FTS5

FTS5 is a high-performance SQLite virtual table module designed for lightning-fast full-text indexing and prefix searching.

FTS5 replaces its predecessors (FTS3 and FTS4) with a revamped ranking system using the BM25 algorithm and a more efficient data structure. It handles complex queries across millions of rows with sub-millisecond latency: supporting proximity searches, boolean operators, and custom tokenizers. Developers use it to build robust search features directly within the database layer, eliminating the need for external search engines like Elasticsearch for many applications.

https://www.sqlite.org/fts5.html