forked from segmentio/parquet-go
/
compress.go
182 lines (150 loc) · 4.76 KB
/
compress.go
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package parquet
import (
"fmt"
"io"
"runtime"
"sort"
"sync"
"github.com/segmentio/parquet-go/compress"
"github.com/segmentio/parquet-go/compress/brotli"
"github.com/segmentio/parquet-go/compress/gzip"
"github.com/segmentio/parquet-go/compress/lz4"
"github.com/segmentio/parquet-go/compress/snappy"
"github.com/segmentio/parquet-go/compress/uncompressed"
"github.com/segmentio/parquet-go/compress/zstd"
"github.com/segmentio/parquet-go/format"
)
var (
// Uncompressed is a parquet compression codec representing uncompressed
// pages.
Uncompressed uncompressed.Codec
// Snappy is the SNAPPY parquet compression codec.
Snappy snappy.Codec
// Gzip is the GZIP parquet compression codec.
Gzip = gzip.Codec{
Level: gzip.DefaultCompression,
}
// Brotli is the BROTLI parquet compression codec.
Brotli = brotli.Codec{
Quality: brotli.DefaultQuality,
LGWin: brotli.DefaultLGWin,
}
// Zstd is the ZSTD parquet compression codec.
Zstd = zstd.Codec{
Level: zstd.DefaultLevel,
Concurrency: zstd.DefaultConcurrency,
}
// Lz4Raw is the LZ4_RAW parquet compression codec.
Lz4Raw = lz4.Codec{
BlockSize: lz4.DefaultBlockSize,
Level: lz4.DefaultLevel,
Concurrency: lz4.DefaultConcurrency,
}
// Table of compression codecs indexed by their code in the parquet format.
compressionCodecs = [...]compress.Codec{
format.Uncompressed: &Uncompressed,
format.Snappy: &Snappy,
format.Gzip: &Gzip,
format.Brotli: &Brotli,
format.Zstd: &Zstd,
format.Lz4Raw: &Lz4Raw,
}
// Pools of compressed page readers used to retain compression codecs across
// page reads to reduce the compute and memory footprint of creating new
// decompressors for every new page read in a parquet file.
compressedPageReaders = [len(compressionCodecs)]sync.Pool{}
)
// LookupCompressionCodec returns the compression codec associated with the
// given code.
//
// The function never returns nil. If the encoding is not supported,
// an "unsupported" codec is returned.
func LookupCompressionCodec(codec format.CompressionCodec) compress.Codec {
if codec >= 0 && int(codec) < len(compressionCodecs) {
if c := compressionCodecs[codec]; c != nil {
return c
}
}
return &unsupported{codec}
}
func acquireCompressedPageReader(codec format.CompressionCodec, page io.Reader) *compressedPageReader {
r, _ := compressedPageReaders[codec].Get().(*compressedPageReader)
if r == nil {
r = &compressedPageReader{codec: codec}
r.reader, r.err = LookupCompressionCodec(codec).NewReader(page)
runtime.SetFinalizer(r, func(r *compressedPageReader) { r.Close() })
} else {
r.Reset(page)
}
return r
}
func releaseCompressedPageReader(r *compressedPageReader) {
r.Reset(nil)
compressedPageReaders[r.codec].Put(r)
}
type compressedPageReader struct {
codec format.CompressionCodec
reader compress.Reader
err error
}
func (r *compressedPageReader) Close() error {
return r.reader.Close()
}
func (r *compressedPageReader) Read(b []byte) (int, error) {
if r.err != nil {
return 0, r.err
}
return r.reader.Read(b)
}
func (r *compressedPageReader) Reset(page io.Reader) {
r.err = r.reader.Reset(page)
}
type unsupported struct{ codec format.CompressionCodec }
func (u *unsupported) String() string {
return "UNSUPPORTED"
}
func (u *unsupported) CompressionCodec() format.CompressionCodec {
return u.codec
}
func (u *unsupported) NewReader(r io.Reader) (compress.Reader, error) {
return unsupportedReader{u}, nil
}
func (u *unsupported) NewWriter(w io.Writer) (compress.Writer, error) {
return unsupportedWriter{u}, nil
}
func (u *unsupported) error() error {
return fmt.Errorf("unsupported compression codec: %s", u.codec)
}
type unsupportedReader struct{ *unsupported }
func (r unsupportedReader) Close() error { return nil }
func (r unsupportedReader) Reset(io.Reader) error { return nil }
func (r unsupportedReader) Read(b []byte) (int, error) { return 0, r.error() }
type unsupportedWriter struct{ *unsupported }
func (w unsupportedWriter) Close() error { return nil }
func (w unsupportedWriter) Flush() error { return nil }
func (w unsupportedWriter) Reset(io.Writer) error { return nil }
func (w unsupportedWriter) Write(b []byte) (int, error) { return 0, w.error() }
func sortCodecs(codecs []compress.Codec) {
if len(codecs) > 1 {
sort.Slice(codecs, func(i, j int) bool {
return codecs[i].CompressionCodec() < codecs[j].CompressionCodec()
})
}
}
func dedupeSortedCodecs(codecs []compress.Codec) []compress.Codec {
if len(codecs) > 1 {
i := 0
for _, c := range codecs[1:] {
if c.CompressionCodec() != codecs[i].CompressionCodec() {
i++
codecs[i] = c
}
}
clear := codecs[i+1:]
for i := range clear {
clear[i] = nil
}
codecs = codecs[:i+1]
}
return codecs
}