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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#include <memory>
#include "rocksdb/slice.h"
#include "rocksdb/merge_operator.h"
#include "utilities/merge_operators.h"
using namespace ROCKSDB_NAMESPACE;
namespace { // anonymous namespace
// A merge operator that mimics Put semantics
// Since this merge-operator will not be used in production,
// it is implemented as a non-associative merge operator to illustrate the
// new interface and for testing purposes. (That is, we inherit from
// the MergeOperator class rather than the AssociativeMergeOperator
// which would be simpler in this case).
//
// From the client-perspective, semantics are the same.
class PutOperator : public MergeOperator {
public:
bool FullMerge(const Slice& /*key*/, const Slice* /*existing_value*/,
const std::deque<std::string>& operand_sequence,
std::string* new_value, Logger* /*logger*/) const override {
// Put basically only looks at the current/latest value
assert(!operand_sequence.empty());
assert(new_value != nullptr);
new_value->assign(operand_sequence.back());
return true;
}
bool PartialMerge(const Slice& /*key*/, const Slice& /*left_operand*/,
const Slice& right_operand, std::string* new_value,
Logger* /*logger*/) const override {
new_value->assign(right_operand.data(), right_operand.size());
return true;
}
using MergeOperator::PartialMergeMulti;
bool PartialMergeMulti(const Slice& /*key*/,
const std::deque<Slice>& operand_list,
std::string* new_value,
Logger* /*logger*/) const override {
new_value->assign(operand_list.back().data(), operand_list.back().size());
return true;
}
const char* Name() const override { return "PutOperator"; }
};
class PutOperatorV2 : public PutOperator {
bool FullMerge(const Slice& /*key*/, const Slice* /*existing_value*/,
const std::deque<std::string>& /*operand_sequence*/,
std::string* /*new_value*/,
Logger* /*logger*/) const override {
assert(false);
return false;
}
bool FullMergeV2(const MergeOperationInput& merge_in,
MergeOperationOutput* merge_out) const override {
// Put basically only looks at the current/latest value
assert(!merge_in.operand_list.empty());
merge_out->existing_operand = merge_in.operand_list.back();
return true;
}
};
} // end of anonymous namespace
namespace ROCKSDB_NAMESPACE {
std::shared_ptr<MergeOperator> MergeOperators::CreateDeprecatedPutOperator() {
return std::make_shared<PutOperator>();
}
std::shared_ptr<MergeOperator> MergeOperators::CreatePutOperator() {
return std::make_shared<PutOperatorV2>();
}
} // namespace ROCKSDB_NAMESPACE
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