text: /**
   *    Copyright (C) 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 "mongo/db/diskloc.h"
  #include "mongo/db/jsobj.h"
  #include "mongo/db/exec/plan_stage.h"
  #include "mongo/db/exec/working_set.h"
  #include "mongo/db/query/canonical_query.h"
  #include "mongo/db/query/query_solution.h"
  
  namespace mongo {
  
      /**
       * This stage outputs its mainChild, and possibly its backup child
       * and also updates the cache.
       *
       * Preconditions: Valid DiskLoc.
       *
       */
      class CachedPlanStage : public PlanStage {
      public:
          /**
           * Takes ownership of 'mainChild', 'mainQs', 'backupChild', and 'backupQs'.
           */
          CachedPlanStage(const Collection* collection,
                          CanonicalQuery* cq,
                          PlanStage* mainChild,
                          QuerySolution* mainQs,
                          PlanStage* backupChild = NULL,
                          QuerySolution* backupQs = NULL);
  
          virtual ~CachedPlanStage();
  
          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_CACHED_PLAN; }
  
          virtual PlanStageStats* getStats();
  
          virtual const CommonStats* getCommonStats();
  
          virtual const SpecificStats* getSpecificStats();
  
          static const char* kStageType;
  
      private:
          PlanStage* getActiveChild() const;
          void updateCache();
  
          // not owned
          const Collection* _collection;
  
          // not owned
          CanonicalQuery* _canonicalQuery;
  
          // Owned by us. Must be deleted after the corresponding PlanStage trees, as
          // those trees point into the query solutions.
          boost::scoped_ptr<QuerySolution> _mainQs;
          boost::scoped_ptr<QuerySolution> _backupQs;
  
          // Owned by us. Must be deleted before the QuerySolutions above, as these
          // can point into the QuerySolutions.
          boost::scoped_ptr<PlanStage> _mainChildPlan;
          boost::scoped_ptr<PlanStage> _backupChildPlan;
  
          // True if the main plan errors before producing results
          // and if a backup plan is available (can happen with blocking sorts)
          bool _usingBackupChild;
  
          // True if the childPlan has produced results yet.
          bool _alreadyProduced;
  
          // Have we updated the cache with our plan stats yet?
          bool _updatedCache;
  
          // Stats
          CommonStats _commonStats;
          CachedPlanStats _specificStats;
      };
  
  }  // namespace mongo
  