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/**
* Copyright (C) 2016 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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_source.h"
#include "mongo/db/pipeline/document_source_limit.h"
#include "mongo/db/sorter/sorter.h"
namespace mongo {
class Expression;
class DocumentSourceSort final : public DocumentSource, public SplittableDocumentSource {
public:
static const uint64_t kMaxMemoryUsageBytes = 100 * 1024 * 1024;
// virtuals from DocumentSource
GetNextResult getNext() final;
const char* getSourceName() const final;
void serializeToArray(
std::vector<Value>& array,
boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final;
GetModPathsReturn getModifiedPaths() const final {
// A $sort does not modify any paths.
return {GetModPathsReturn::Type::kFiniteSet, std::set<std::string>{}};
}
bool canSwapWithMatch() const final {
return true;
}
BSONObjSet getOutputSorts() final {
return allPrefixes(_sort);
}
/**
* Attempts to absorb a subsequent $limit stage so that it an perform a top-k sort.
*/
Pipeline::SourceContainer::iterator doOptimizeAt(Pipeline::SourceContainer::iterator itr,
Pipeline::SourceContainer* container) final;
void dispose() final;
GetDepsReturn getDependencies(DepsTracker* deps) const final;
boost::intrusive_ptr<DocumentSource> getShardSource() final;
boost::intrusive_ptr<DocumentSource> getMergeSource() final;
/// Write out a Document whose contents are the sort key.
Document serializeSortKey(bool explain) const;
/**
* Parses a $sort stage from the user-supplied BSON.
*/
static boost::intrusive_ptr<DocumentSource> createFromBson(
BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
/**
* Convenience method for creating a $sort stage.
*/
static boost::intrusive_ptr<DocumentSourceSort> create(
const boost::intrusive_ptr<ExpressionContext>& pExpCtx,
BSONObj sortOrder,
long long limit = -1,
uint64_t maxMemoryUsageBytes = kMaxMemoryUsageBytes);
/**
* Returns -1 for no limit.
*/
long long getLimit() const;
/**
* Loads a document to be sorted. This can be used to sort a stream of documents that are not
* coming from another DocumentSource. Once all documents have been added, the caller must call
* loadingDone() before using getNext() to receive the documents in sorted order.
*/
void loadDocument(const Document& doc);
/**
* Signals to the sort stage that there will be no more input documents. It is an error to call
* loadDocument() once this method returns.
*/
void loadingDone();
/**
* Instructs the sort stage to use the given set of cursors as inputs, to merge documents that
* have already been sorted.
*/
void populateFromCursors(const std::vector<DBClientCursor*>& cursors);
bool isPopulated() {
return _populated;
};
boost::intrusive_ptr<DocumentSourceLimit> getLimitSrc() const {
return limitSrc;
}
private:
explicit DocumentSourceSort(const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
Value serialize(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final {
MONGO_UNREACHABLE; // Should call serializeToArray instead.
}
/**
* Helper to add a sort key to this stage.
*/
void addKey(StringData fieldPath, bool ascending);
/**
* Before returning anything, we have to consume all input and sort it. This method consumes all
* input and prepares the sorted stream '_output'.
*
* This method may not be able to finish populating the sorter in a single call if 'pSource'
* returns a DocumentSource::GetNextResult::kPauseExecution, so it returns the last
* GetNextResult encountered, which may be either kEOF or kPauseExecution.
*/
GetNextResult populate();
bool _populated = false;
BSONObj _sort;
SortOptions makeSortOptions() const;
// This is used to merge pre-sorted results from a DocumentSourceMergeCursors.
class IteratorFromCursor;
/* these two parallel each other */
typedef std::vector<boost::intrusive_ptr<Expression>> SortKey;
SortKey vSortKey;
std::vector<char> vAscending; // used like std::vector<bool> but without specialization
/// Extracts the fields in vSortKey from the Document;
Value extractKey(const Document& d) const;
/// Compare two Values according to the specified sort key.
int compare(const Value& lhs, const Value& rhs) const;
typedef Sorter<Value, Document> MySorter;
/**
* Absorbs 'limit', enabling a top-k sort. It is safe to call this multiple times, it will keep
* the smallest limit.
*/
void setLimitSrc(boost::intrusive_ptr<DocumentSourceLimit> limit) {
if (!limitSrc || limit->getLimit() < limitSrc->getLimit()) {
limitSrc = limit;
}
}
// For MySorter
class Comparator {
public:
explicit Comparator(const DocumentSourceSort& source) : _source(source) {}
int operator()(const MySorter::Data& lhs, const MySorter::Data& rhs) const {
return _source.compare(lhs.first, rhs.first);
}
private:
const DocumentSourceSort& _source;
};
boost::intrusive_ptr<DocumentSourceLimit> limitSrc;
uint64_t _maxMemoryUsageBytes;
bool _done;
bool _mergingPresorted;
std::unique_ptr<MySorter> _sorter;
std::unique_ptr<MySorter::Iterator> _output;
};
} // namespace mongo
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