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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"
+
+namespace { // anonymous namespace
+
+using ROCKSDB_NAMESPACE::Logger;
+using ROCKSDB_NAMESPACE::MergeOperator;
+using ROCKSDB_NAMESPACE::Slice;
+
+// 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;
+ }
+
+ static const char* kClassName() { return "PutOperator"; }
+ static const char* kNickName() { return "put_v1"; }
+ const char* Name() const override { return kClassName(); }
+ const char* NickName() const override { return kNickName(); }
+};
+
+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;
+ }
+
+ static const char* kNickName() { return "put"; }
+ const char* NickName() const override { return kNickName(); }
+};
+
+} // 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