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/**
* Copyright (C) 2019-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/db/pipeline/document.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/query/sort_pattern.h"
#include "mongo/db/sorter/sorter.h"
namespace mongo {
/**
* The SortExecutor class is the internal implementation of sorting for query execution. The
* caller should provide input documents by repeated calls to the add() function, and then
* complete the loading process with a single call to loadingDone(). Finally, getNext() should be
* called to return the documents one by one in sorted order.
*/
class SortExecutor {
public:
/**
* If the passed in limit is 0, this is treated as no limit.
*/
SortExecutor(SortPattern sortPattern,
uint64_t limit,
uint64_t maxMemoryUsageBytes,
std::string tempDir,
bool allowDiskUse);
boost::optional<Document> getNext();
const SortPattern& sortPattern() const {
return _sortPattern;
}
/**
* Absorbs 'limit', enabling a top-k sort. It is safe to call this multiple times, it will keep
* the smallest limit.
*/
void setLimit(uint64_t limit) {
if (!_limit || limit < _limit)
_limit = limit;
}
uint64_t getLimit() const {
return _limit;
}
bool hasLimit() const {
return _limit > 0;
}
bool wasDiskUsed() const {
return _wasDiskUsed;
}
/**
* Signals to the sort executor that there will be no more input documents.
*/
void loadingDone();
/**
* Add a Document with sort key specified by Value to the DocumentSorter.
*/
void add(Value, Document);
private:
using DocumentSorter = Sorter<Value, Document>;
class Comparator {
public:
Comparator(const SortPattern& sortPattern) : _sort(sortPattern) {}
int operator()(const DocumentSorter::Data& lhs, const DocumentSorter::Data& rhs) const;
private:
const SortPattern& _sort;
};
SortOptions makeSortOptions() const;
SortPattern _sortPattern;
// A limit of zero is defined as no limit.
uint64_t _limit;
uint64_t _maxMemoryUsageBytes;
std::string _tempDir;
bool _diskUseAllowed = false;
std::unique_ptr<DocumentSorter> _sorter;
std::unique_ptr<DocumentSorter::Iterator> _output;
bool _isEOF = false;
bool _wasDiskUsed = false;
};
} // namespace mongo
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