119 lines
3.6 KiB
Go
119 lines
3.6 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 common
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import (
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"github.com/pingcap/errors"
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"github.com/pingcap/tidb/pkg/util/codec"
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)
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// KeyAdapter is used to encode and decode keys so that duplicate key can be
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// identified by rowID and avoid overwritten.
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type KeyAdapter interface {
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// Encode encodes the key with its corresponding rowID. It appends the encoded
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// key to dst and returns the resulting slice. The encoded key is guaranteed to
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// be in ascending order for comparison.
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// rowID must be a coded mem-comparable value, one way to get it is to use
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// tidb/util/codec package.
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Encode(dst []byte, key []byte, rowID []byte) []byte
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// Decode decodes the original key to dst. It appends the encoded key to dst and returns the resulting slice.
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Decode(dst []byte, data []byte) ([]byte, error)
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// EncodedLen returns the encoded key length.
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EncodedLen(key []byte, rowID []byte) int
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}
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func reallocBytes(b []byte, n int) []byte {
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newSize := len(b) + n
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if cap(b) < newSize {
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bs := make([]byte, len(b), newSize)
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copy(bs, b)
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return bs
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}
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return b
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}
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// NoopKeyAdapter is a key adapter that does nothing.
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type NoopKeyAdapter struct{}
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// Encode implements KeyAdapter.
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func (NoopKeyAdapter) Encode(dst []byte, key []byte, _ []byte) []byte {
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return append(dst, key...)
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}
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// Decode implements KeyAdapter.
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func (NoopKeyAdapter) Decode(dst []byte, data []byte) ([]byte, error) {
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return append(dst, data...), nil
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}
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// EncodedLen implements KeyAdapter.
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func (NoopKeyAdapter) EncodedLen(key []byte, _ []byte) int {
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return len(key)
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}
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var _ KeyAdapter = NoopKeyAdapter{}
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// DupDetectKeyAdapter is a key adapter that appends rowID to the key to avoid
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// overwritten.
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type DupDetectKeyAdapter struct{}
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// Encode implements KeyAdapter.
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func (DupDetectKeyAdapter) Encode(dst []byte, key []byte, rowID []byte) []byte {
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dst = codec.EncodeBytes(dst, key)
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dst = reallocBytes(dst, len(rowID)+2)
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dst = append(dst, rowID...)
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rowIDLen := uint16(len(rowID))
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dst = append(dst, byte(rowIDLen>>8), byte(rowIDLen))
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return dst
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}
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// Decode implements KeyAdapter.
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func (DupDetectKeyAdapter) Decode(dst []byte, data []byte) ([]byte, error) {
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if len(data) < 2 {
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return nil, errors.New("insufficient bytes to decode value")
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}
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rowIDLen := uint16(data[len(data)-2])<<8 | uint16(data[len(data)-1])
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tailLen := int(rowIDLen + 2)
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if len(data) < tailLen {
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return nil, errors.New("insufficient bytes to decode value")
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}
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_, key, err := codec.DecodeBytes(data[:len(data)-tailLen], dst[len(dst):cap(dst)])
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if err != nil {
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return nil, err
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}
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if len(dst) == 0 {
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return key, nil
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}
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if len(dst)+len(key) <= cap(dst) {
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dst = dst[:len(dst)+len(key)]
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return dst, nil
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}
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// New slice is allocated, append key to dst manually.
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return append(dst, key...), nil
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}
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// EncodedLen implements KeyAdapter.
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func (DupDetectKeyAdapter) EncodedLen(key []byte, rowID []byte) int {
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return codec.EncodedBytesLength(len(key)) + len(rowID) + 2
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}
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var _ KeyAdapter = DupDetectKeyAdapter{}
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var (
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// MinRowID is the minimum rowID value after DupDetectKeyAdapter.Encode().
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MinRowID = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0}
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)
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