VectorChord Files

VectorChord 0.4 Release Notes

Major Improvements

• Streaming I/O & Page Prefetch

• Complete rewrite of page layout to enable pipelined computation with streaming I/O.

• On PostgreSQL 17, uses fadvise to prefetch buffers into the OS page cache, eliminating per-buffer read waits and fully leveraging disk throughput.
• In upcoming PostgreSQL 18, direct support for io_uring will further streamline asynchronous I/O.

• Benchmarks: 2–3× lower latency on cold queries (no buffer or page cache), translating to significantly improved tail latency in production.

• Prefilter Acceleration

• Introduces true prefilter support for vector + filter queries.

• Previous postfilter approach ranked full result sets and then applied filters—inefficient when selectivity is low (e.g., 1% filter rate).
• Applies SQL filters before full precision vector distance computations, avoiding unnecessary work.
• Benchmarks: Up to 3× faster end-to-end search on highly selective filters without any additional tuning.

Other Improvements

• Optimized Residual Quantization

• Collaboration with RaBitQ author Jianyang: refactored distance term $|⟨o, q–c⟩|$ into $⟨o, q⟩ – ⟨o, c⟩$, so the query vector is quantized only once.

• Result: \~20% QPS improvement over 0.3.

• Recommendation: Enable residual quantization for L2 workloads.

• Fast Walsh-Hadamard Transform for Rotation

• Collaboration with RaBitQ author Jianyang: replaced manual vchordrq.prewarm_dim GUC with an on-the-fly Fast Walsh-Hadamard Transform.

• Removes the need to configure a prewarmed dimension list and yields marginal speed gains during setup.

Thank you for using VectorChord! As always, we welcome feedback and contributions on GitHub.

Full Changelog: https://github.com/tensorchord/VectorChord/compare/0.3.0...0.4.0