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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/merge_operator.h"
#include "rocksdb/slice.h"
#include "utilities/merge_operators.h"
using ROCKSDB_NAMESPACE::Logger;
using ROCKSDB_NAMESPACE::MergeOperator;
using ROCKSDB_NAMESPACE::Slice;
namespace { // anonymous namespace
// Merge operator that picks the maximum operand, Comparison is based on
// Slice::compare
class MaxOperator : public MergeOperator {
public:
bool FullMergeV2(const MergeOperationInput& merge_in,
MergeOperationOutput* merge_out) const override {
Slice& max = merge_out->existing_operand;
if (merge_in.existing_value) {
max = Slice(merge_in.existing_value->data(),
merge_in.existing_value->size());
} else if (max.data() == nullptr) {
max = Slice();
}
for (const auto& op : merge_in.operand_list) {
if (max.compare(op) < 0) {
max = op;
}
}
return true;
}
bool PartialMerge(const Slice& /*key*/, const Slice& left_operand,
const Slice& right_operand, std::string* new_value,
Logger* /*logger*/) const override {
if (left_operand.compare(right_operand) >= 0) {
new_value->assign(left_operand.data(), left_operand.size());
} else {
new_value->assign(right_operand.data(), right_operand.size());
}
return true;
}
bool PartialMergeMulti(const Slice& /*key*/,
const std::deque<Slice>& operand_list,
std::string* new_value,
Logger* /*logger*/) const override {
Slice max;
for (const auto& operand : operand_list) {
if (max.compare(operand) < 0) {
max = operand;
}
}
new_value->assign(max.data(), max.size());
return true;
}
static const char* kClassName() { return "MaxOperator"; }
static const char* kNickName() { return "max"; }
const char* Name() const override { return kClassName(); }
const char* NickName() const override { return kNickName(); }
};
} // end of anonymous namespace
namespace ROCKSDB_NAMESPACE {
std::shared_ptr<MergeOperator> MergeOperators::CreateMaxOperator() {
return std::make_shared<MaxOperator>();
}
} // namespace ROCKSDB_NAMESPACE
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