Benchmarks

Throughput Benchmark (QPS vs. Elasticsearch, Lucene, ParadeDB, PG GIN)

VectorChord-BM25’s Block-WeakAnd implementation with 128-document delta-bitpacked blocks and 1-byte fieldnorm quantization delivers up to 3x higher QPS than Tantivy-based PostgreSQL extensions (ParadeDB / pg_search) and an order of magnitude higher QPS than native PostgreSQL GIN indexes on Top-10 ranked queries:

Why vchord_bm25 Achieves High QPS

1. Zero Cross-Engine Serialization: Unlike foreign-data-wrapper or external Tantivy/Lucene bridges, vchord_bm25 stores its segments directly inside PostgreSQL buffer pages (PostgresRelation), avoiding tuple marshaling overhead.
2. Aggressive Block-Max Pruning: On multi-term queries, Block-WeakAnd skips over 80%–95% of 128-document posting blocks without decompressing them once the Top-10 threshold stabilizes.
3. 256-Entry Precomputed BM25 Lookup Table: Quantizing document length into a 1-byte fieldnorm replaces expensive per-document floating-point math with a single array lookup.

Retrieval Accuracy Benchmark (NDCG@10 on BEIR & LoTTE)

The table below (from our BEIR / LoTTE Hybrid Search & ColBERT Reranking evaluation) compares retrieval accuracy (NDCG@10) across:

• PostgreSQL vchord Dense Vector Search (Vector)
• PostgreSQL vchord_bm25 Lexical Search (BM25)
• Hybrid Search (vchord + vchord_bm25 with ColBERT Rerank)