`RRFReranker.rerank_hybrid` and `MRRReranker.rerank_hybrid` merge the
vector and FTS results with the base `merge_results`, which keeps only
the first copy of a duplicated row. With `return_score="all"`, a row
that both searches found therefore comes back with `_score = None`, even
though the FTS search scored it. `LinearCombinationReranker` already
copies the FTS score onto such rows.
Reproduction against `lancedb` 0.40.0:
```python
import pyarrow as pa
from lancedb.rerankers import RRFReranker
vector = pa.table({"_rowid": pa.array([1, 2], pa.uint64()), "text": ["a", "b"],
"_distance": pa.array([0.1, 0.2], pa.float32())})
fts = pa.table({"_rowid": pa.array([2, 3], pa.uint64()), "text": ["b", "c"],
"_score": pa.array([5.0, 4.0], pa.float32())})
RRFReranker(return_score="all").rerank_hybrid("q", vector, fts).to_pylist()
# row 2: _distance=0.2, _score=None (expected _score=5.0)
```
`table.search(query_type="hybrid")` is not affected, because
`_combine_hybrid_results` restores the original `_distance` and `_score`
by `_rowid` after reranking. The wrong value shows up when
`rerank_hybrid` is called directly, for example from a custom reranker
that wraps RRF or MRR.
The fix uses `_merge_and_keep_scores` when `return_score="all"`, the
same pattern the model-based rerankers (`CohereReranker`,
`CrossEncoderReranker`, `JinaReranker`, `OpenaiReranker`,
`VoyageAIReranker`, ...) already use. The relevance-only path is
unchanged.
Tests: added `test_rank_fusion_return_score_all_keeps_both_scores` for
both rerankers. It fails without the fix and passes with it. I ran it
against the released 0.40.0 package with this branch's
`rerankers/{base,rrf,mrr}.py` dropped in; `rrf.py` and `mrr.py` on
`main` are identical to 0.40.0. The other reranker tests give the same
results with and without the change. `ruff format` and `ruff check` are
clean.
I used an AI assistant (Claude) while working on this; I reviewed and
tested the change.
Co-authored-by: Xuanwo <github@xuanwo.io>
The Multimodal Lakehouse for AI
How to Install ✦ Detailed Documentation ✦ Tutorials and Recipes ✦ Contributors
The ultimate multimodal data platform for AI/ML applications.
LanceDB is designed for fast, scalable, and production-ready vector search. It is built on top of the Lance columnar format. You can store, index, and search over petabytes of multimodal data and vectors with ease. LanceDB is a central location where developers can build, train and analyze their AI workloads.
Demo: Multimodal Search by Keyword, Vector or with SQL
Star LanceDB to get updates!
Key Features:
- Fast Vector Search: Search billions of vectors in milliseconds with state-of-the-art indexing.
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- Multimodal Support: Store, query and filter vectors, metadata and multimodal data (text, images, videos, point clouds, and more).
- Advanced Features: Zero-copy, automatic versioning, manage versions of your data without needing extra infrastructure. GPU support in building vector index.
Products:
- Open Source & Local: 100% open source, runs locally or in your cloud. No vendor lock-in.
- Cloud and Enterprise: Production-scale vector search with no servers to manage. Complete data sovereignty and security.
Ecosystem:
- Columnar Storage: Built on the Lance columnar format for efficient storage and analytics.
- Seamless Integration: Python, Node.js, Rust, and REST APIs for easy integration. Native Python and Javascript/Typescript support.
- Rich Ecosystem: Integrations with LangChain 🦜️🔗, LlamaIndex 🦙, Apache-Arrow, Pandas, Polars, DuckDB and more on the way.
How to Install:
Follow the Quickstart doc to set up LanceDB locally.
API & SDK: We also support Python, Typescript and Rust SDKs
| Interface | Documentation |
|---|---|
| Python SDK | https://lancedb.github.io/lancedb/python/python/ |
| Typescript SDK | https://lancedb.github.io/lancedb/js/globals/ |
| Rust SDK | https://docs.rs/lancedb/latest/lancedb/index.html |
| REST API | https://docs.lancedb.com/api-reference/rest |
Join Us and Contribute
We welcome contributions from everyone! Whether you're a developer, researcher, or just someone who wants to help out.
If you have any suggestions or feature requests, please feel free to open an issue on GitHub or discuss it on our Discord server.
Check out the GitHub Issues if you would like to work on the features that are planned for the future. If you have any suggestions or feature requests, please feel free to open an issue on GitHub.

