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