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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/>.
*
* 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 <queue>
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/working_set.h"
namespace mongo {
class RecordId;
/**
* QueuedDataStage is a data-producing stage. Unlike the other two leaf stages (CollectionScan
* and IndexScan) QueuedDataStage does not require any underlying storage layer.
*
* A QueuedDataStage is "programmed" by pushing return values from work() onto its internal
* queue. Calls to QueuedDataStage::work() pop values off that queue and return them in FIFO
* order, annotating the working set with data when appropriate.
*/
class QueuedDataStage : public PlanStage {
public:
QueuedDataStage(WorkingSet* ws);
virtual ~QueuedDataStage() { }
virtual StageState work(WorkingSetID* out);
virtual bool isEOF();
// These don't really mean anything here.
// Some day we could count the # of calls to the yield functions to check that other stages
// have correct yielding behavior.
virtual void saveState();
virtual void restoreState(OperationContext* opCtx);
virtual void invalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
virtual std::vector<PlanStage*> getChildren() const;
virtual StageType stageType() const { return STAGE_QUEUED_DATA; }
//
// Exec stats
//
virtual PlanStageStats* getStats();
virtual const CommonStats* getCommonStats() const;
virtual const SpecificStats* getSpecificStats() const;
/**
* Add a result to the back of the queue.
*
* Note: do not add PlanStage::ADVANCED with this method, ADVANCED can
* only be added with a data member.
*
* Work() goes through the queue.
* Either no data is returned (just a state), or...
*/
void pushBack(const PlanStage::StageState state);
/**
* ...data is returned (and we ADVANCED)
*
* Allocates a new member and copies 'member' into it.
* Does not take ownership of anything in 'member'.
*/
void pushBack(const WorkingSetMember& member);
static const char* kStageType;
private:
// We don't own this.
WorkingSet* _ws;
// The data we return.
std::queue<PlanStage::StageState> _results;
std::queue<WorkingSetID> _members;
// Stats
CommonStats _commonStats;
MockStats _specificStats;
};
} // namespace mongo
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