25개 이상의 토픽을 선택하실 수 없습니다.
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
81 lines
2.5 KiB
81 lines
2.5 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
//
|
|
// WriteBatch holds a collection of updates to apply atomically to a DB.
|
|
//
|
|
// The updates are applied in the order in which they are added
|
|
// to the WriteBatch. For example, the value of "key" will be "v3"
|
|
// after the following batch is written:
|
|
//
|
|
// batch.Put("key", "v1");
|
|
// batch.Delete("key");
|
|
// batch.Put("key", "v2");
|
|
// batch.Put("key", "v3");
|
|
//
|
|
// Multiple threads can invoke const methods on a WriteBatch without
|
|
// external synchronization, but if any of the threads may call a
|
|
// non-const method, all threads accessing the same WriteBatch must use
|
|
// external synchronization.
|
|
|
|
#ifndef STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
|
|
#define STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
|
|
|
|
#include <string>
|
|
#include "leveldb/export.h"
|
|
#include "leveldb/status.h"
|
|
|
|
namespace leveldb {
|
|
|
|
class Slice;
|
|
|
|
class LEVELDB_EXPORT WriteBatch {
|
|
public:
|
|
WriteBatch();
|
|
|
|
// Intentionally copyable.
|
|
WriteBatch(const WriteBatch&) = default;
|
|
WriteBatch& operator =(const WriteBatch&) = default;
|
|
|
|
~WriteBatch();
|
|
|
|
// Store the mapping "key->value" in the database.
|
|
void Put(const Slice& key, const Slice& value);
|
|
|
|
// If the database contains a mapping for "key", erase it. Else do nothing.
|
|
void Delete(const Slice& key);
|
|
|
|
// Clear all updates buffered in this batch.
|
|
void Clear();
|
|
|
|
// The size of the database changes caused by this batch.
|
|
//
|
|
// This number is tied to implementation details, and may change across
|
|
// releases. It is intended for LevelDB usage metrics.
|
|
size_t ApproximateSize() const;
|
|
|
|
// Copies the operations in "source" to this batch.
|
|
//
|
|
// This runs in O(source size) time. However, the constant factor is better
|
|
// than calling Iterate() over the source batch with a Handler that replicates
|
|
// the operations into this batch.
|
|
void Append(const WriteBatch& source);
|
|
|
|
// Support for iterating over the contents of a batch.
|
|
class Handler {
|
|
public:
|
|
virtual ~Handler();
|
|
virtual void Put(const Slice& key, const Slice& value) = 0;
|
|
virtual void Delete(const Slice& key) = 0;
|
|
};
|
|
Status Iterate(Handler* handler) const;
|
|
|
|
private:
|
|
friend class WriteBatchInternal;
|
|
|
|
std::string rep_; // See comment in write_batch.cc for the format of rep_
|
|
};
|
|
|
|
} // namespace leveldb
|
|
|
|
#endif // STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
|