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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).
//
/**
* Back-end implementation details specific to the Merge Operator.
*/
#include "rocksdb/merge_operator.h"
namespace ROCKSDB_NAMESPACE {
bool MergeOperator::FullMergeV2(const MergeOperationInput& merge_in,
MergeOperationOutput* merge_out) const {
// If FullMergeV2 is not implemented, we convert the operand_list to
// std::deque<std::string> and pass it to FullMerge
std::deque<std::string> operand_list_str;
for (auto& op : merge_in.operand_list) {
operand_list_str.emplace_back(op.data(), op.size());
}
return FullMerge(merge_in.key, merge_in.existing_value, operand_list_str,
&merge_out->new_value, merge_in.logger);
}
// The default implementation of PartialMergeMulti, which invokes
// PartialMerge multiple times internally and merges two operands at
// a time.
bool MergeOperator::PartialMergeMulti(const Slice& key,
const std::deque<Slice>& operand_list,
std::string* new_value,
Logger* logger) const {
assert(operand_list.size() >= 2);
// Simply loop through the operands
Slice temp_slice(operand_list[0]);
for (size_t i = 1; i < operand_list.size(); ++i) {
auto& operand = operand_list[i];
std::string temp_value;
if (!PartialMerge(key, temp_slice, operand, &temp_value, logger)) {
return false;
}
swap(temp_value, *new_value);
temp_slice = Slice(*new_value);
}
// The result will be in *new_value. All merges succeeded.
return true;
}
// Given a "real" merge from the library, call the user's
// associative merge function one-by-one on each of the operands.
// NOTE: It is assumed that the client's merge-operator will handle any errors.
bool AssociativeMergeOperator::FullMergeV2(
const MergeOperationInput& merge_in,
MergeOperationOutput* merge_out) const {
// Simply loop through the operands
Slice temp_existing;
const Slice* existing_value = merge_in.existing_value;
for (const auto& operand : merge_in.operand_list) {
std::string temp_value;
if (!Merge(merge_in.key, existing_value, operand, &temp_value,
merge_in.logger)) {
return false;
}
swap(temp_value, merge_out->new_value);
temp_existing = Slice(merge_out->new_value);
existing_value = &temp_existing;
}
// The result will be in *new_value. All merges succeeded.
return true;
}
// Call the user defined simple merge on the operands;
// NOTE: It is assumed that the client's merge-operator will handle any errors.
bool AssociativeMergeOperator::PartialMerge(const Slice& key,
const Slice& left_operand,
const Slice& right_operand,
std::string* new_value,
Logger* logger) const {
return Merge(key, &left_operand, right_operand, new_value, logger);
}
} // namespace ROCKSDB_NAMESPACE
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