Files
lancedb/python
lancedb-gatefixer[bot] f1f34dfdd3 fix(python): instruct dimension probe for instructor embeddings (#3874)
## Summary

- pass an Instructor-compatible `[instruction, text]` pair when
detecting embedding dimensions
- add a regression test that verifies the dimension probe uses the
configured source instruction

## Root cause

`InstructorEmbeddingFunction.ndims()` encoded a bare string even though
Instructor models require instruction/text pairs. With affected
`sentence-transformers` versions, the bare input omitted
`instruction_mask` and raised `KeyError` while defining the LanceDB
schema.

## Validation

- `uv run --extra tests pytest python/tests/test_embeddings.py -q` (`14
passed, 9 skipped`)
- `uv run --project python --extra tests --extra dev ruff format --check
python/python/lancedb/embeddings/instructor.py
python/python/tests/test_embeddings.py`
- `uv run --project python --extra tests --extra dev ruff check .`

Fixes #2041

<!-- lance-gatekeeper-fix:v1 agent=4b05e0d9f3eef17bccfb446e788294f4
generation=1 -->

Co-authored-by: Gatefixer <313497061+lancedb-gatefixer[bot]@users.noreply.github.com>
2026-08-06 16:41:11 +08:00
..
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

Pre-Haswell x86_64 hosts: lancedb-compat

The default lancedb wheel targets x86-64-haswell (AVX2 + FMA + F16C) for full performance on modern hardware. Pre-Haswell hosts — Intel Sandy Bridge / Ivy Bridge / Westmere; AMD Bulldozer / Piledriver / Steamroller — don't have AVX2 and crash with Illegal instruction at import lancedb.

For those hosts, install the lancedb-compat package instead:

pip install lancedb-compat

Same Python API (import lancedb works as usual). The compat wheel is compiled at the x86-64-v2 baseline (Nehalem-class) and uses runtime SIMD dispatch in the embedded lance crate to pick the right kernel tier (scalar / AVX / AVX+FMA / AVX2+FMA / AVX-512) at load time, so it still goes fast on modern hardware while running cleanly on the pre-Haswell silicon. Use lance.simd_info() from Python to verify which tier was selected.

lancedb and lancedb-compat install to the same lancedb/ namespace and conflict at install time. Pick one. To switch, pip uninstall lancedb first, then pip install lancedb-compat (or vice-versa).

If you need a custom baseline (or lancedb-compat isn't yet published for your platform), build from source with the override:

RUSTFLAGS="-C target-cpu=x86-64-v2" maturin build --release
pip install ./target/wheels/lancedb-*.whl

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.