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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 <deque>
#include "mongo/db/namespace_string.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/document_source_limit.h"
#include "mongo/db/query/plan_summary_stats.h"
namespace mongo {
class PlanExecutor;
/**
* Constructs and returns Documents from the BSONObj objects produced by a supplied
* PlanExecutor.
*
* An object of this type may only be used by one thread, see SERVER-6123.
*/
class DocumentSourceCursor final : public DocumentSource {
public:
// virtuals from DocumentSource
GetNextResult getNext() final;
const char* getSourceName() const final;
BSONObjSet getOutputSorts() final {
return _outputSorts;
}
/**
* Attempts to combine with any subsequent $limit stages by setting the internal '_limit' field.
*/
Pipeline::SourceContainer::iterator doOptimizeAt(Pipeline::SourceContainer::iterator itr,
Pipeline::SourceContainer* container) final;
Value serialize(bool explain = false) const final;
bool isValidInitialSource() const final {
return true;
}
void dispose() final;
void detachFromOperationContext() final;
void reattachToOperationContext(OperationContext* opCtx) final;
/**
* Create a document source based on a passed-in PlanExecutor.
*
* This is usually put at the beginning of a chain of document sources
* in order to fetch data from the database.
*/
static boost::intrusive_ptr<DocumentSourceCursor> create(
const std::string& ns,
std::unique_ptr<PlanExecutor> exec,
const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
/*
Record the query that was specified for the cursor this wraps, if
any.
This should be captured after any optimizations are applied to
the pipeline so that it reflects what is really used.
This gets used for explain output.
@param pBsonObj the query to record
*/
void setQuery(const BSONObj& query) {
_query = query;
}
/*
Record the sort that was specified for the cursor this wraps, if
any.
This should be captured after any optimizations are applied to
the pipeline so that it reflects what is really used.
This gets used for explain output.
@param pBsonObj the sort to record
*/
void setSort(const BSONObj& sort) {
_sort = sort;
}
/**
* Informs this object of projection and dependency information.
*
* @param projection The projection that has been passed down to the query system.
* @param deps The output of DepsTracker::toParsedDeps.
*/
void setProjection(const BSONObj& projection, const boost::optional<ParsedDeps>& deps);
/// returns -1 for no limit
long long getLimit() const;
/**
* If subsequent sources need no information from the cursor, the cursor can simply output empty
* documents, avoiding the overhead of converting BSONObjs to Documents.
*/
void shouldProduceEmptyDocs() {
_shouldProduceEmptyDocs = true;
}
const std::string& getPlanSummaryStr() const;
const PlanSummaryStats& getPlanSummaryStats() const;
protected:
void doInjectExpressionContext() final;
private:
DocumentSourceCursor(const std::string& ns,
std::unique_ptr<PlanExecutor> exec,
const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
void loadBatch();
void recordPlanSummaryStr();
void recordPlanSummaryStats();
std::deque<Document> _currentBatch;
// BSONObj members must outlive _projection and cursor.
BSONObj _query;
BSONObj _sort;
BSONObj _projection;
bool _shouldProduceEmptyDocs = false;
boost::optional<ParsedDeps> _dependencies;
boost::intrusive_ptr<DocumentSourceLimit> _limit;
long long _docsAddedToBatches; // for _limit enforcement
const NamespaceString _nss;
std::unique_ptr<PlanExecutor> _exec;
BSONObjSet _outputSorts;
std::string _planSummary;
PlanSummaryStats _planSummaryStats;
};
} // namespace mongo
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