diff options
Diffstat (limited to 'src/mongo/db/exec/multi_plan.h')
| -rw-r--r-- | src/mongo/db/exec/multi_plan.h | 368 |
1 files changed, 185 insertions, 183 deletions
diff --git a/src/mongo/db/exec/multi_plan.h b/src/mongo/db/exec/multi_plan.h index 189190163ca..28030fb8d34 100644 --- a/src/mongo/db/exec/multi_plan.h +++ b/src/mongo/db/exec/multi_plan.h @@ -41,192 +41,194 @@ namespace mongo { +/** + * This stage outputs its mainChild, and possibly it's backup child + * and also updates the cache. + * + * Preconditions: Valid RecordId. + * + * Owns the query solutions and PlanStage roots for all candidate plans. + */ +class MultiPlanStage : public PlanStage { +public: + /** + * Takes no ownership. + * + * If 'shouldCache' is true, writes a cache entry for the winning plan to the plan cache + * when possible. If 'shouldCache' is false, the plan cache will never be written. + */ + MultiPlanStage(OperationContext* txn, + const Collection* collection, + CanonicalQuery* cq, + bool shouldCache = true); + + virtual ~MultiPlanStage(); + + virtual bool isEOF(); + + virtual StageState work(WorkingSetID* out); + + virtual void saveState(); + + virtual void restoreState(OperationContext* opCtx); + + virtual void invalidate(OperationContext* txn, const RecordId& dl, InvalidationType type); + + virtual std::vector<PlanStage*> getChildren() const; + + virtual StageType stageType() const { + return STAGE_MULTI_PLAN; + } + + virtual PlanStageStats* getStats(); + + virtual const CommonStats* getCommonStats() const; + + virtual const SpecificStats* getSpecificStats() const; + + /** + * Takes ownership of QuerySolution and PlanStage. not of WorkingSet + */ + void addPlan(QuerySolution* solution, PlanStage* root, WorkingSet* sharedWs); + + /** + * Runs all plans added by addPlan, ranks them, and picks a best. + * All further calls to work(...) will return results from the best plan. + * + * If 'yieldPolicy' is non-NULL, then all locks may be yielded in between round-robin + * works of the candidate plans. By default, 'yieldPolicy' is NULL and no yielding will + * take place. + * + * Returns a non-OK status if the plan was killed during yield. + */ + Status pickBestPlan(PlanYieldPolicy* yieldPolicy); + + /** + * Returns the number of times that we are willing to work a plan during a trial period. + * + * Calculated based on a fixed query knob and the size of the collection. + */ + static size_t getTrialPeriodWorks(OperationContext* txn, const Collection* collection); + + /** + * Returns the max number of documents which we should allow any plan to return during the + * trial period. As soon as any plan hits this number of documents, the trial period ends. + */ + static size_t getTrialPeriodNumToReturn(const CanonicalQuery& query); + + /** Return true if a best plan has been chosen */ + bool bestPlanChosen() const; + + /** Return the index of the best plan chosen, for testing */ + int bestPlanIdx() const; + + /** + * Returns the QuerySolution for the best plan, or NULL if no best plan + * + * The MultiPlanStage retains ownership of the winning QuerySolution and returns an + * unowned pointer. + */ + QuerySolution* bestSolution(); + /** - * This stage outputs its mainChild, and possibly it's backup child - * and also updates the cache. + * Returns true if a backup plan was picked. + * This is the case when the best plan has a blocking stage. + * Exposed for testing. + */ + bool hasBackupPlan() const; + + // + // Used by explain. + // + + /** + * Gathers execution stats for all losing plans. Caller takes ownership of + * all pointers in the returned vector. + */ + std::vector<PlanStageStats*> generateCandidateStats(); + + static const char* kStageType; + +private: + // + // Have all our candidate plans do something. + // If all our candidate plans fail, *objOut will contain + // information on the failure. + // + + /** + * Calls work on each child plan in a round-robin fashion. We stop when any plan hits EOF + * or returns 'numResults' results. * - * Preconditions: Valid RecordId. + * Returns true if we need to keep working the plans and false otherwise. + */ + bool workAllPlans(size_t numResults, PlanYieldPolicy* yieldPolicy); + + /** + * Checks whether we need to perform either a timing-based yield or a yield for a document + * fetch. If so, then uses 'yieldPolicy' to actually perform the yield. * - * Owns the query solutions and PlanStage roots for all candidate plans. + * Returns a non-OK status if killed during a yield. */ - class MultiPlanStage : public PlanStage { - public: - /** - * Takes no ownership. - * - * If 'shouldCache' is true, writes a cache entry for the winning plan to the plan cache - * when possible. If 'shouldCache' is false, the plan cache will never be written. - */ - MultiPlanStage(OperationContext* txn, - const Collection* collection, - CanonicalQuery* cq, - bool shouldCache = true); - - virtual ~MultiPlanStage(); - - virtual bool isEOF(); - - virtual StageState work(WorkingSetID* out); - - virtual void saveState(); - - virtual void restoreState(OperationContext* opCtx); - - virtual void invalidate(OperationContext* txn, const RecordId& dl, InvalidationType type); - - virtual std::vector<PlanStage*> getChildren() const; - - virtual StageType stageType() const { return STAGE_MULTI_PLAN; } - - virtual PlanStageStats* getStats(); - - virtual const CommonStats* getCommonStats() const; - - virtual const SpecificStats* getSpecificStats() const; - - /** - * Takes ownership of QuerySolution and PlanStage. not of WorkingSet - */ - void addPlan(QuerySolution* solution, PlanStage* root, WorkingSet* sharedWs); - - /** - * Runs all plans added by addPlan, ranks them, and picks a best. - * All further calls to work(...) will return results from the best plan. - * - * If 'yieldPolicy' is non-NULL, then all locks may be yielded in between round-robin - * works of the candidate plans. By default, 'yieldPolicy' is NULL and no yielding will - * take place. - * - * Returns a non-OK status if the plan was killed during yield. - */ - Status pickBestPlan(PlanYieldPolicy* yieldPolicy); - - /** - * Returns the number of times that we are willing to work a plan during a trial period. - * - * Calculated based on a fixed query knob and the size of the collection. - */ - static size_t getTrialPeriodWorks(OperationContext* txn, const Collection* collection); - - /** - * Returns the max number of documents which we should allow any plan to return during the - * trial period. As soon as any plan hits this number of documents, the trial period ends. - */ - static size_t getTrialPeriodNumToReturn(const CanonicalQuery& query); - - /** Return true if a best plan has been chosen */ - bool bestPlanChosen() const; - - /** Return the index of the best plan chosen, for testing */ - int bestPlanIdx() const; - - /** - * Returns the QuerySolution for the best plan, or NULL if no best plan - * - * The MultiPlanStage retains ownership of the winning QuerySolution and returns an - * unowned pointer. - */ - QuerySolution* bestSolution(); - - /** - * Returns true if a backup plan was picked. - * This is the case when the best plan has a blocking stage. - * Exposed for testing. - */ - bool hasBackupPlan() const; - - // - // Used by explain. - // - - /** - * Gathers execution stats for all losing plans. Caller takes ownership of - * all pointers in the returned vector. - */ - std::vector<PlanStageStats*> generateCandidateStats(); - - static const char* kStageType; - - private: - // - // Have all our candidate plans do something. - // If all our candidate plans fail, *objOut will contain - // information on the failure. - // - - /** - * Calls work on each child plan in a round-robin fashion. We stop when any plan hits EOF - * or returns 'numResults' results. - * - * Returns true if we need to keep working the plans and false otherwise. - */ - bool workAllPlans(size_t numResults, PlanYieldPolicy* yieldPolicy); - - /** - * Checks whether we need to perform either a timing-based yield or a yield for a document - * fetch. If so, then uses 'yieldPolicy' to actually perform the yield. - * - * Returns a non-OK status if killed during a yield. - */ - Status tryYield(PlanYieldPolicy* yieldPolicy); - - static const int kNoSuchPlan = -1; - - // Not owned here. - OperationContext* _txn; - - // Not owned here. Must be non-null. - const Collection* _collection; - - // Whether or not we should try to cache the winning plan in the plan cache. - const bool _shouldCache; - - // The query that we're trying to figure out the best solution to. - // not owned here - CanonicalQuery* _query; - - // Candidate plans. Each candidate includes a child PlanStage tree and QuerySolution which - // are owned here. Ownership of all QuerySolutions is retained here, and will *not* be - // tranferred to the PlanExecutor that wraps this stage. - std::vector<CandidatePlan> _candidates; - - // index into _candidates, of the winner of the plan competition - // uses -1 / kNoSuchPlan when best plan is not (yet) known - int _bestPlanIdx; - - // index into _candidates, of the backup plan for sort - // uses -1 / kNoSuchPlan when best plan is not (yet) known - int _backupPlanIdx; - - // Set if this MultiPlanStage cannot continue, and the query must fail. This can happen in - // two ways. The first is that all candidate plans fail. Note that one plan can fail - // during normal execution of the plan competition. Here is an example: - // - // Plan 1: collection scan with sort. Sort runs out of memory. - // Plan 2: ixscan that provides sort. Won't run out of memory. - // - // We want to choose plan 2 even if plan 1 fails. - // - // The second way for failure to occur is that the execution of this query is killed during - // a yield, by some concurrent event such as a collection drop. - bool _failure; - - // If everything fails during the plan competition, we can't pick one. - size_t _failureCount; - - // if pickBestPlan fails, this is set to the wsid of the statusMember - // returned by ::work() - WorkingSetID _statusMemberId; - - // When a stage requests a yield for document fetch, it gives us back a RecordFetcher* - // to use to pull the record into memory. We take ownership of the RecordFetcher here, - // deleting it after we've had a chance to do the fetch. For timing-based yields, we - // just pass a NULL fetcher. - std::unique_ptr<RecordFetcher> _fetcher; - - // Stats - CommonStats _commonStats; - MultiPlanStats _specificStats; - }; + Status tryYield(PlanYieldPolicy* yieldPolicy); + + static const int kNoSuchPlan = -1; + + // Not owned here. + OperationContext* _txn; + + // Not owned here. Must be non-null. + const Collection* _collection; + + // Whether or not we should try to cache the winning plan in the plan cache. + const bool _shouldCache; + + // The query that we're trying to figure out the best solution to. + // not owned here + CanonicalQuery* _query; + + // Candidate plans. Each candidate includes a child PlanStage tree and QuerySolution which + // are owned here. Ownership of all QuerySolutions is retained here, and will *not* be + // tranferred to the PlanExecutor that wraps this stage. + std::vector<CandidatePlan> _candidates; + + // index into _candidates, of the winner of the plan competition + // uses -1 / kNoSuchPlan when best plan is not (yet) known + int _bestPlanIdx; + + // index into _candidates, of the backup plan for sort + // uses -1 / kNoSuchPlan when best plan is not (yet) known + int _backupPlanIdx; + + // Set if this MultiPlanStage cannot continue, and the query must fail. This can happen in + // two ways. The first is that all candidate plans fail. Note that one plan can fail + // during normal execution of the plan competition. Here is an example: + // + // Plan 1: collection scan with sort. Sort runs out of memory. + // Plan 2: ixscan that provides sort. Won't run out of memory. + // + // We want to choose plan 2 even if plan 1 fails. + // + // The second way for failure to occur is that the execution of this query is killed during + // a yield, by some concurrent event such as a collection drop. + bool _failure; + + // If everything fails during the plan competition, we can't pick one. + size_t _failureCount; + + // if pickBestPlan fails, this is set to the wsid of the statusMember + // returned by ::work() + WorkingSetID _statusMemberId; + + // When a stage requests a yield for document fetch, it gives us back a RecordFetcher* + // to use to pull the record into memory. We take ownership of the RecordFetcher here, + // deleting it after we've had a chance to do the fetch. For timing-based yields, we + // just pass a NULL fetcher. + std::unique_ptr<RecordFetcher> _fetcher; + + // Stats + CommonStats _commonStats; + MultiPlanStats _specificStats; +}; } // namespace mongo |