hyparquet decompressors

!hyparquet parakeets

!coverage

This package provides decompressors for various compression codecs.
It is designed to be used with hyparquet in order to provide full support for all parquet compression formats.

Introduction

Apache Parquet is a popular columnar storage format that is widely used in data engineering, data science, and machine learning applications for efficiently storing and processing large datasets. It supports a number of different compression formats, but most parquet files use snappy compression.

Hyparquet is a fast and lightweight parquet reader that is designed to work in both node.js and the browser.

By default, hyparquet only supports uncompressed and snappy compressed files (the most common parquet compression codecs). The hyparquet-compressors package extends support for all legal parquet compression formats.

hyparquet-compressors works in both node.js and the browser. Uses js and wasm packages, no system dependencies.

Hyparquet

To use hyparquet-compressors with hyparquet, simply pass the compressors object to the parquetReadObjects function.

``js
import { parquetReadObjects } from 'hyparquet'
import { compressors } from 'hyparquet-compressors'

const data = await parquetReadObjects({ file, compressors })
`

See hyparquet repo for more info.

Compression formats

Parquet compression types supported with hyparquet-compressors:
- [X] Uncompressed
- [X] Snappy
- [x] Gzip
- [ ] LZO
- [X] Brotli
- [X] LZ4
- [X] ZSTD
- [X] LZ4_RAW

$3

Snappy compression uses hysnappy for fast snappy decompression using a minimal WASM module.

We load the wasm module _synchronously_ from base64 in the js file. This avoids a network request, and greatly simplifies bundling and serving wasm.

$3

New gzip implementation adapted from fflate.
Includes modifications to handle repeated back-to-back gzip streams that sometimes occur in parquet files (but are not supported by fflate).

For gzip, the output buffer argument is optional:
- If output is defined, the decompressor will write to output until it is full.
- If output` is undefined, the decompressor will allocate a new buffer, and expand it as needed to fit the uncompressed gzip data. Importantly, the caller should use the _returned_ buffer.

$3

Includes a minimal port of brotli.js.
Our implementation uses gzip to pre-compress the brotli dictionary, in order to minimize the bundle size.

$3

New LZ4 implementation includes support for legacy hadoop LZ4 frame format used on some old parquet files.

$3

Uses fzstd for Zstandard decompression.

Bundle size

| File | Size |
| --- | --- |
| hyparquet-compressors.min.js | 116.4kb |
| hyparquet-compressors.min.js.gz | 75.2kb |

References

- https://parquet.apache.org/docs/file-format/data-pages/compression/
- https://en.wikipedia.org/wiki/Brotli
- https://en.wikipedia.org/wiki/Gzip
- https://en.wikipedia.org/wiki/LZ4_(compression_algorithm)
- https://en.wikipedia.org/wiki/Snappy_(compression)
- https://en.wikipedia.org/wiki/Zstd
- https://github.com/101arrowz/fflate
- https://github.com/101arrowz/fzstd
- https://github.com/foliojs/brotli.js
- https://github.com/hyparam/hysnappy