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101 lines
2.6 KiB
101 lines
2.6 KiB
// Copyright 2015 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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// See the License for the specific language governing permissions and
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// limitations under the License.
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package kv
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import (
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"context"
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)
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// BufferStore wraps a Retriever for read and a MemBuffer for buffered write.
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// Common usage pattern:
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//
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// bs := NewBufferStore(r) // use BufferStore to wrap a Retriever
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// // ...
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// // read/write on bs
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// // ...
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// bs.SaveTo(m) // save above operations to a Mutator
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type BufferStore struct {
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MemBuffer
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r Retriever
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}
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// NewBufferStore creates a BufferStore using r for read.
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func NewBufferStore(r Retriever) *BufferStore {
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return &BufferStore{
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r: r,
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MemBuffer: NewMemDbBuffer(),
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}
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}
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// NewBufferStoreFrom creates a BufferStore from retriever and mem-buffer.
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func NewBufferStoreFrom(r Retriever, buf MemBuffer) *BufferStore {
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return &BufferStore{
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r: r,
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MemBuffer: buf,
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}
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}
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// NewStagingBufferStore returns a BufferStore with buffer derived from the buffer.
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func NewStagingBufferStore(buf MemBuffer) *BufferStore {
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return &BufferStore{
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r: buf,
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MemBuffer: buf.NewStagingBuffer(),
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}
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}
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// Get implements the Retriever interface.
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func (s *BufferStore) Get(ctx context.Context, k Key) ([]byte, error) {
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val, err := s.MemBuffer.Get(ctx, k)
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if IsErrNotFound(err) {
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val, err = s.r.Get(ctx, k)
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}
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if err != nil {
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return nil, err
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}
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if len(val) == 0 {
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return nil, ErrNotExist
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}
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return val, nil
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}
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// Iter implements the Retriever interface.
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func (s *BufferStore) Iter(k Key, upperBound Key) (Iterator, error) {
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bufferIt, err := s.MemBuffer.Iter(k, upperBound)
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if err != nil {
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return nil, err
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}
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retrieverIt, err := s.r.Iter(k, upperBound)
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if err != nil {
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return nil, err
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}
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return NewUnionIter(bufferIt, retrieverIt, false)
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}
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// IterReverse implements the Retriever interface.
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func (s *BufferStore) IterReverse(k Key) (Iterator, error) {
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bufferIt, err := s.MemBuffer.IterReverse(k)
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if err != nil {
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return nil, err
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}
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retrieverIt, err := s.r.IterReverse(k)
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if err != nil {
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return nil, err
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}
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return NewUnionIter(bufferIt, retrieverIt, true)
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}
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// WalkBuffer iterates all buffered kv pairs.
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func (s *BufferStore) WalkBuffer(f func(k Key, v []byte) error) error {
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return WalkMemBuffer(s.MemBuffer, f)
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}
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