PostgreSQL

Open-source relational database that doubles as a capable search platform. Native Full-Text Search (tsvector/tsquery, GIN indexes, ts_rank) plus extensions for vector search (pgvector) and BM25 (ParadeDB) let teams run Hybrid Search and RRF inside a single datastore.

• Website: https://www.postgresql.org/

Search capabilities

• Native FTS — tsvector, tsquery, websearch_to_tsquery, GIN indexes, ts_rank/ts_rank_cd. Stemming and language analyzers; phrase & boolean queries. Ranking is local term-statistics based, not BM25.
• Vector search — via pgvector (HNSW / IVFFlat).
• BM25 + faceting — via ParadeDB (pg_search) or psql_bm25s (native BM25 index access method).
• Hybrid + RRF — composable in SQL.

Strengths vs. dedicated engines

Single datastore, simpler infra, mature SQL ecosystem, strong transactional guarantees. Weaker on typo tolerance, analyzers, faceting, merchandising, search analytics, and explainability than Elasticsearch / OpenSearch.

Related

• Search using PostgreSQL — the full topic
• pgvector · ParadeDB · psql_bm25s — search extensions
• Full-Text Search · Hybrid Search · Reciprocal Rank Fusion · BM25
• Search Platforms · Elasticsearch vs OpenSearch