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/**
* Copyright (C) 2013 10gen 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/>.
*/
#pragma once
#include "mongo/db/diskloc.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/exec/plan_stage.h"
namespace mongo {
/**
* This stage implements limit functionality. It only returns 'limit' results before EOF.
*
* Sort has a baked-in limit, as it can optimize the sort if it has a limit.
*
* Preconditions: None.
*/
class LimitStage : public PlanStage {
public:
LimitStage(int limit, WorkingSet* ws, PlanStage* child);
virtual ~LimitStage();
virtual bool isEOF();
virtual StageState work(WorkingSetID* out);
virtual void prepareToYield();
virtual void recoverFromYield();
virtual void invalidate(const DiskLoc& dl);
virtual PlanStageStats* getStats();
private:
WorkingSet* _ws;
scoped_ptr<PlanStage> _child;
// We only return this many results.
int _numToReturn;
// Stats
CommonStats _commonStats;
};
} // namespace mongo
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