Hybrid Search Techniques
Hybrid search combines keyword search and vector search.
Vector search understands meaning. Keyword search catches exact names, IDs, acronyms, and rare terms.
Why both matter
| Query type | Keyword | Vector |
|---|---|---|
| "ERR_AUTH_042" | strong | weak |
| "refund policy" | strong | strong |
| "money back after canceling" | weak | strong |
| "Q4 vendor breach process" | strong | strong |
Fusion
A hybrid system retrieves from both methods, then merges results.
Common merge approaches:
- weighted score
- reciprocal rank fusion
- reranking merged candidates
- source diversity limits
When to use hybrid search
Use it for:
- enterprise docs
- support search
- code search
- legal/policy search
- product docs with IDs and names
Evaluation
Compare:
- vector only
- keyword only
- hybrid
- hybrid plus reranking
Use real queries and expected documents.
Knowledge check
Q1: Why is vector search weak for IDs?
IDs may not have semantic meaning even though exact matching matters.
Q2: What does hybrid search merge?
Keyword and dense vector retrieval results.