pgvector for Postgres Vector Search Cheat Sheet

pgvector is an open-source PostgreSQL extension that adds vector storage and similarity search directly inside Postgres, turning an ordinary relational database into a capable vector store without any external infrastructure. It matters because it lets teams build RAG pipelines, semantic search, and recommendation engines while keeping all their data in a single ACID-compliant system they already operate. The key mental model to carry into the tables: every vector distance operator you use in a query must match the operator class chosen when the index was built — a mismatch silently falls back to a sequential scan that can be thousands of times slower.