Linear Combination Reranker

Learn about LanceDB’s deprecated Linear Combination Reranker for combining semantic and full-text search scores.

Linear Combination Reranker

Note: This reranker is deprecated. Use the RRFReranker if you need a score-based reranker.

The Linear Combination Reranker combines the results of semantic and full-text search using a linear combination of the scores. The weights for the linear combination can be specified, and defaults to 0.7, i.e, 70% weight for semantic search and 30% weight for full-text search.

Note: Supported query type – Hybrid search only.

Accepted Arguments

Argument	Type	Default	Description
weight	float	0.7	The weight to use for the semantic search score. The weight for the full-text search score is 1 - weight.
fill	float	1.0	Score used when a result is missing from one side of the hybrid query. The default strongly penalizes missing vector or FTS matches.
return_score	str	"relevance"	Options are “relevance” or “all”. The type of score to return. If “relevance”, returns only _relevance_score. If “all”, returns all scores from the vector and FTS search along with the relevance score.

weight must be between 0 and 1. If either the vector or FTS side returns no rows, the reranker returns the non-empty side with _relevance_score attached rather than failing.

Supported Scores for each query type

You can specify the type of scores you want the reranker to return. The following are the supported scores for each query type:

Hybrid Search

return_score	Status	Description
relevance	✅ Supported	Results only have the _relevance_score column
all	✅ Supported	Results have vector(_distance) and FTS(score) along with Hybrid Search score(_distance)