bug Fixes
  • Fixed tie-breaking logic when comparing two event keys with matching sync-point status, ensuring consistent ordering.
  • Kept behavior that equivalent event keys are treated as equal.
• Tests
  • Added table-driven unit tests covering timestamp ordering, DDL vs sync-point precedence (including reverse order), and sync-point equality cases.

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[gemini-code-assist]

Code Review

This pull request updates the compareEventKey function in maintainer/barrier_helper.go to correctly handle cases where both keys are sync points or neither is, returning 0 when they are equal instead of defaulting to 1. Additionally, a comprehensive unit test suite TestCompareEventKey has been added in maintainer/barrier_helper_test.go to verify the comparison logic. There are no review comments, and I have no additional feedback to provide.

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[Copilot]

Pull request overview

Fixes maintainer’s compareEventKey comparator to satisfy the expected ordering contract (notably for slices.SortFunc) by returning 0 when two eventKey values are equal.

Changes:

• Update compareEventKey to explicitly handle both sync-point tie-break directions and return 0 on full equality.
• Add table-driven unit tests covering timestamp ordering, sync-point ordering, and equality cases.

Validation:

• Not run here (per PR: make unit_test_pkg PKG=./maintainer/...)

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
maintainer/barrier_helper.go	Fix comparator to return 0 for equal keys and fully implement sync-point tie-break ordering.
maintainer/barrier_helper_test.go	Add unit tests validating ordering and equality behavior of compareEventKey.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 227ee7dd-6cdf-4d73-a136-eb059c7d8ac8

📥 Commits

Reviewing files that changed from the base of the PR and between 9c25760 and 83116be.

📒 Files selected for processing (2)

• maintainer/barrier_helper.go
• maintainer/barrier_helper_test.go

🚧 Files skipped from review as they are similar to previous changes (1)

• maintainer/barrier_helper.go

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📝 Walkthrough

Walkthrough

compareEventKey now returns 0 when event keys share the same timestamp and sync-point status. A table-driven unit test covers timestamp ordering, DDL versus sync-point precedence, and equality cases.

Changes

Event key comparator

Layer / File(s)	Summary
Comparator tie-breaking and coverage maintainer/barrier_helper.go, maintainer/barrier_helper_test.go	compareEventKey handles both sync-point orderings and returns 0 for equal statuses; table-driven tests validate ordering and equality behavior.

Estimated code review effort: 2 (Simple) | ~10 minutes

Poem

I’m a rabbit with keys in a row,
Sorting the carrots from high to low.
Equal little keys now rest as one,
Tests hop through each case in the sun.
No more leaps when ties are spun!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately describes the main change: returning zero for equal event keys.
Description check	✅ Passed	The description follows the template and includes the issue number, change summary, tests, answers, and release note.
Linked Issues check	✅ Passed	The implementation matches #5187 by returning 0 for equal keys and adding tests for ordering and equality cases.
Out of Scope Changes check	✅ Passed	The PR stays focused on the comparator fix and its unit tests, with no unrelated code changes.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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