LeonSGP
e1e87e1cae
Hugging Face `select`, `filter`, and `shuffle` can retain a physical
Arrow table while storing logical row selection/order in an indices
table. Ingesting the physical table then silently writes excluded rows
or the wrong order and can lose duplicate selections.
Read indexed datasets through bounded Arrow-format iteration, and keep
the existing direct batch path for datasets without indices. Apply the
same conversion to sync/async table creation and additions, including
DatasetDict splits. The conversion does not mutate the user's formatting
settings.
Regression coverage includes reordered/duplicate selections, filtering,
shuffling, empty selections, projected numpy/pandas/Arrow formatting,
DatasetDicts, rescanning, and bounded batches.
Validation on base d864e7198f with its
byte-identical native/config:
- Python 3.11 full CI test selection: 1564 passed, 36 skipped, 68
deselected; 162.51s pytest /171.68s wall.
- Python 3.13 full CI test selection: 1521 passed, 37 skipped, 68
deselected; 160.32s pytest /163.74s wall. Optional HF tests were skipped
in this environment.
- Python 3.13 complete doctest command: 71 passed, 6 skipped; 8.42s
pytest /12.14s wall.
- Python 3.11 HF regression module from a candidate wheel: 43 passed;
the same regression module on the unchanged baseline gives 24 failed /19
passed.
- Ruff check/format, repository pre-commit hooks, pyright with the
source import path, and `git diff --check` passed.
This is a Python-only change. Native binaries were reused from the
verified baseline; no new native build or external-service integration
tests were run. The separate schema-metadata preservation change in
#4451 addresses a different conversion defect.
The target branch currently includes newer native changes than the
verified base. Latest-main native compatibility, Linux CI, and
remote-service tests remain for CI/maintainer validation. Prepared with
AI assistance (gpt-6.1-sol).
LanceDB Python SDK
A Python library for LanceDB.
Installation
pip install lancedb
If no wheel is published for your platform, pip builds lancedb from the source distribution. That build needs a Rust toolchain and protoc (the Protocol Buffers compiler) on your PATH, and can take a while.
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
Threading in CPU-limited containers
LanceDB uses separate pools for compute work and storage I/O. On a container with two visible CPUs, current releases intentionally use one compute worker by default; no manual configuration is needed. If every query logs an I/O core reservation warning on a two-CPU container, upgrade from LanceDB 0.21.1 or earlier.
The two commonly tuned environment variables control different resources:
LANCE_CPU_THREADSoverrides the number of compute workers. One worker is the appropriate setting for a two-CPU container when an explicit override is needed.LANCE_IO_THREADScontrols concurrent storage operations, not reserved CPU cores. Its default can be greater than the number of CPUs because I/O workers spend much of their time waiting for storage.
Keep the defaults unless measurements show that the workload benefits from an override. See the Lance threading model for the current defaults and tuning guidance.
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.