fix: respect PQ num_bits for numpy codebooks#7586
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Jul 2, 2026
| validate_vector_index(dataset, "vector", refine_factor=10, pass_threshold=0.99) | ||
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| def test_index_with_pq_codebook_rejects_wrong_num_bits_shape(tmp_path): |
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praise: thanks for adding a test for the error message.
| "index_kwargs,num_centroids,pass_threshold", | ||
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| pytest.param({}, 256, 0.99, id="default_num_bits"), | ||
| pytest.param({"num_bits": 4}, 16, 0.5, id="four_bit"), |
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question: why the 50% recall threshold here? Seems rather low.
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Good point. 50% wasn't a meaningful threshold here since the codebook is random. I split out the 4-bit case to check nbits == 4 and that queries run. This also matches the Rust 4-bit PQ tests, which don't assert recall today.
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Summary
2 ** num_bitsinstead of always requiring 256 centroidspq_codebookdocstring to describe thenum_bits-dependent shapeReason
Dataset.create_index(..., index_type="IVF_PQ", num_bits=4, pq_codebook=<numpy array>)should accept a codebook with 16 centroids per sub-vector. The Python wrapper already exposesnum_bits, and the Rust PQ implementation supports 4-bit and 8-bit PQ, but the numpy validation path was still hard-coded to the 8-bit shape with 256 centroids. This rejected a valid 4-bit user-supplied codebook before it reached the Rust layer.Validation
uv run --frozen --python 3.12 pytest python/tests/test_vector_index.py::test_index_with_pq_codebook python/tests/test_vector_index.py::test_index_with_pq_codebook_rejects_wrong_num_bits_shapeuv run --frozen --python 3.12 ruff format --check --diff python/lance/dataset.py python/tests/test_vector_index.pyuv run --frozen --python 3.12 ruff check python/lance/dataset.py python/tests/test_vector_index.pygit diff --checkLocal lint note
uv run --frozen --python 3.12 make lintwas attempted. Ruff passed, but pyright failed in this local environment because optional imports such astensorflowandtorchare not installed.