- Understand when purely vector search fails.
- Combine dense search, sparse search, and filters.
- Use reranking to improve the final chunks.
Recommended pipeline
query -> optional rewriting -> permission filters -> dense retrieval -> sparse retrieval -> result fusion -> reranking -> top chunks with citations -> generation
Signals for hybrid search
- Users ask about codes, IDs, or exact clauses.
- There is a lot of internal terminology.
- Documents mix tables, text, and references.
- Semantic search returns "almost correct" answers.