rocksdb/table/get_context.h

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// Copyright (c) 2014, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
#pragma once
#include <string>
#include "db/merge_context.h"
#include "rocksdb/env.h"
#include "rocksdb/types.h"
namespace rocksdb {
class MergeContext;
class GetContext {
public:
enum GetState {
kNotFound,
kFound,
kDeleted,
kCorrupt,
kMerge // saver contains the current merge result (the operands)
};
GetContext(const Comparator* ucmp, const MergeOperator* merge_operator,
Logger* logger, Statistics* statistics, GetState init_state,
const Slice& user_key, std::string* ret_value, bool* value_found,
MergeContext* merge_context, Env* env,
SequenceNumber* seq = nullptr);
void MarkKeyMayExist();
// Records this key, value, and any meta-data (such as sequence number and
// state) into this GetContext.
//
// Returns True if more keys need to be read (due to merges) or
// False if the complete value has been found.
bool SaveValue(const ParsedInternalKey& parsed_key, const Slice& value);
// Simplified version of the previous function. Should only be used when we
// know that the operation is a Put.
void SaveValue(const Slice& value, SequenceNumber seq);
GetState State() const { return state_; }
// If a non-null string is passed, all the SaveValue calls will be
// logged into the string. The operations can then be replayed on
// another GetContext with replayGetContextLog.
void SetReplayLog(std::string* replay_log) { replay_log_ = replay_log; }
// Do we need to fetch the SequenceNumber for this key?
bool NeedToReadSequence() const { return (seq_ != nullptr); }
private:
const Comparator* ucmp_;
const MergeOperator* merge_operator_;
// the merge operations encountered;
Logger* logger_;
Statistics* statistics_;
GetState state_;
Slice user_key_;
std::string* value_;
bool* value_found_; // Is value set correctly? Used by KeyMayExist
MergeContext* merge_context_;
Env* env_;
// If a key is found, seq_ will be set to the SequenceNumber of most recent
// write to the key or kMaxSequenceNumber if unknown
SequenceNumber* seq_;
std::string* replay_log_;
};
void replayGetContextLog(const Slice& replay_log, const Slice& user_key,
GetContext* get_context);
} // namespace rocksdb