#full-text-search

2 posts

September 15, 2026 · 8 min read

Search in Polecat, Part 1: Full text search on an index it owns

Polecat 5.29 added keyword search to the Critter Stack's SQL Server store, and it does not use SQL Server's full-text engine to do it. The inverted index Polecat maintains itself, the LINQ operators over it, and BM25 ranking derived from the token rows.

polecat sql-server dotnet critter-stack

September 15, 2026 · 6 min read

Search in Polecat, Part 3: Hybrid search and reciprocal rank fusion

Keyword search and vector search fail in different places, so a document both rank well beats either one's favourite. How Polecat 5.29 fuses the two rankings with RRF, why only the ranks are fused and never the scores, and why candidate depth has to exceed the limit.

polecat sql-server dotnet critter-stack