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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 <boost/scoped_ptr.hpp>
#include <vector>
#include "mongo/db/diskloc.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/platform/unordered_set.h"
namespace mongo {
/**
* Reads from N children, each of which must have a valid DiskLoc. Uses a hash table to
* intersect the outputs of the N children, and outputs the intersection.
*
* Preconditions: Valid DiskLoc. More than one child.
*
* Any DiskLoc that we keep a reference to that is invalidated before we are able to return it
* is fetched and added to the WorkingSet as "flagged for further review." Because this stage
* operates with DiskLocs, we are unable to evaluate the AND for the invalidated DiskLoc, and it
* must be fully matched later.
*/
class AndHashStage : public PlanStage {
public:
AndHashStage(WorkingSet* ws, const MatchExpression* filter);
virtual ~AndHashStage();
void addChild(PlanStage* child);
virtual StageState work(WorkingSetID* out);
virtual bool isEOF();
virtual void prepareToYield();
virtual void recoverFromYield();
virtual void invalidate(const DiskLoc& dl);
virtual PlanStageStats* getStats();
private:
StageState readFirstChild();
StageState hashOtherChildren();
// Not owned by us.
WorkingSet* _ws;
// Not owned by us.
const MatchExpression* _filter;
// The stages we read from. Owned by us.
vector<PlanStage*> _children;
// _dataMap is filled out by the first child and probed by subsequent children.
typedef unordered_map<DiskLoc, WorkingSetID, DiskLoc::Hasher> DataMap;
DataMap _dataMap;
// Keeps track of what elements from _dataMap subsequent children have seen.
typedef unordered_set<DiskLoc, DiskLoc::Hasher> SeenMap;
SeenMap _seenMap;
// Iterator over the members of _dataMap that survive.
DataMap::iterator _resultIterator;
// True if we're still scanning _children for results.
bool _shouldScanChildren;
// Which child are we currently working on?
size_t _currentChild;
// Stats
CommonStats _commonStats;
AndHashStats _specificStats;
};
} // namespace mongo
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