Refactor vector_search to bounded top-k heap

[Meru143]

Motivation

• Reduce memory growth and avoid collecting/sorting all rows in CodeIndex::vector_search by keeping only the top limit candidates while scanning embeddings.
• Make ordering deterministic for equal scores and add tests that validate behavior on large synthetic inputs.

Description

• Replace the unbounded Vec<(f64, CodeChunk)> + full sort() with a bounded min-heap (BinaryHeap<Reverse<ScoredChunk>>) maintained by a push_top_k helper to keep at most limit items while iterating rows.
• Introduce ScoredChunk with Ord/PartialOrd implemented via total_cmp and an ordinal insertion index to ensure deterministic ties.
• Add an early return for limit == 0, and finalize results by draining the heap into a Vec and sorting the small top-k list before returning.
• Add deterministic tests: vector_search_large_input_matches_full_sort_expectation (20k synthetic rows) to verify functional equivalence with a full-sort baseline and push_top_k_keeps_heap_bounded to assert bounded heap size.

Testing

• Ran cargo fmt --all successfully.
• Ran store-focused tests with cargo test -p argus-codelens store::tests:: and all store tests passed (13 passed; 0 failed), including vector_search_large_input_matches_full_sort_expectation and push_top_k_keeps_heap_bounded which both passed.
• Also ran targeted runs verifying the new helper and vector search behavior and observed no test failures.

---

Codex Task

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.

[Copilot]

Pull request overview

This PR refactors the vector_search method to use a bounded min-heap instead of collecting and sorting all search results, reducing memory usage and improving performance for large datasets. The implementation introduces a ScoredChunk struct with deterministic ordering via total_cmp and an ordinal index for tie-breaking, along with a push_top_k helper function to maintain heap bounds while scanning embeddings.

Changes:

• Introduced ScoredChunk struct with Ord/PartialOrd traits using total_cmp and ordinal-based tie-breaking for deterministic ordering
• Replaced unbounded Vec<(f64, CodeChunk)> collection with bounded BinaryHeap<Reverse<ScoredChunk>> maintained via new push_top_k helper
• Added comprehensive tests validating bounded heap behavior and functional equivalence with full-sort baseline on 20k synthetic rows

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[coderabbitai]

Warning

Rate limit exceeded

@Meru143 has exceeded the limit for the number of commits that can be reviewed per hour. Please wait 11 minutes and 36 seconds before requesting another review.

⌛ How to resolve this issue?

After the wait time has elapsed, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

We recommend that you space out your commits to avoid hitting the rate limit.

🚦 How do rate limits work?

CodeRabbit enforces hourly rate limits for each developer per organization.

Our paid plans have higher rate limits than the trial, open-source and free plans. In all cases, we re-allow further reviews after a brief timeout.

Please see our FAQ for further information.

📥 Commits

Reviewing files that changed from the base of the PR and between 1093d90 and c8d2171.

📒 Files selected for processing (1)

• crates/argus-codelens/src/store.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch codex/refactor-vector_search-to-use-bounded-heap

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}