tidb key_adapter 源码
tidb key_adapter 代码
文件路径：/br/pkg/lightning/backend/local/key_adapter.go
// Copyright 2021 PingCAP, Inc.
//
// Licensed 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 local
import (
"encoding/binary"
"github.com/pingcap/errors"
"github.com/pingcap/tidb/util/codec"
)
// KeyAdapter is used to encode and decode keys.
type KeyAdapter interface {
// Encode encodes the key with its corresponding rowID. It appends the encoded key to dst and returns the
// resulting slice. The encoded key is guaranteed to be in ascending order for comparison.
Encode(dst []byte, key []byte, rowID int64) []byte
// Decode decodes the original key to dst. It appends the encoded key to dst and returns the resulting slice.
Decode(dst []byte, data []byte) ([]byte, error)
// EncodedLen returns the encoded key length.
EncodedLen(key []byte) int
}
func reallocBytes(b []byte, n int) []byte {
newSize := len(b) + n
if cap(b) < newSize {
bs := make([]byte, len(b), newSize)
copy(bs, b)
return bs
}
return b
}
type noopKeyAdapter struct{}
func (noopKeyAdapter) Encode(dst []byte, key []byte, _ int64) []byte {
return append(dst, key...)
}
func (noopKeyAdapter) Decode(dst []byte, data []byte) ([]byte, error) {
return append(dst, data...), nil
}
func (noopKeyAdapter) EncodedLen(key []byte) int {
return len(key)
}
var _ KeyAdapter = noopKeyAdapter{}
type dupDetectKeyAdapter struct{}
func (dupDetectKeyAdapter) Encode(dst []byte, key []byte, rowID int64) []byte {
dst = codec.EncodeBytes(dst, key)
dst = reallocBytes(dst, 8)
n := len(dst)
dst = dst[:n+8]
binary.BigEndian.PutUint64(dst[n:n+8], codec.EncodeIntToCmpUint(rowID))
return dst
}
func (dupDetectKeyAdapter) Decode(dst []byte, data []byte) ([]byte, error) {
if len(data) < 8 {
return nil, errors.New("insufficient bytes to decode value")
}
_, key, err := codec.DecodeBytes(data[:len(data)-8], dst[len(dst):cap(dst)])
if err != nil {
return nil, err
}
if len(dst) == 0 {
return key, nil
}
if len(dst)+len(key) <= cap(dst) {
dst = dst[:len(dst)+len(key)]
return dst, nil
}
// New slice is allocated, append key to dst manually.
return append(dst, key...), nil
}
func (dupDetectKeyAdapter) EncodedLen(key []byte) int {
return codec.EncodedBytesLength(len(key)) + 8
}
var _ KeyAdapter = dupDetectKeyAdapter{}
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