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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 "mongo/db/diskloc.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
namespace mongo {
/**
* This stage turns a DiskLoc into a BSONObj.
*
* In WorkingSetMember terms, it transitions from LOC_AND_IDX to LOC_AND_UNOWNED_OBJ by reading
* the record at the provided loc. Returns verbatim any data that already has an object.
*
* Preconditions: Valid DiskLoc.
*/
class FetchStage : public PlanStage {
public:
FetchStage(WorkingSet* ws, PlanStage* child, const MatchExpression* filter);
virtual ~FetchStage();
virtual bool isEOF();
virtual StageState work(WorkingSetID* out);
virtual void prepareToYield();
virtual void recoverFromYield();
virtual void invalidate(const DiskLoc& dl);
PlanStageStats* getStats();
private:
/**
* If the member (with id memberID) passes our filter, set *out to memberID and return that
* ADVANCED. Otherwise, free memberID and return NEED_TIME.
*/
StageState returnIfMatches(WorkingSetMember* member, WorkingSetID memberID,
WorkingSetID* out);
/**
* work(...) delegates to this when we're called after requesting a fetch.
*/
StageState fetchCompleted(WorkingSetID* out);
// _ws is not owned by us.
WorkingSet* _ws;
scoped_ptr<PlanStage> _child;
// The filter is not owned by us.
const MatchExpression* _filter;
// If we're fetching a DiskLoc and it points at something that's not in memory, we return a
// a "please page this in" result and hold on to the WSID until the next call to work(...).
WorkingSetID _idBeingPagedIn;
// Stats
CommonStats _commonStats;
FetchStats _specificStats;
};
} // namespace mongo
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