Files
lancedb/docs
Xuanwo 10f89b3c32 perf: reduce Blob read buffering and expose read window controls (#4979)
Remote Blob reads retain and concatenate intermediate IPC buffers across
batches and HTTP requests, increasing peak memory. Decode fragmented IPC
bodies using their declared length, assemble Blob values once across
batches/requests, and collect large-object Range responses into
known-size buffers. Impossible IPC/Range allocations return errors
instead of panicking. Closing a remote Blob file releases cached bytes
immediately, including while a cross-window read is waiting for the
network.

Rust and Python expose configurable Blob read buffers. Python sync/async
`fetch_blob_files` and `open_blob_file(s)` accept `buffer_size`; the
default is 512 KiB and zero disables prefetch. Explicit ranges bypass
prefetch. New PE batch-endpoint adoption is separate.

Malformed-length and retained-cache regressions fail on the previous
implementation and pass after the correction. Real HTTP tests cover
buffer propagation, close during blocked input, batch/request
aggregation, and large-object fallback. The final extension was rebuilt
before Python validation. Non-Blob Arrow arrays may still require
alignment copies; a contiguous multi-batch result still requires its
final allocation.

## Benchmark

Peak client RSS increment in KiB, using
`python/benchmarks/bench_fetch_blobs_rss.py`, independent clients and
real loopback HTTP. Both extensions were rebuilt from clean, unchanged
source with the same toolchain/configuration; loaded artifact hashes
were checked. Baseline `42f11d13a2755e44b63876b5a5edd93901291150`, after
`0a8a76de5286949d80368f95a5c529adf422c187`.

| Equivalent fetch workload | Payload | Before | After |
| --- | ---: | ---: | ---: |
| Single response, one batch | 48 MiB | 63,812 | 63,896 |
| Multiple responses, one batch per response | 144 MiB | 423,104 |
195,628 |
| Single response, 12 rows per batch | 48 MiB | 130,520 | 71,348 |
| Multiple responses, 12 rows per batch | 144 MiB | 363,144 | 172,748 |
| One oversized row, Range fallback | 70 MiB | 182,816 | 85,548 |

These are one observation per workload and build, not a statistical
distribution or memory upper bound. The single-batch workload shows no
improvement. Cloud/Sophon deployment, credentialed S3 and long-running
stress have not been exercised.
2026-11-13 02:05:09 +08:00
..

LanceDB Documentation

For website guides in docs/web, start with Documentation in CONTRIBUTING.md. That covers editing pages, generated examples, previews, availability and drafts.

This page covers the SDK reference in docs/src, built with MkDocs. Its GitHub Actions workflow builds and deploys on pushes to main, so it can include unreleased APIs. That is separate from the release editions of the Mintlify website.

Building the docs

Setup

  1. Install LanceDB Python. See setup in Python contributing guide. Run make develop to install the Python package.
  2. Install documentation dependencies. From LanceDB repo root: pip install -r docs/requirements.txt

Preview the docs

Run these commands from the LanceDB repository root. The subshell changes into docs to load mkdocs.yml, while leaving your shell in the repository root.

(cd docs && PYTHONPATH=. mkdocs serve)

If you want to just generate the HTML files:

(cd docs && PYTHONPATH=. mkdocs build)

If successful, you should see a docs/site directory in the repository root that you can verify locally.

Adding examples

To make sure examples are correct, we put examples in test files so they can be run as part of our test suites.

You can see the tests are at:

  • Python: python/python/tests/docs
  • Typescript: nodejs/examples/

Checking python examples

cd python
pytest -vv python/tests/docs

Checking typescript examples

The examples depend on @lancedb/lancedb at file:../dist, so the package must be built before running the tests. This uses pnpm; see the Typescript contributing guide for the toolchain setup.

pushd nodejs
pnpm install
pnpm build
popd

Then you can run the examples by going to the nodejs/examples directory, which is a separate pnpm package with its own lockfile:

pushd nodejs/examples
pnpm install
pnpm test
popd

API documentation

Python

The Python API documentation is organized based on the file docs/src/python/python.md. We manually add entries there so we can control the organization of the reference page. However, this means any new types must be manually added to the file. No additional steps are needed to generate the API documentation.

Typescript

The typescript API documentation is generated from the typescript source code using typedoc.

When new APIs are added, you must manually re-run the typedoc command to update the API documentation. The new files should be checked into the repository.

pushd nodejs
# `pnpm docs` would invoke pnpm's built-in `docs` command, not the script.
pnpm run docs
popd