Jack Ye
7e8f0d4982
Simplify experimental materialized views to one output-only storage
layout and one full-rebuild refresh implementation.
## Current layout
Local materialized views currently maintain incremental-refresh state
alongside the materialized values:
- an internal `__source_row_id` column for source provenance;
- `mv.definition` plus `mv.incarnation`;
- source version/timestamp, view version, and last-refresh watermarks;
- optional `mv.staging` state for table-function sources; and
- stable-row-ID requirements on the source table.
Refresh classifies source changes, appends or evicts rows when possible,
and falls back to a rebuild for unsupported deltas. Remote
create/refresh also use separate REST mutation paths.
## New layout
An MV is an ordinary Lance backing table containing only:
- the defining query's output columns;
- its current data fragments; and
- `mv.definition`, encoded as a versioned SQL envelope such as
`{"kind":"query","format":1,"query":"SELECT ..."}`.
There is no provenance column, incarnation, source/view watermark,
staging metadata, or stable-row-ID requirement. Local refresh may still
pin a source version for reproducibility, but it always recomputes the
complete result.
Full refresh streams the new result into uncommitted fragments and then
publishes a single transaction that removes every old fragment and
installs the new set. A shared conflict token prevents concurrent
replacements from both committing. This fragment-replacement primitive
is also used by Sophon's SQL worker.
## New remote create workflow
```text
Connection::create_materialized_view(...)
-> builder renders the defining SELECT
-> remote Database receives a CreateMaterializedViewRequest
-> submit CREATE MATERIALIZED VIEW ... AS ... through Flight SQL
-> retain the SQL Query handle while the Job is running
-> consume the durable SQL-job result
-> open the created table and read mv.definition
-> return MaterializedView
```
Remote refresh similarly submits `REFRESH MATERIALIZED VIEW` through
Flight SQL. Cancelling either wrapper forwards cancellation to the
retained SQL query before aborting the local task, so the server
operation is not silently left running.
## API changes
- remove incremental/no-op modes and the `full` switch;
- remove distributed grouped/partitioned refresh APIs and native
vector-source MV APIs;
- keep full-refresh results across Rust, Python, and TypeScript;
- preserve list/describe/drop as object-management operations while
routing create/refresh mutations through SQL.
The storage contract is experimental and has no compatibility shim;
views using the removed layout must be recreated.
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.