| // 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 { // 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: |
| virtual 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; |
| } |
| |
| virtual 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; |
| virtual 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; |
| } |
| |
| virtual const char* Name() const override { |
| return "PutOperator"; |
| } |
| }; |
| |
| class PutOperatorV2 : public PutOperator { |
| virtual 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; |
| } |
| |
| virtual 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 { |
| |
| std::shared_ptr<MergeOperator> MergeOperators::CreateDeprecatedPutOperator() { |
| return std::make_shared<PutOperator>(); |
| } |
| |
| std::shared_ptr<MergeOperator> MergeOperators::CreatePutOperator() { |
| return std::make_shared<PutOperatorV2>(); |
| } |
| } |