// 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::Slice; using rocksdb::Logger; using rocksdb::MergeOperator; namespace { // anonymous namespace // Merge operator that picks the maximum operand, Comparison is based on // Slice::compare class MaxOperator : public MergeOperator { public: virtual 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; } virtual 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; } virtual 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; } virtual const char* Name() const override { return "MaxOperator"; } }; } // end of anonymous namespace namespace rocksdb { std::shared_ptr<MergeOperator> MergeOperators::CreateMaxOperator() { return std::make_shared<MaxOperator>(); } }