KarthikSandXuanwo
702389654e
Fixes #4248. The preview index still contains pylance 1.0.0b6. uv's default first-index resolution can select it, or backtrack to an old LanceDB release when installing the extra. Meanwhile, the extra still permits pylance 5 even though current main bundles Lance 14. Raise the optional dependency to `pylance>=14.0.0b12`, the version already pinned in the test extra, and keep the lockfile metadata consistent. Document both Fury indexes and uv's `unsafe-best-match` strategy in the Python README and the source-owned quickstart (`docs/web/quickstart.mdx`). Explain the index trust requirement and recommend installing the extra to enforce the version floor. Add CI checks that reject older Lance majors and ensure the pylance and tests extras remain compatible. Run these checks when either dependency manifest changes, so a future Lance major bump cannot silently leave the Python minimum behind. ### Validation - Recreated the reported install on Ubuntu 26.04 / CPython 3.12.15 with uv 0.12.23: `lancedb==0.40.0b5` plus the old index selects `pylance==1.0.0b6`. Reproduced both the missing `blob_array` import and the unexpected `blob_handling` scanner argument using a real blob table. - Resolved the modified `python/pyproject.toml` with the pylance extra against both indexes: selects `pylance==14.0.0b18`, matching the current Rust pin. - Ran both documented pip and uv installations in isolated environments: `lancedb==0.41.0b7`, `pylance==14.0.0b18`; blob-array construction and a blob-bytes round trip through `to_pandas(blob_mode="bytes")` pass. Both package dependency checks pass. - New regression fails on the original dependency bound (27 rejected-version cases incorrectly accepted), then passes with the fix. Full CI-script suite: 3 tests pass. - `uv lock --check` with both indexes passes; focused Ruff checks pass; `git diff --check` passes. - Repository-wide Ruff reports 49 existing errors in untouched `docs/web-tests` files. Unrelated formatting changes were discarded. Runtime smoke checks used released native wheels; source dependency resolution was tested directly from the modified pyproject. No Rust or Python runtime code changes. --------- Co-authored-by: Xuanwo <github@xuanwo.io>
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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
If you also need the optional lance Python API, install the pylance extra
and include the Lance preview index:
pip install --pre \
--extra-index-url https://pypi.fury.io/lancedb/ \
--extra-index-url https://pypi.fury.io/lance-format/ \
"lancedb[pylance]"
With uv, also select the best matching version across the indexes:
uv pip install --prerelease allow \
--index https://pypi.fury.io/lancedb/ \
--index https://pypi.fury.io/lance-format/ \
--index-strategy unsafe-best-match \
"lancedb[pylance]"
The LanceDB preview index contains old pylance releases; current Lance previews
are published to the lance-format index. By default, uv only considers versions
from the first index containing a package, which can select an old pylance or
backtrack to an older LanceDB release. unsafe-best-match searches all configured
indexes, like pip; use it only with indexes you trust. Install the extra rather
than an unconstrained pylance so LanceDB's minimum supported version is enforced.
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.