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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 <queue>
#include <vector>
#include "mongo/db/exec/working_set.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/parsed_query.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/query/plan_ranker.h"
#include "mongo/db/query/plan_executor.h"
#include "mongo/db/query/runner.h"
#include "mongo/platform/cstdint.h"
namespace mongo {
using std::queue;
using std::size_t;
using std::vector;
/**
* Runs several plans in parallel and picks the best one. Caches the selection for future use.
*/
class MultiPlanRunner : public Runner {
public:
/**
* Takes ownership of query.
*/
MultiPlanRunner(CanonicalQuery* query);
virtual ~MultiPlanRunner();
/**
* Takes ownership of all arguments
*/
void addPlan(QuerySolution* solution, PlanStage* root, WorkingSet* ws);
/**
* Get the next result. Yielding is handled internally. If a best plan is not picked when
* this is called, we call pickBestPlan() internally.
*/
Runner::RunnerState getNext(BSONObj* objOut);
/**
* Runs all plans added by addPlan, ranks them, and picks a best. Deletes all loser plans.
* All further calls to getNext(...) will return results from the best plan.
*
* Returns true if a best plan was picked, false if there was an error.
*
* If out is not-NULL, set *out to the index of the picked plan.
*/
bool pickBestPlan(size_t* out);
virtual void saveState();
virtual void restoreState();
virtual void invalidate(const DiskLoc& dl);
virtual const CanonicalQuery& getQuery() { return *_query; }
virtual void kill();
virtual bool forceYield();
private:
/**
* Have all our candidate plans do something.
*/
bool workAllPlans();
void yieldAllPlans();
void unyieldAllPlans();
// Did some plan fail? Just give up if so.
bool _failure;
// The winner...
scoped_ptr<PlanExecutor> _bestPlan;
// ...and any results it produced while working toward winning.
std::queue<WorkingSetID> _alreadyProduced;
// Candidate plans.
vector<CandidatePlan> _candidates;
// The query that we're trying to figure out the best solution to.
scoped_ptr<CanonicalQuery> _query;
// Were we killed during a yield?
bool _killed;
};
} // namespace mongo
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