52 lines
1.4 KiB
C++
52 lines
1.4 KiB
C++
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/**
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* Back-end implementation details specific to the Merge Operator.
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*
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* @author Deon Nicholas (dnicholas@fb.com)
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* Copyright 2013 Facebook
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*/
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#include "leveldb/merge_operator.h"
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namespace leveldb {
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// Given a "real" merge from the library, call the user's
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// associative merge function one-by-one on each of the operands.
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// NOTE: It is assumed that the client's merge-operator will handle any errors.
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bool AssociativeMergeOperator::Merge(
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const Slice& key,
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const Slice* existing_value,
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const std::deque<std::string>& operand_list,
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std::string* new_value,
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Logger* logger) const {
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// Simply loop through the operands
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Slice temp_existing;
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std::string temp_value;
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for (const auto& operand : operand_list) {
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Slice value(operand);
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if (!Merge(key, existing_value, value, &temp_value, logger)) {
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return false;
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}
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swap(temp_value, *new_value);
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temp_existing = Slice(*new_value);
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existing_value = &temp_existing;
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}
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// The result will be in *new_value. All merges succeeded.
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return true;
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}
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// Call the user defined simple merge on the operands;
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// NOTE: It is assumed that the client's merge-operator will handle any errors.
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bool AssociativeMergeOperator::PartialMerge(
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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 {
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return Merge(key, &left_operand, right_operand, new_value, logger);
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}
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} // namespace leveldb
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