Yang Cen
0bceaaf3f0
Lance supports `search_effort`, but LanceDB cannot pass it through its query APIs. Expose the parameter in Rust, Python sync/async and TypeScript, including remote requests and hybrid query conversion, using the [Lance v14.0.0-beta.13](https://github.com/lance-format/lance/releases/tag/v14.0.0-beta.13) dependency already on main. The default is `None` (Auto, internally 0.5). Any explicit effort, including 0.5, overrides fixed `nprobes` in either setter order; explicit minimum/maximum bounds remain effective. Invalid values are rejected in the Rust core. Hybrid conversion now retains the vector probe parameters and handles an inferred FTS column without panicking. Namespace queries with explicit effort execute locally because the namespace wire model cannot carry it. MemWAL LSM queries reject it explicitly because Lance's LSM scanner does not yet expose this option. Maturin is included in the dev extra so the documented build command works in the project environment. BREAKING CHANGE: The public Rust `VectorQueryRequest` struct now includes `search_effort: Option<f64>`. Downstream code that initializes every field explicitly must add `search_effort: None` or use `..Default::default()`. Exhaustive destructuring patterns must include the new field or `..`. Query-builder calls and struct literals that already use `..Default::default()` require no source changes. The new effort setters in Python and TypeScript are additive. This PR does not change the persisted file format. Using explicit effort with remote tables requires server support for `search_effort` and its precedence over `nprobes`; the client wire tests do not establish that a deployed server supports it. Server-side support is tracked in lancedb/sophon#8607. Validation on AWS after merging current main (Lance beta.13 / SDK beta.5): - 14 Rust regressions and the API doctest pass. - 60 parameter regressions, the full 47-test namespace suite, and three API doctests pass. The parameter selection includes some namespace cases. - 40 TypeScript query tests and 54 remote tests pass; build, lint and generated docs pass. - Rust Clippy, Python package lint/format, Pyright and lockfile checks pass. Repository-wide Ruff reports 49 lint errors and 11 formatting failures in unchanged `docs/web-tests` files; those files are byte-identical to main and outside this change. All 1,103 Git-tracked files match the AWS validation checkout. No benchmark scripts or result artifacts are included, and no performance improvement is claimed. Uses lance-format/lance#9798. Server-side support is in lancedb/sophon#8607.
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
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.