Meilisearch: A powerful, open-source search engine offering fast and relevant full-text searches. Enhance your search capabilities with features like facet search, semantic search, hybrid search, and geosearch.

MeiliSearch is an open-source search engine that provides fast and relevant search capabilities for developers. Readers can learn about search algorithms, indexing techniques, and building search functionality into their applications. With documentation, tutorials, and community support, MeiliSearch empowers developers to enhance the search experience for their users.

Meilisearch

Meilisearch's CTO details how they patched LMDB to support nested read transactions on uncommitted writes, eliminating full database scans in their HNSW-based vector store. The previous approach used a full scan to collect memory-mapped pointers into a HashMap for multi-threaded access. Two key optimizations were made: removing unnecessary mean-degree stat computation (cutting 559s to ~2-3s), and replacing the ImmutableItems/ImmutableLinks full-scan approach with a new FrozenReader that lazily fetches graph nodes via nested read transactions distributed across rayon threads using thread-local storage. The LMDB patch required implementing an atomically reference-counted system in C11 to allow multiple concurrent nested read-only transactions from a parent write transaction. The result: inserting embeddings went from ~6/sec to ~20/sec, a 3x+ improvement, while also improving disk cache efficiency by loading only necessary pages.

Patching LMDB: how we made Meilisearch’s vector store 3× faster