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file_reader.go
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file_reader.go
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// 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 file
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"os"
"runtime"
"sync"
"github.com/apache/arrow/go/v17/arrow/memory"
"github.com/apache/arrow/go/v17/parquet"
"github.com/apache/arrow/go/v17/parquet/internal/encryption"
"github.com/apache/arrow/go/v17/parquet/metadata"
"golang.org/x/xerrors"
)
const (
footerSize uint32 = 8
)
var (
magicBytes = []byte("PAR1")
magicEBytes = []byte("PARE")
errInconsistentFileMetadata = xerrors.New("parquet: file is smaller than indicated metadata size")
)
// Reader is the main interface for reading a parquet file
type Reader struct {
r parquet.ReaderAtSeeker
props *parquet.ReaderProperties
metadata *metadata.FileMetaData
footerOffset int64
fileDecryptor encryption.FileDecryptor
bufferPool sync.Pool
}
type ReadOption func(*Reader)
// WithReadProps specifies a specific reader properties instance to use, rather
// than using the default ReaderProperties.
func WithReadProps(props *parquet.ReaderProperties) ReadOption {
return func(r *Reader) {
r.props = props
}
}
// WithMetadata allows providing a specific FileMetaData object rather than reading
// the file metadata from the file itself.
func WithMetadata(m *metadata.FileMetaData) ReadOption {
return func(r *Reader) {
r.metadata = m
}
}
// OpenParquetFile will return a Reader for the given parquet file on the local file system.
//
// Optionally the file can be memory mapped for faster reading. If no read properties are provided
// then the default ReaderProperties will be used. The WithMetadata option can be used to provide
// a FileMetaData object rather than reading the file metadata from the file.
func OpenParquetFile(filename string, memoryMap bool, opts ...ReadOption) (*Reader, error) {
var source parquet.ReaderAtSeeker
var err error
if memoryMap {
source, err = mmapOpen(filename)
if err != nil {
return nil, err
}
} else {
source, err = os.Open(filename)
if err != nil {
return nil, err
}
}
return NewParquetReader(source, opts...)
}
// NewParquetReader returns a FileReader instance that reads a parquet file which can be read from r.
// This reader needs to support Read, ReadAt and Seeking.
//
// If no read properties are provided then the default ReaderProperties will be used. The WithMetadata
// option can be used to provide a FileMetaData object rather than reading the file metadata from the file.
func NewParquetReader(r parquet.ReaderAtSeeker, opts ...ReadOption) (*Reader, error) {
var err error
f := &Reader{r: r}
for _, o := range opts {
o(f)
}
if f.footerOffset <= 0 {
f.footerOffset, err = r.Seek(0, io.SeekEnd)
if err != nil {
return nil, fmt.Errorf("parquet: could not retrieve footer offset: %w", err)
}
}
if f.props == nil {
f.props = parquet.NewReaderProperties(memory.NewGoAllocator())
}
f.bufferPool = sync.Pool{
New: func() interface{} {
buf := memory.NewResizableBuffer(f.props.Allocator())
runtime.SetFinalizer(buf, func(obj *memory.Buffer) {
obj.Release()
})
return buf
},
}
if f.metadata == nil {
return f, f.parseMetaData()
}
return f, nil
}
// BufferPool returns the internal buffer pool being utilized by this reader.
// This is primarily for use by the pqarrow.FileReader or anything that builds
// on top of the Reader and constructs their own ColumnReaders (like the
// RecordReader)
func (f *Reader) BufferPool() *sync.Pool {
return &f.bufferPool
}
// Close will close the current reader, and if the underlying reader being used
// is an `io.Closer` then Close will be called on it too.
func (f *Reader) Close() error {
if r, ok := f.r.(io.Closer); ok {
return r.Close()
}
return nil
}
// MetaData returns the underlying FileMetadata object
func (f *Reader) MetaData() *metadata.FileMetaData { return f.metadata }
// parseMetaData handles parsing the metadata from the opened file.
func (f *Reader) parseMetaData() error {
if f.footerOffset <= int64(footerSize) {
return fmt.Errorf("parquet: file too small (size=%d)", f.footerOffset)
}
buf := make([]byte, footerSize)
// backup 8 bytes to read the footer size (first four bytes) and the magic bytes (last 4 bytes)
n, err := f.r.ReadAt(buf, f.footerOffset-int64(footerSize))
if err != nil && err != io.EOF {
return fmt.Errorf("parquet: could not read footer: %w", err)
}
if n != len(buf) {
return fmt.Errorf("parquet: could not read %d bytes from end of file", len(buf))
}
size := int64(binary.LittleEndian.Uint32(buf[:4]))
if size < 0 || size+int64(footerSize) > f.footerOffset {
return errInconsistentFileMetadata
}
fileDecryptProps := f.props.FileDecryptProps
switch {
case bytes.Equal(buf[4:], magicBytes): // non-encrypted metadata
buf = make([]byte, size)
if _, err := f.r.ReadAt(buf, f.footerOffset-int64(footerSize)-size); err != nil {
return fmt.Errorf("parquet: could not read footer: %w", err)
}
f.metadata, err = metadata.NewFileMetaData(buf, nil)
if err != nil {
return fmt.Errorf("parquet: could not read footer: %w", err)
}
if !f.metadata.IsSetEncryptionAlgorithm() {
if fileDecryptProps != nil && !fileDecryptProps.PlaintextFilesAllowed() {
return fmt.Errorf("parquet: applying decryption properties on plaintext file")
}
} else {
if err := f.parseMetaDataEncryptedFilePlaintextFooter(fileDecryptProps, buf); err != nil {
return err
}
}
case bytes.Equal(buf[4:], magicEBytes): // encrypted metadata
buf = make([]byte, size)
if _, err := f.r.ReadAt(buf, f.footerOffset-int64(footerSize)-size); err != nil {
return fmt.Errorf("parquet: could not read footer: %w", err)
}
if fileDecryptProps == nil {
return xerrors.New("could not read encrypted metadata, no decryption found in reader's properties")
}
fileCryptoMetadata, err := metadata.NewFileCryptoMetaData(buf)
if err != nil {
return err
}
algo := fileCryptoMetadata.EncryptionAlgorithm()
fileAad, err := f.handleAadPrefix(fileDecryptProps, &algo)
if err != nil {
return err
}
f.fileDecryptor = encryption.NewFileDecryptor(fileDecryptProps, fileAad, algo.Algo, string(fileCryptoMetadata.KeyMetadata()), f.props.Allocator())
f.metadata, err = metadata.NewFileMetaData(buf[fileCryptoMetadata.Len():], f.fileDecryptor)
if err != nil {
return fmt.Errorf("parquet: could not read footer: %w", err)
}
default:
return fmt.Errorf("parquet: magic bytes not found in footer. Either the file is corrupted or this isn't a parquet file")
}
return nil
}
func (f *Reader) handleAadPrefix(fileDecrypt *parquet.FileDecryptionProperties, algo *parquet.Algorithm) (string, error) {
aadPrefixInProps := fileDecrypt.AadPrefix()
aadPrefix := []byte(aadPrefixInProps)
fileHasAadPrefix := algo.Aad.AadPrefix != nil && len(algo.Aad.AadPrefix) > 0
aadPrefixInFile := algo.Aad.AadPrefix
if algo.Aad.SupplyAadPrefix && aadPrefixInProps == "" {
return "", xerrors.New("AAD Prefix used for file encryption but not stored in file and not supplied in decryption props")
}
if fileHasAadPrefix {
if aadPrefixInProps != "" {
if aadPrefixInProps != string(aadPrefixInFile) {
return "", xerrors.New("AAD prefix in file and in properties but not the same")
}
}
aadPrefix = aadPrefixInFile
if fileDecrypt.Verifier != nil {
fileDecrypt.Verifier.Verify(string(aadPrefix))
}
} else {
if !algo.Aad.SupplyAadPrefix && aadPrefixInProps != "" {
return "", xerrors.New("AAD Prefix set in decryptionproperties but was not used for file encryption")
}
if fileDecrypt.Verifier != nil {
return "", xerrors.New("AAD Prefix Verifier is set but AAD Prefix not found in file")
}
}
return string(append(aadPrefix, algo.Aad.AadFileUnique...)), nil
}
func (f *Reader) parseMetaDataEncryptedFilePlaintextFooter(decryptProps *parquet.FileDecryptionProperties, data []byte) error {
if decryptProps != nil {
algo := f.metadata.EncryptionAlgorithm()
fileAad, err := f.handleAadPrefix(decryptProps, &algo)
if err != nil {
return err
}
f.fileDecryptor = encryption.NewFileDecryptor(decryptProps, fileAad, algo.Algo, string(f.metadata.GetFooterSigningKeyMetadata()), f.props.Allocator())
// set the InternalFileDecryptor in the metadata as well, as it's used
// for signature verification and for ColumnChunkMetaData creation.
f.metadata.FileDecryptor = f.fileDecryptor
if decryptProps.PlaintextFooterIntegrity() {
if len(data)-f.metadata.Size() != encryption.GcmTagLength+encryption.NonceLength {
return xerrors.New("failed reading metadata for encryption signature")
}
if !f.metadata.VerifySignature(data[f.metadata.Size():]) {
return xerrors.New("parquet crypto signature verification failed")
}
}
}
return nil
}
// WriterVersion returns the Application Version that was written in the file
// metadata
func (f *Reader) WriterVersion() *metadata.AppVersion {
return f.metadata.WriterVersion()
}
// NumRows returns the total number of rows in this parquet file.
func (f *Reader) NumRows() int64 {
return f.metadata.GetNumRows()
}
// NumRowGroups returns the total number of row groups in this file.
func (f *Reader) NumRowGroups() int {
return len(f.metadata.GetRowGroups())
}
// RowGroup returns a reader for the desired (0-based) row group
func (f *Reader) RowGroup(i int) *RowGroupReader {
rg := f.metadata.RowGroups[i]
return &RowGroupReader{
fileMetadata: f.metadata,
rgMetadata: metadata.NewRowGroupMetaData(rg, f.metadata.Schema, f.WriterVersion(), f.fileDecryptor),
props: f.props,
r: f.r,
sourceSz: f.footerOffset,
fileDecryptor: f.fileDecryptor,
bufferPool: &f.bufferPool,
}
}