parquet 49.0.0

Apache Parquet implementation in Rust
Documentation 
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# Apache Parquet Official Native Rust Implementation

[![crates.io](https://img.shields.io/crates/v/parquet.svg)](https://crates.io/crates/parquet)
[![docs.rs](https://img.shields.io/docsrs/parquet.svg)](https://docs.rs/parquet/latest/parquet/)

This crate contains the official Native Rust implementation of [Apache Parquet](https://parquet.apache.org/), which is part of the [Apache Arrow](https://arrow.apache.org/) project.

See the [API documentation](https://docs.rs/parquet/latest) for examples and the full API.

The API documentation for most recent, unreleased code is available [here](https://arrow.apache.org/rust/parquet/index.html).

## Rust Version Compatibility

This crate is tested with the latest stable version of Rust. We do not currently test against other, older versions of the Rust compiler.

## Versioning / Releases

The arrow crate follows the [SemVer standard](https://doc.rust-lang.org/cargo/reference/semver.html) defined by Cargo and works well within the Rust crate ecosystem.

However, for historical reasons, this crate uses versions with major numbers greater than `0.x` (e.g. `19.0.0`), unlike many other crates in the Rust ecosystem which spend extended time releasing versions `0.x` to signal planned ongoing API changes. Minor arrow releases contain only compatible changes, while major releases may contain breaking API changes.

## Feature Flags

The `parquet` crate provides the following features which may be enabled in your `Cargo.toml`:

- `arrow` (default) - support for reading / writing [`arrow`](https://crates.io/crates/arrow) arrays to / from parquet
- `async` - support `async` APIs for reading parquet
- `json` - support for reading / writing `json` data to / from parquet
- `brotli` (default) - support for parquet using `brotli` compression
- `flate2` (default) - support for parquet using `gzip` compression
- `lz4` (default) - support for parquet using `lz4` compression
- `zstd` (default) - support for parquet using `zstd` compression
- `snap` (default) - support for parquet using `snappy` compression
- `cli` - parquet [CLI tools](https://github.com/apache/arrow-rs/tree/master/parquet/src/bin)
- `experimental` - Experimental APIs which may change, even between minor releases

## Parquet Feature Status

- [x] All encodings supported, except for BYTE_STREAM_SPLIT ([#4102](https://github.com/apache/arrow-rs/issues/4102))
- [x] All compression codecs supported
- [x] Read support
  - [x] Primitive column value readers
  - [x] Row record reader
  - [x] Arrow record reader
  - [x] Async support (to Arrow)
- [x] Statistics support
- [x] Write support
  - [x] Primitive column value writers
  - [ ] Row record writer
  - [x] Arrow record writer
  - [x] Async support
- [x] Predicate pushdown
- [x] Parquet format 4.0.0 support

## Support for `wasm32-unknown-unknown` target

It's possible to build `parquet` for the `wasm32-unknown-unknown` target, however not all the compression features are currently unsupported due to issues with the upstream crates. In particular, the `zstd` and `lz4` features may have compilation issues. See issue [#180](https://github.com/apache/arrow-rs/issues/180).

```
cargo build -p parquet --target wasm32-unknown-unknown --no-default-features --features cli,snap,flate2,brotli
```

## License

Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0.