93 lines
2.3 KiB
Go
93 lines
2.3 KiB
Go
// Copyright 2023 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package external
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import (
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"context"
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"encoding/binary"
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"io"
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"github.com/docker/go-units"
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"github.com/pingcap/errors"
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"github.com/pingcap/tidb/br/pkg/storage"
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"github.com/pingcap/tidb/pkg/util/logutil"
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"go.uber.org/zap"
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)
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var (
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// default read buf size of kvReader, this buf is split into 3 parts, 2 for prefetch
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// from storage, 1 for read by user.
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defaultReadBufferSize = 64 * units.KiB
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)
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type kvReader struct {
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byteReader *byteReader
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}
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func newKVReader(
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ctx context.Context,
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name string,
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store storage.ExternalStorage,
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initFileOffset uint64,
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bufSize int,
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) (*kvReader, error) {
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oneThird := bufSize / 3
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sr, err := openStoreReaderAndSeek(ctx, store, name, initFileOffset, oneThird*2)
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if err != nil {
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return nil, err
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}
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br, err := newByteReader(ctx, sr, oneThird)
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if err != nil {
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return nil, err
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}
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return &kvReader{
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byteReader: br,
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}, nil
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}
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func (r *kvReader) nextKV() (key, val []byte, err error) {
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lenBytes, err := r.byteReader.readNBytes(8)
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if err != nil {
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return nil, nil, err
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}
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keyLen := int(binary.BigEndian.Uint64(lenBytes))
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lenBytes, err = r.byteReader.readNBytes(8)
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if err != nil {
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return nil, nil, noEOF(err)
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}
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valLen := int(binary.BigEndian.Uint64(lenBytes))
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keyAndValue, err := r.byteReader.readNBytes(keyLen + valLen)
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if err != nil {
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return nil, nil, noEOF(err)
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}
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return keyAndValue[:keyLen], keyAndValue[keyLen:], nil
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}
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// noEOF converts the EOF error to io.ErrUnexpectedEOF.
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func noEOF(err error) error {
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if err == io.EOF {
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logutil.BgLogger().Warn("unexpected EOF", zap.Error(errors.Trace(err)))
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return io.ErrUnexpectedEOF
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}
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return err
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}
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func (r *kvReader) Close() error {
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if p := r.byteReader.concurrentReader.largeBufferPool; p != nil {
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p.Destroy()
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}
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return r.byteReader.Close()
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}
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