diff options
Diffstat (limited to 'src/mongo/db/exec/subplan.h')
| -rw-r--r-- | src/mongo/db/exec/subplan.h | 285 |
1 files changed, 144 insertions, 141 deletions
diff --git a/src/mongo/db/exec/subplan.h b/src/mongo/db/exec/subplan.h index f46a25b3bc8..ca831a1856e 100644 --- a/src/mongo/db/exec/subplan.h +++ b/src/mongo/db/exec/subplan.h @@ -42,154 +42,157 @@ namespace mongo { - class OperationContext; +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. + * + * Notes on caching strategy: + * + * --Interaction with the plan cache is done on a per-clause basis. For a given clause C, + * if there is a plan in the cache for shape C, then C is planned using the index tags + * obtained from the plan cache entry. If no cached plan is found for C, then a MultiPlanStage + * is used to determine the best plan for the clause; unless there is a tie between multiple + * candidate plans, the winner is inserted into the plan cache and used to plan subsequent + * executions of C. These subsequent executions of shape C could be either as a clause in + * another rooted $or query, or shape C as its own query. + * + * --Plans for entire rooted $or queries are neither written to nor read from the plan cache. + */ +class SubplanStage : public PlanStage { +public: + SubplanStage(OperationContext* txn, + Collection* collection, + WorkingSet* ws, + const QueryPlannerParams& params, + CanonicalQuery* cq); + + 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(OperationContext* txn, const RecordId& dl, InvalidationType type); + + virtual std::vector<PlanStage*> getChildren() const; + + virtual StageType stageType() const { + return STAGE_SUBPLAN; + } + + PlanStageStats* getStats(); + + virtual const CommonStats* getCommonStats() const; + + virtual const SpecificStats* getSpecificStats() const; + + static const char* kStageType; /** - * 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. + * Selects a plan using subplanning. First uses the query planning results from + * planSubqueries() and the multi plan stage to select the best plan for each branch. * - * Uses the MultiPlanStage in order to rank plans for the individual clauses. + * If this effort fails, then falls back on planning the whole query normally rather + * then planning $or branches independently. * - * Notes on caching strategy: + * 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. * - * --Interaction with the plan cache is done on a per-clause basis. For a given clause C, - * if there is a plan in the cache for shape C, then C is planned using the index tags - * obtained from the plan cache entry. If no cached plan is found for C, then a MultiPlanStage - * is used to determine the best plan for the clause; unless there is a tie between multiple - * candidate plans, the winner is inserted into the plan cache and used to plan subsequent - * executions of C. These subsequent executions of shape C could be either as a clause in - * another rooted $or query, or shape C as its own query. - * - * --Plans for entire rooted $or queries are neither written to nor read from the plan cache. + * Returns a non-OK status if the plan was killed during yield or if planning fails. + */ + Status pickBestPlan(PlanYieldPolicy* yieldPolicy); + + // + // For testing. + // + + /** + * Returns true if the i-th branch was planned by retrieving a cached solution, + * otherwise returns false. + */ + bool branchPlannedFromCache(size_t i) const; + +private: + /** + * A class used internally in order to keep track of the results of planning + * a particular $or branch. */ - class SubplanStage : public PlanStage { + struct BranchPlanningResult { + MONGO_DISALLOW_COPYING(BranchPlanningResult); + public: - SubplanStage(OperationContext* txn, - Collection* collection, - WorkingSet* ws, - const QueryPlannerParams& params, - CanonicalQuery* cq); - - 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(OperationContext* txn, const RecordId& dl, InvalidationType type); - - virtual std::vector<PlanStage*> getChildren() const; - - virtual StageType stageType() const { return STAGE_SUBPLAN; } - - PlanStageStats* getStats(); - - virtual const CommonStats* getCommonStats() const; - - virtual const SpecificStats* getSpecificStats() const; - - static const char* kStageType; - - /** - * Selects a plan using subplanning. First uses the query planning results from - * planSubqueries() and the multi plan stage to select the best plan for each branch. - * - * If this effort fails, then falls back on planning the whole query normally rather - * then planning $or branches independently. - * - * 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 or if planning fails. - */ - Status pickBestPlan(PlanYieldPolicy* yieldPolicy); - - // - // For testing. - // - - /** - * Returns true if the i-th branch was planned by retrieving a cached solution, - * otherwise returns false. - */ - bool branchPlannedFromCache(size_t i) const; - - private: - /** - * A class used internally in order to keep track of the results of planning - * a particular $or branch. - */ - struct BranchPlanningResult { - MONGO_DISALLOW_COPYING(BranchPlanningResult); - public: - BranchPlanningResult() { } - - // A parsed version of one branch of the $or. - std::unique_ptr<CanonicalQuery> canonicalQuery; - - // If there is cache data available, then we store it here rather than generating - // a set of alternate plans for the branch. The index tags from the cache data - // can be applied directly to the parent $or MatchExpression when generating the - // composite solution. - std::unique_ptr<CachedSolution> cachedSolution; - - // Query solutions resulting from planning the $or branch. - OwnedPointerVector<QuerySolution> solutions; - }; - - /** - * 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. - * - * Helper for pickBestPlan(). - */ - Status choosePlanForSubqueries(PlanYieldPolicy* yieldPolicy); - - /** - * Used as a fallback if subplanning fails. Helper for pickBestPlan(). - */ - Status choosePlanWholeQuery(PlanYieldPolicy* yieldPolicy); - - // transactional context for read locks. Not owned by us - OperationContext* _txn; - - // Not owned here. Must be non-null. - Collection* _collection; - - // Not owned here. - WorkingSet* _ws; - - QueryPlannerParams _plannerParams; - - // Not owned here. - CanonicalQuery* _query; - - // If we successfully create a "composite solution" by planning each $or branch - // independently, that solution is owned here. - std::unique_ptr<QuerySolution> _compositeSolution; - - std::unique_ptr<PlanStage> _child; - - // Holds a list of the results from planning each branch. - OwnedPointerVector<BranchPlanningResult> _branchResults; - - // We need this to extract cache-friendly index data from the index assignments. - std::map<BSONObj, size_t> _indexMap; - - CommonStats _commonStats; + BranchPlanningResult() {} + + // A parsed version of one branch of the $or. + std::unique_ptr<CanonicalQuery> canonicalQuery; + + // If there is cache data available, then we store it here rather than generating + // a set of alternate plans for the branch. The index tags from the cache data + // can be applied directly to the parent $or MatchExpression when generating the + // composite solution. + std::unique_ptr<CachedSolution> cachedSolution; + + // Query solutions resulting from planning the $or branch. + OwnedPointerVector<QuerySolution> solutions; }; + /** + * 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. + * + * Helper for pickBestPlan(). + */ + Status choosePlanForSubqueries(PlanYieldPolicy* yieldPolicy); + + /** + * Used as a fallback if subplanning fails. Helper for pickBestPlan(). + */ + Status choosePlanWholeQuery(PlanYieldPolicy* yieldPolicy); + + // transactional context for read locks. Not owned by us + OperationContext* _txn; + + // Not owned here. Must be non-null. + Collection* _collection; + + // Not owned here. + WorkingSet* _ws; + + QueryPlannerParams _plannerParams; + + // Not owned here. + CanonicalQuery* _query; + + // If we successfully create a "composite solution" by planning each $or branch + // independently, that solution is owned here. + std::unique_ptr<QuerySolution> _compositeSolution; + + std::unique_ptr<PlanStage> _child; + + // Holds a list of the results from planning each branch. + OwnedPointerVector<BranchPlanningResult> _branchResults; + + // We need this to extract cache-friendly index data from the index assignments. + std::map<BSONObj, size_t> _indexMap; + + CommonStats _commonStats; +}; + } // namespace mongo |