ALP encoding officially lands in Apache Parquet with zstd-level compression and faster decoding

mgill25 · x · 2026-09-23

Apache Parquet has officially added the ALP (Adaptive Lossless floating-Point) encoding, a lightweight scheme offering compression ratios similar to zstd with much faster decompression, random-access support, and GPU/SIMD-friendly decoding.

Best for: decimal values stored as FLOAT/DOUBLE — monetary data, geographic coordinates, and scientific measurements.

Not for: data with wide exponent ranges or many significant digits, such as vector embeddings, which should stick with PLAIN/BYTESTREAMSPLIT plus general-purpose compression.

The post explains why systems commonly store decimals as floats: Parquet's DECIMAL type requires declared precision upfront, while pandas infers float64 and NumPy has no decimal dtype at all. ALP fills this gap across the Parquet ecosystem.

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