Full-text search

A full-text index splits text into words, normalises them (lower case, word stems) and records where each word appears, so a search for 'running shoes' finds 'shoes for runners' quickly and ranks it with a formula such as BM25. A plain LIKE query cannot rank results and gets slow on big tables.

Many databases have it built in: SQLite's FTS5 extension, PostgreSQL's tsvector columns, MongoDB Atlas Search. Dedicated engines such as Elasticsearch, OpenSearch, Meilisearch and Typesense add typo tolerance and filters. Combining it with vector search gives hybrid search.