58 lines
1.6 KiB
C++
58 lines
1.6 KiB
C++
/**
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* A MergeOperator for rocksdb that implements string append.
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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 "stringappend.h"
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#include <memory>
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#include <assert.h>
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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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namespace rocksdb {
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// Constructor: also specify the delimiter character.
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StringAppendOperator::StringAppendOperator(char delim_char)
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: delim_(delim_char) {
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}
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// Implementation for the merge operation (concatenates two strings)
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bool StringAppendOperator::Merge(const Slice& key,
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const Slice* existing_value,
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const Slice& value,
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std::string* new_value,
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Logger* logger) const {
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// Clear the *new_value for writing.
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assert(new_value);
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new_value->clear();
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if (!existing_value) {
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// No existing_value. Set *new_value = value
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new_value->assign(value.data(),value.size());
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} else {
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// Generic append (existing_value != null).
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// Reserve *new_value to correct size, and apply concatenation.
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new_value->reserve(existing_value->size() + 1 + value.size());
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new_value->assign(existing_value->data(),existing_value->size());
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new_value->append(1,delim_);
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new_value->append(value.data(), value.size());
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}
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return true;
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}
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const char* StringAppendOperator::Name() const {
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return "StringAppendOperator";
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}
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std::shared_ptr<MergeOperator> MergeOperators::CreateStringAppendOperator() {
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return std::make_shared<StringAppendOperator>(',');
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}
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} // namespace rocksdb
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