94 lines
2.4 KiB
Go
94 lines
2.4 KiB
Go
|
// Copyright 2015 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,
|
||
|
|
// See the License for the specific language governing permissions and
|
||
|
|
// limitations under the License.
|
||
|
|
|
||
|
|
package kv
|
||
|
|
|
||
|
|
import (
|
||
|
|
"github.com/juju/errors"
|
||
|
|
)
|
||
|
|
|
||
|
|
// BufferStore wraps a Retriever for read and a MemBuffer for buffered write.
|
||
|
|
// Common usage pattern:
|
||
|
|
// bs := NewBufferStore(r) // use BufferStore to wrap a Retriever
|
||
|
|
// defer bs.Release() // make sure it will be released
|
||
|
|
// // ...
|
||
|
|
// // read/write on bs
|
||
|
|
// // ...
|
||
|
|
// bs.SaveTo(m) // save above operations to a Mutator
|
||
|
|
type BufferStore struct {
|
||
|
|
MemBuffer
|
||
|
|
r Retriever
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewBufferStore creates a BufferStore using r for read.
|
||
|
|
func NewBufferStore(r Retriever) *BufferStore {
|
||
|
|
return &BufferStore{
|
||
|
|
r: r,
|
||
|
|
MemBuffer: &lazyMemBuffer{},
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Get implements the Retriever interface.
|
||
|
|
func (s *BufferStore) Get(k Key) ([]byte, error) {
|
||
|
|
val, err := s.MemBuffer.Get(k)
|
||
|
|
if IsErrNotFound(err) {
|
||
|
|
val, err = s.r.Get(k)
|
||
|
|
}
|
||
|
|
if err != nil {
|
||
|
|
return nil, errors.Trace(err)
|
||
|
|
}
|
||
|
|
if len(val) == 0 {
|
||
|
|
return nil, errors.Trace(ErrNotExist)
|
||
|
|
}
|
||
|
|
return val, nil
|
||
|
|
}
|
||
|
|
|
||
|
|
// Seek implements the Retriever interface.
|
||
|
|
func (s *BufferStore) Seek(k Key) (Iterator, error) {
|
||
|
|
bufferIt, err := s.MemBuffer.Seek(k)
|
||
|
|
if err != nil {
|
||
|
|
return nil, errors.Trace(err)
|
||
|
|
}
|
||
|
|
retrieverIt, err := s.r.Seek(k)
|
||
|
|
if err != nil {
|
||
|
|
return nil, errors.Trace(err)
|
||
|
|
}
|
||
|
|
return newUnionIter(bufferIt, retrieverIt), nil
|
||
|
|
}
|
||
|
|
|
||
|
|
// WalkBuffer iterates all buffered kv pairs.
|
||
|
|
func (s *BufferStore) WalkBuffer(f func(k Key, v []byte) error) error {
|
||
|
|
iter, err := s.MemBuffer.Seek(nil)
|
||
|
|
if err != nil {
|
||
|
|
return errors.Trace(err)
|
||
|
|
}
|
||
|
|
defer iter.Close()
|
||
|
|
for ; iter.Valid(); iter.Next() {
|
||
|
|
if err := f(iter.Key(), iter.Value()); err != nil {
|
||
|
|
return errors.Trace(err)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return nil
|
||
|
|
}
|
||
|
|
|
||
|
|
// SaveTo saves all buffered kv pairs into a Mutator.
|
||
|
|
func (s *BufferStore) SaveTo(m Mutator) error {
|
||
|
|
err := s.WalkBuffer(func(k Key, v []byte) error {
|
||
|
|
if len(v) == 0 {
|
||
|
|
return errors.Trace(m.Delete(k))
|
||
|
|
}
|
||
|
|
return errors.Trace(m.Set(k, v))
|
||
|
|
})
|
||
|
|
return errors.Trace(err)
|
||
|
|
}
|