raw: stop scanning at the end of the keyspace

[lance6716]

Summary

For an API v2 keyspace scan, an open-ended range has an encoded upper bound at the next keyspace prefix. The final TiKV region has an empty end key, so the existing range comparison does not stop the scan. The client can then send another request starting at the empty key.

Stop after processing the final region response. This is in the shared path used by scan and scan_reverse.

Regression test

A mocked final region returns one key with a requested limit of two. The parameterized test asserts that both scan and scan_reverse return that key after exactly one request. Applied to the previous upstream code, both cases fail because they issue a second request; both pass with this fix.

Verification

• cargo fmt --all -- --check
• cargo test --lib — 104 passed
• git diff --check

The integration suite requires a running PD/TiKV cluster and was not run locally.

Summary by CodeRabbit

• Bug Fixes
  • Open-ended scans now stop when they reach the final region and no further scan key is available. This prevents an unnecessary additional scan request and ensures scanning ends correctly even when the range has no explicit end key.
  • Forward and reverse scans both return the final key-value pair when reaching the end of the scanned range.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Organization UI
• Review profile: CHILL
• Plan: Advanced
• Run ID: 364e1433-969b-47a8-9bb4-e2b9af976744

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📥 Commits

Reviewing files that changed from the base of the PR and between b0e351e and 930e46a.

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📒 Files selected for processing (1)

• src/raw/client.rs

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📝 Walkthrough

📝 Walkthrough

📝 Walkthrough

Walkthrough

scan_inner now stops when a scan response contains an empty next_key. A forward and reverse scan test checks the returned key-value pair and confirms that each scan dispatches one request.

Changes

Scan termination

Layer / File(s)	Summary
Empty next-key check src/raw/client.rs	scan_inner exits when next_key is empty. The test covers forward and reverse open-ended scans and checks that each returns the decoded key-value pair after one request.

Priority: ➖ Normal

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

Change: Bug fix

Suggested reviewers: eduralph

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Merge Risk: ⚪ Minimal · up to 9634d

Scans stop after the final region without an extra request. No merge-blocking risk is established.

Pre-merge checks | 4 | 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: stopping scans when the client reaches the end of the keyspace.

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✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Commit to this branch
• Create a new PR

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• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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[Copilot]

🟡 Changes recommended

The new termination behavior needs regression coverage for under-limit forward and reverse scans.

1 open finding

• Add regression test for empty end-key scan termination · New

What changed in this PR

Stops RawKV scans after processing the final TiKV region, preventing repeated scans at the keyspace boundary.

Changes:

• Detects an empty next-region key and terminates forward or reverse scans.

File	Description
src/​raw/​client.rs	Stops scanning when the final region is reached.

🧠 Review effort: Balanced

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ekexium, iosmanthus

The full list of commands accepted by this bot can be found here.

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Details

Needs approval from an approver in each of these files:

• OWNERS [ekexium,iosmanthus]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-10-12 02:13:18.005697767 +0000 UTC m=+610807.752928716: ☑️ agreed by ekexium.
• 2026-10-13 12:57:36.505222449 +0000 UTC m=+735866.252453338: ☑️ agreed by iosmanthus.