Files
lancedb/python
devteamaegis 1e7326cd8c fix(rerankers/mrr): raise ValueError on empty vector_results list (#3469)
## What's broken

`MRRReranker.rerank_multivector([])` raises `IndexError: list index out
of range`. The crash happens on line 128 (the `all()` type-homogeneity
check passes vacuously on an empty iterable) and on line 134 which
accesses `vector_results[0]` unconditionally, with no prior guard for an
empty list.

## Why it happens

`all()` over an empty iterable returns `True`, so the type check
silently passes and execution falls through to `vector_results[0]` which
crashes.

## Fix

Added a two-line guard at the top of `rerank_multivector` that raises a
clear `ValueError("vector_results must not be empty")` before any
indexing occurs.

## Test

Added `test_mrr_reranker_empty_input` in `test_rerankers.py` which calls
`rerank_multivector([])` and asserts that a `ValueError` with the
message "must not be empty" is raised.

Fixes #3468

Co-authored-by: Aegis Dev <aegis@devteamaegis.com>
2026-06-03 14:05:43 -07:00
..
2025-01-29 08:27:07 -08:00
2024-04-05 16:22:59 -07:00

LanceDB Python SDK

A Python library for LanceDB.

Installation

pip install lancedb

Preview Releases

Stable releases are created about every 2 weeks. For the latest features and bug fixes, you can install the preview release. These releases receive the same level of testing as stable releases, but are not guaranteed to be available for more than 6 months after they are released. Once your application is stable, we recommend switching to stable releases.

pip install --pre --extra-index-url https://pypi.fury.io/lancedb/ lancedb

Usage

Basic Example

import lancedb
db = lancedb.connect('<PATH_TO_LANCEDB_DATASET>')
table = db.open_table('my_table')
results = table.search([0.1, 0.3]).limit(20).to_list()
print(results)

Development

See CONTRIBUTING.md for information on how to contribute to LanceDB.