zeroshade commented on a change in pull request #9817: URL: https://github.com/apache/arrow/pull/9817#discussion_r610912923
########## File path: go/parquet/compress/compress.go ########## @@ -0,0 +1,153 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +// Package compress contains the interfaces and implementations for handling compression/decompression +// of parquet data at the column levels. +package compress + +import ( + "compress/flate" + "io" + "io/ioutil" + + "github.com/apache/arrow/go/parquet/internal/gen-go/parquet" +) + +// Compression is an alias to the thrift compression codec enum type for easy use +type Compression parquet.CompressionCodec + +func (c Compression) String() string { + return parquet.CompressionCodec(c).String() +} + +// DefaultCompressionLevel will use flate.DefaultCompression since many of the compression libraries +// use that to denote "use the default". +const DefaultCompressionLevel = flate.DefaultCompression + +// Codecs is a useful struct to provide namespaced enum values to use for specifying the compression type to use +// which make for easy internal swapping between them and the thrift enum since they are initialized to the same +// constant values. +var Codecs = struct { + Uncompressed Compression + Snappy Compression + Gzip Compression + // LZO is unsupported in this library as I haven't yet found a good implementation of it for golang. + Lzo Compression + Brotli Compression + // LZ4 unsupported in this library due to problematic issues between the Hadoop LZ4 spec vs regular lz4 + // see: http://mail-archives.apache.org/mod_mbox/arrow-dev/202007.mbox/%3ccaari41v24xua8mghldvgsne+7aagohieukemw_opnhmvfmm...@mail.gmail.com%3E + Lz4 Compression + Zstd Compression +}{ + Uncompressed: Compression(parquet.CompressionCodec_UNCOMPRESSED), + Snappy: Compression(parquet.CompressionCodec_SNAPPY), + Gzip: Compression(parquet.CompressionCodec_GZIP), + Lzo: Compression(parquet.CompressionCodec_LZO), + Brotli: Compression(parquet.CompressionCodec_BROTLI), + Lz4: Compression(parquet.CompressionCodec_LZ4), + Zstd: Compression(parquet.CompressionCodec_ZSTD), +} + +// Codec is an interface which is implemented for each compression type in order to make the interactions easy to +// implement. Most consumers won't be calling GetCodec directly. +type Codec interface { + // NewReader provides a reader that wraps a stream with compressed data to stream the uncompressed data + NewReader(io.Reader) io.ReadCloser + // NewWriter provides a wrapper around a write stream to compress data before writing it. + NewWriter(io.Writer) io.WriteCloser + // NewWriterLevel is like NewWrapper but allows specifying the compression level + NewWriterLevel(io.Writer, int) (io.WriteCloser, error) + // Encode encodes a block of data given by src and returns the compressed block. dst needs to be either nil + // or sized large enough to fit the compressed block (use CompressBound to allocate). dst and src should not + // overlap since some of the compression types don't allow it. + // + // The returned slice *might* be a slice of dst if it was able to fit the whole compressed data in it. Review comment: fixed ########## File path: go/parquet/compress/zstd.go ########## @@ -0,0 +1,110 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +package compress + +import ( + "io" + "sync" + + "github.com/klauspost/compress/zstd" +) + +type zstdCodec struct{} + +type zstdcloser struct { + *zstd.Decoder +} + +var ( + enc *zstd.Encoder + dec *zstd.Decoder + initEncoder sync.Once + initDecoder sync.Once +) + +func getencoder() *zstd.Encoder { + initEncoder.Do(func() { + enc, _ = zstd.NewWriter(nil, zstd.WithZeroFrames(true)) + }) + return enc +} + +func getdecoder() *zstd.Decoder { + initDecoder.Do(func() { + dec, _ = zstd.NewReader(nil) + }) + return dec +} + +func (zstdCodec) Decode(dst, src []byte) []byte { + dst, err := getdecoder().DecodeAll(src, dst[:0]) + if err != nil { + panic(err) + } + return dst +} + +func (z *zstdcloser) Close() error { + z.Decoder.Close() + return nil +} + +func (zstdCodec) NewReader(r io.Reader) io.ReadCloser { + ret, _ := zstd.NewReader(r) + return &zstdcloser{ret} +} + +func (zstdCodec) NewWriter(w io.Writer) io.WriteCloser { + ret, _ := zstd.NewWriter(w) + return ret +} + +func (zstdCodec) NewWriterLevel(w io.Writer, level int) (io.WriteCloser, error) { + var compressLevel zstd.EncoderLevel + if level == DefaultCompressionLevel { + compressLevel = zstd.SpeedDefault + } else { + compressLevel = zstd.EncoderLevelFromZstd(level) + } + return zstd.NewWriter(w, zstd.WithEncoderLevel(compressLevel)) +} + +func (z zstdCodec) Encode(dst, src []byte) []byte { + return getencoder().EncodeAll(src, dst[:0]) +} + +func (z zstdCodec) EncodeLevel(dst, src []byte, level int) []byte { + compressLevel := zstd.EncoderLevelFromZstd(level) + if level == DefaultCompressionLevel { + compressLevel = zstd.SpeedDefault + } + enc, _ := zstd.NewWriter(nil, zstd.WithZeroFrames(true), zstd.WithEncoderLevel(compressLevel)) + return enc.EncodeAll(src, dst[:0]) +} + +// from zstd.h Review comment: added -- This is an automated message from the Apache Git Service. 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