mirror of
https://github.com/lancedb/lancedb.git
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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>
104 lines
4.5 KiB
Markdown
104 lines
4.5 KiB
Markdown
# LanceDB Python SDK
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A Python library for [LanceDB](https://github.com/lancedb/lancedb).
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## Installation
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```bash
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pip install lancedb
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```
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If no wheel is published for your platform, pip builds `lancedb` from the source distribution. That build needs a [Rust toolchain](https://rustup.rs/) and [protoc](https://grpc.io/docs/protoc-installation/) (the Protocol Buffers compiler) on your `PATH`, and can take a while.
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### Pre-Haswell x86_64 hosts: `lancedb-compat`
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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`.
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For those hosts, install the `lancedb-compat` package instead:
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```bash
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pip install lancedb-compat
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```
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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.
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`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).
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If you need a custom baseline (or `lancedb-compat` isn't yet published for your platform), build from source with the override:
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```bash
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RUSTFLAGS="-C target-cpu=x86-64-v2" maturin build --release
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pip install ./target/wheels/lancedb-*.whl
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```
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### Preview Releases
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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.
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```bash
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pip install --pre --extra-index-url https://pypi.fury.io/lancedb/ lancedb
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```
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If you also need the optional `lance` Python API, install the `pylance` extra
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and include the Lance preview index:
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```bash
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pip install --pre \
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--extra-index-url https://pypi.fury.io/lancedb/ \
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--extra-index-url https://pypi.fury.io/lance-format/ \
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"lancedb[pylance]"
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```
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With uv, also select the best matching version across the indexes:
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```bash
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uv pip install --prerelease allow \
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--index https://pypi.fury.io/lancedb/ \
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--index https://pypi.fury.io/lance-format/ \
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--index-strategy unsafe-best-match \
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"lancedb[pylance]"
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```
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The LanceDB preview index contains old `pylance` releases; current Lance previews
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are published to the `lance-format` index. By default, uv only considers versions
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from the first index containing a package, which can select an old `pylance` or
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backtrack to an older LanceDB release. `unsafe-best-match` searches all configured
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indexes, like pip; use it only with indexes you trust. Install the extra rather
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than an unconstrained `pylance` so LanceDB's minimum supported version is enforced.
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### Threading in CPU-limited containers
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LanceDB uses separate pools for compute work and storage I/O. On a container with
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two visible CPUs, current releases intentionally use one compute worker by default;
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no manual configuration is needed. If every query logs an I/O core reservation
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warning on a two-CPU container, upgrade from LanceDB 0.21.1 or earlier.
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The two commonly tuned environment variables control different resources:
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- `LANCE_CPU_THREADS` overrides the number of compute workers. One worker is the
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appropriate setting for a two-CPU container when an explicit override is needed.
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- `LANCE_IO_THREADS` controls concurrent storage operations, not reserved CPU
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cores. Its default can be greater than the number of CPUs because I/O workers
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spend much of their time waiting for storage.
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Keep the defaults unless measurements show that the workload benefits from an
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override. See the [Lance threading model](https://lance.org/guide/performance/#threading-model)
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for the current defaults and tuning guidance.
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## Usage
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### Basic Example
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```python
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import lancedb
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db = lancedb.connect('<PATH_TO_LANCEDB_DATASET>')
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table = db.open_table('my_table')
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results = table.search([0.1, 0.3]).limit(20).to_list()
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print(results)
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```
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### Development
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See [CONTRIBUTING.md](./CONTRIBUTING.md) for information on how to contribute to LanceDB.
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