234f33a3f9
Summary:
Allow `Slice` holding nullptr as a sentinel value but not in comparisons. This new restriction eliminates the need for the manual checks in 39ef900551, while still conforming to glibc's `memcmp` API. Thanks siying for the idea. Users may need to migrate, so mentioned it in HISTORY.md.
Closes https://github.com/facebook/rocksdb/pull/2777
Differential Revision: D5686016
Pulled By: ajkr
fbshipit-source-id: 03a2ca3fd9a0ebade9d0d5686c81d59a9534f563
78 lines
2.3 KiB
C++
78 lines
2.3 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#include <memory>
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#include "rocksdb/merge_operator.h"
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#include "rocksdb/slice.h"
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#include "utilities/merge_operators.h"
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using rocksdb::Slice;
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using rocksdb::Logger;
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using rocksdb::MergeOperator;
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namespace { // anonymous namespace
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// Merge operator that picks the maximum operand, Comparison is based on
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// Slice::compare
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class MaxOperator : public MergeOperator {
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public:
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virtual bool FullMergeV2(const MergeOperationInput& merge_in,
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MergeOperationOutput* merge_out) const override {
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Slice& max = merge_out->existing_operand;
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if (merge_in.existing_value) {
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max = Slice(merge_in.existing_value->data(),
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merge_in.existing_value->size());
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} else if (max.data() == nullptr) {
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max = Slice();
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}
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for (const auto& op : merge_in.operand_list) {
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if (max.compare(op) < 0) {
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max = op;
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}
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}
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return true;
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}
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virtual bool PartialMerge(const Slice& key, const Slice& left_operand,
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const Slice& right_operand, std::string* new_value,
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Logger* logger) const override {
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if (left_operand.compare(right_operand) >= 0) {
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new_value->assign(left_operand.data(), left_operand.size());
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} else {
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new_value->assign(right_operand.data(), right_operand.size());
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}
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return true;
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}
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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,
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Logger* logger) const override {
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Slice max;
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for (const auto& operand : operand_list) {
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if (max.compare(operand) < 0) {
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max = operand;
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}
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}
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new_value->assign(max.data(), max.size());
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return true;
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}
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virtual const char* Name() const override { return "MaxOperator"; }
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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::CreateMaxOperator() {
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return std::make_shared<MaxOperator>();
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}
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}
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