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/**
* Copyright (C) 2013-2014 MongoDB 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 <boost/scoped_ptr.hpp>
#include <string>
#include <queue>
#include "mongo/base/status.h"
#include "mongo/db/diskloc.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/query/query_planner_params.h"
#include "mongo/db/query/query_solution.h"
namespace mongo {
class OperationContext;
/**
* The SubplanStage is used for rooted $or queries. It plans each clause of the $or
* individually, and then creates an overall query plan based on the winning plan from
* each clause.
*
* Uses the MultiPlanStage in order to rank plans for the individual clauses.
*/
class SubplanStage : public PlanStage {
public:
/**
* Used to create SubplanStage instances. The caller owns the instance
* returned through 'out'.
*
* 'out' is valid only if an OK status is returned.
*/
static Status make(OperationContext* txn,
Collection* collection,
WorkingSet* ws,
const QueryPlannerParams& params,
CanonicalQuery* cq,
SubplanStage** out);
virtual ~SubplanStage();
static bool canUseSubplanning(const CanonicalQuery& query);
virtual bool isEOF();
virtual StageState work(WorkingSetID* out);
virtual void saveState();
virtual void restoreState(OperationContext* opCtx);
virtual void invalidate(const DiskLoc& dl, InvalidationType type);
virtual std::vector<PlanStage*> getChildren() const;
virtual StageType stageType() const { return STAGE_SUBPLAN; }
PlanStageStats* getStats();
virtual const CommonStats* getCommonStats();
virtual const SpecificStats* getSpecificStats();
static const char* kStageType;
private:
SubplanStage(OperationContext* txn,
Collection* collection,
WorkingSet* ws,
const QueryPlannerParams& params,
CanonicalQuery* cq);
/**
* Plan each branch of the $or independently, and store the resulting
* lists of query solutions in '_solutions'.
*
* Called from SubplanStage::make so that construction of the subplan stage
* fails immediately, rather than returning a plan executor and subsequently
* through getNext(...).
*/
Status planSubqueries();
/**
* Uses the query planning results from planSubqueries() and the multi plan stage
* to select the best plan for each branch.
*/
Status pickBestPlan();
// transactional context for read locks. Not owned by us
OperationContext* _txn;
Collection* _collection;
// Not owned here.
WorkingSet* _ws;
QueryPlannerParams _plannerParams;
// Not owned here.
CanonicalQuery* _query;
bool _killed;
boost::scoped_ptr<PlanStage> _child;
// We do the subquery planning up front, and keep the resulting
// query solutions here. Lists of query solutions are dequeued
// and ownership is transferred to the underlying runners one
// at a time.
std::queue< std::vector<QuerySolution*> > _solutions;
// Holds the canonicalized subqueries. Ownership is transferred
// to the underlying runners one at a time.
std::queue<CanonicalQuery*> _cqs;
// We need this to extract cache-friendly index data from the index assignments.
map<BSONObj, size_t> _indexMap;
CommonStats _commonStats;
};
} // namespace mongo
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