SERVER-19456 Use final designators where appropriate in PlanStages

38 files changed, 297 insertions, 328 deletions

diff --git a/src/mongo/db/exec/and_hash.h b/src/mongo/db/exec/and_hash.h
index b72a78fbeb8..9f42f93d5e1 100644
--- a/src/mongo/db/exec/and_hash.h
+++ b/src/mongo/db/exec/and_hash.h
@@ -49,7 +49,7 @@ namespace mongo {
  * operates with RecordIds, we are unable to evaluate the AND for the invalidated RecordId, and it
  * must be fully matched later.
  */
-class AndHashStage : public PlanStage {
+class AndHashStage final : public PlanStage {
 public:
     AndHashStage(WorkingSet* ws, const Collection* collection);
 
@@ -66,18 +66,18 @@ public:
      */
     size_t getMemUsage() const;
 
-    virtual StageState work(WorkingSetID* out);
-    virtual bool isEOF();
+    StageState work(WorkingSetID* out) final;
+    bool isEOF() final;
 
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_AND_HASH;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/and_sorted.h b/src/mongo/db/exec/and_sorted.h
index b742a1090e3..ca6ea3e7410 100644
--- a/src/mongo/db/exec/and_sorted.h
+++ b/src/mongo/db/exec/and_sorted.h
@@ -51,24 +51,24 @@ namespace mongo {
  * operates with RecordIds, we are unable to evaluate the AND for the invalidated RecordId, and it
  * must be fully matched later.
  */
-class AndSortedStage : public PlanStage {
+class AndSortedStage final : public PlanStage {
 public:
     AndSortedStage(WorkingSet* ws, const Collection* collection);
 
     void addChild(PlanStage* child);
 
-    virtual StageState work(WorkingSetID* out);
-    virtual bool isEOF();
+    StageState work(WorkingSetID* out) final;
+    bool isEOF() final;
 
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_AND_SORTED;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/cached_plan.h b/src/mongo/db/exec/cached_plan.h
index 7cf4a1ebc88..5216e33eac0 100644
--- a/src/mongo/db/exec/cached_plan.h
+++ b/src/mongo/db/exec/cached_plan.h
@@ -51,7 +51,7 @@ class PlanYieldPolicy;
  * Preconditions: Valid RecordId.
  *
  */
-class CachedPlanStage : public PlanStage {
+class CachedPlanStage final : public PlanStage {
 public:
     CachedPlanStage(OperationContext* txn,
                     Collection* collection,
@@ -61,20 +61,20 @@ public:
                     size_t decisionWorks,
                     PlanStage* root);
 
-    virtual bool isEOF();
+    bool isEOF() final;
 
-    virtual StageState work(WorkingSetID* out);
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doReattachToOperationContext(OperationContext* opCtx) final;
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_CACHED_PLAN;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/collection_scan.h b/src/mongo/db/exec/collection_scan.h
index e08d583a7a3..2cfac584456 100644
--- a/src/mongo/db/exec/collection_scan.h
+++ b/src/mongo/db/exec/collection_scan.h
@@ -47,29 +47,29 @@ class OperationContext;
  *
  * Preconditions: Valid RecordId.
  */
-class CollectionScan : public PlanStage {
+class CollectionScan final : public PlanStage {
 public:
     CollectionScan(OperationContext* txn,
                    const CollectionScanParams& params,
                    WorkingSet* workingSet,
                    const MatchExpression* filter);
 
-    virtual StageState work(WorkingSetID* out);
-    virtual bool isEOF();
+    StageState work(WorkingSetID* out) final;
+    bool isEOF() final;
 
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
-    virtual void doSaveState();
-    virtual void doRestoreState();
-    virtual void doDetachFromOperationContext();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
+    void doSaveState() final;
+    void doRestoreState() final;
+    void doDetachFromOperationContext() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_COLLSCAN;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/count.h b/src/mongo/db/exec/count.h
index 110c9923119..b84f0bbe498 100644
--- a/src/mongo/db/exec/count.h
+++ b/src/mongo/db/exec/count.h
@@ -45,7 +45,7 @@ namespace mongo {
  * Only returns NEED_TIME until hitting EOF. The count result can be obtained by examining
  * the specific stats.
  */
-class CountStage : public PlanStage {
+class CountStage final : public PlanStage {
 public:
     CountStage(OperationContext* txn,
                Collection* collection,
@@ -53,18 +53,18 @@ public:
                WorkingSet* ws,
                PlanStage* child);
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_COUNT;
     }
 
     std::unique_ptr<PlanStageStats> getStats();
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/count_scan.h b/src/mongo/db/exec/count_scan.h
index dbbd85c5715..f7f65700134 100644
--- a/src/mongo/db/exec/count_scan.h
+++ b/src/mongo/db/exec/count_scan.h
@@ -64,25 +64,25 @@ struct CountScanParams {
  * Only created through the getExecutorCount path, as count is the only operation that doesn't
  * care about its data.
  */
-class CountScan : public PlanStage {
+class CountScan final : public PlanStage {
 public:
     CountScan(OperationContext* txn, const CountScanParams& params, WorkingSet* workingSet);
 
-    virtual StageState work(WorkingSetID* out);
-    virtual bool isEOF();
-    virtual void doSaveState();
-    virtual void doRestoreState();
-    virtual void doDetachFromOperationContext();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    StageState work(WorkingSetID* out) final;
+    bool isEOF() final;
+    void doSaveState() final;
+    void doRestoreState() final;
+    void doDetachFromOperationContext() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_COUNT_SCAN;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/delete.h b/src/mongo/db/exec/delete.h
index 1b85a37474d..528bad31088 100644
--- a/src/mongo/db/exec/delete.h
+++ b/src/mongo/db/exec/delete.h
@@ -76,7 +76,7 @@ struct DeleteStageParams {
  * Callers of work() must be holding a write lock (and, for shouldCallLogOp=true deletes,
  * callers must have had the replication coordinator approve the write).
  */
-class DeleteStage : public PlanStage {
+class DeleteStage final : public PlanStage {
     MONGO_DISALLOW_COPYING(DeleteStage);
 
 public:
@@ -86,19 +86,19 @@ public:
                 Collection* collection,
                 PlanStage* child);
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doRestoreState();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    void doRestoreState() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_DELETE;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/distinct_scan.h b/src/mongo/db/exec/distinct_scan.h
index 36b20477a24..6caafeae2ff 100644
--- a/src/mongo/db/exec/distinct_scan.h
+++ b/src/mongo/db/exec/distinct_scan.h
@@ -72,25 +72,24 @@ struct DistinctParams {
  *
  * Only created through the getExecutorDistinct path.  See db/query/get_executor.cpp
  */
-class DistinctScan : public PlanStage {
+class DistinctScan final : public PlanStage {
 public:
     DistinctScan(OperationContext* txn, const DistinctParams& params, WorkingSet* workingSet);
-    virtual ~DistinctScan() {}
 
-    virtual StageState work(WorkingSetID* out);
-    virtual bool isEOF();
-    virtual void doSaveState();
-    virtual void doRestoreState();
-    virtual void doDetachFromOperationContext();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    StageState work(WorkingSetID* out) final;
+    bool isEOF() final;
+    void doSaveState() final;
+    void doRestoreState() final;
+    void doDetachFromOperationContext() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_DISTINCT_SCAN;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/eof.h b/src/mongo/db/exec/eof.h
index 30df7679ba1..33462ca3aa9 100644
--- a/src/mongo/db/exec/eof.h
+++ b/src/mongo/db/exec/eof.h
@@ -36,23 +36,23 @@ namespace mongo {
 /**
  * This stage just returns EOF immediately.
  */
-class EOFStage : public PlanStage {
+class EOFStage final : public PlanStage {
 public:
     EOFStage();
 
-    virtual ~EOFStage();
+    ~EOFStage();
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_EOF;
     }
 
     std::unique_ptr<PlanStageStats> getStats();
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 };
diff --git a/src/mongo/db/exec/fetch.h b/src/mongo/db/exec/fetch.h
index 4e1bffcdeda..4cb2c37bca4 100644
--- a/src/mongo/db/exec/fetch.h
+++ b/src/mongo/db/exec/fetch.h
@@ -55,24 +55,24 @@ public:
                const MatchExpression* filter,
                const Collection* collection);
 
-    virtual ~FetchStage();
+    ~FetchStage();
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doSaveState();
-    virtual void doRestoreState();
-    virtual void doDetachFromOperationContext();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doSaveState() final;
+    void doRestoreState() final;
+    void doDetachFromOperationContext() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_FETCH;
     }
 
     std::unique_ptr<PlanStageStats> getStats();
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/filter.h b/src/mongo/db/exec/filter.h
index e23e116dfd9..40e1af14b1c 100644
--- a/src/mongo/db/exec/filter.h
+++ b/src/mongo/db/exec/filter.h
@@ -42,7 +42,6 @@ namespace mongo {
 class WorkingSetMatchableDocument : public MatchableDocument {
 public:
     WorkingSetMatchableDocument(WorkingSetMember* wsm) : _wsm(wsm) {}
-    virtual ~WorkingSetMatchableDocument() {}
 
     // This is only called by a $where query.  The query system must be smart enough to realize
     // that it should do a fetch beforehand.
@@ -51,7 +50,7 @@ public:
         return _wsm->obj.value();
     }
 
-    virtual ElementIterator* allocateIterator(const ElementPath* path) const {
+    ElementIterator* allocateIterator(const ElementPath* path) const final {
         // BSONElementIterator does some interesting things with arrays that I don't think
         // SimpleArrayElementIterator does.
         if (_wsm->hasObj()) {
@@ -89,7 +88,7 @@ public:
         return new SingleElementElementIterator(BSONElement());
     }
 
-    virtual void releaseIterator(ElementIterator* iterator) const {
+    void releaseIterator(ElementIterator* iterator) const final {
         delete iterator;
     }
 
@@ -106,7 +105,7 @@ public:
         return _key;
     }
 
-    virtual ElementIterator* allocateIterator(const ElementPath* path) const {
+    ElementIterator* allocateIterator(const ElementPath* path) const final {
         BSONObjIterator keyPatternIt(_keyPattern);
         BSONObjIterator keyDataIt(_key);
 
@@ -132,7 +131,7 @@ public:
         return new SingleElementElementIterator(BSONElement());
     }
 
-    virtual void releaseIterator(ElementIterator* iterator) const {
+    void releaseIterator(ElementIterator* iterator) const final {
         delete iterator;
     }
 
diff --git a/src/mongo/db/exec/geo_near.cpp b/src/mongo/db/exec/geo_near.cpp
index a91b7e49583..db8f8daaa82 100644
--- a/src/mongo/db/exec/geo_near.cpp
+++ b/src/mongo/db/exec/geo_near.cpp
@@ -459,13 +459,11 @@ public:
         initPath(twoDPath);
     }
 
-    virtual ~TwoDPtInAnnulusExpression() {}
-
-    virtual void toBSON(BSONObjBuilder* out) const {
+    void toBSON(BSONObjBuilder* out) const final {
         out->append("TwoDPtInAnnulusExpression", true);
     }
 
-    virtual bool matchesSingleElement(const BSONElement& e) const {
+    bool matchesSingleElement(const BSONElement& e) const final {
         if (!e.isABSONObj())
             return false;
 
@@ -480,16 +478,16 @@ public:
     // These won't be called.
     //
 
-    virtual void debugString(StringBuilder& debug, int level = 0) const {
+    void debugString(StringBuilder& debug, int level = 0) const final {
         invariant(false);
     }
 
-    virtual bool equivalent(const MatchExpression* other) const {
+    bool equivalent(const MatchExpression* other) const final {
         invariant(false);
         return false;
     }
 
-    virtual unique_ptr<MatchExpression> shallowClone() const {
+    unique_ptr<MatchExpression> shallowClone() const final {
         invariant(false);
         return NULL;
     }
@@ -499,7 +497,7 @@ private:
 };
 
 // Helper class to maintain ownership of a match expression alongside an index scan
-class FetchStageWithMatch : public FetchStage {
+class FetchStageWithMatch final : public FetchStage {
 public:
     FetchStageWithMatch(OperationContext* txn,
                         WorkingSet* ws,
@@ -508,8 +506,6 @@ public:
                         const Collection* collection)
         : FetchStage(txn, ws, child, filter, collection), _matcher(filter) {}
 
-    virtual ~FetchStageWithMatch() {}
-
 private:
     // Owns matcher
     const unique_ptr<MatchExpression> _matcher;
diff --git a/src/mongo/db/exec/geo_near.h b/src/mongo/db/exec/geo_near.h
index e429a742197..0bfcdb02090 100644
--- a/src/mongo/db/exec/geo_near.h
+++ b/src/mongo/db/exec/geo_near.h
@@ -63,7 +63,7 @@ struct GeoNearParams {
 /**
  * Implementation of GeoNear on top of a 2D index
  */
-class GeoNear2DStage : public NearStage {
+class GeoNear2DStage final : public NearStage {
 public:
     GeoNear2DStage(const GeoNearParams& nearParams,
                    OperationContext* txn,
@@ -72,16 +72,16 @@ public:
                    IndexDescriptor* twoDIndex);
 
 protected:
-    virtual StatusWith<CoveredInterval*> nextInterval(OperationContext* txn,
-                                                      WorkingSet* workingSet,
-                                                      Collection* collection);
+    StatusWith<CoveredInterval*> nextInterval(OperationContext* txn,
+                                              WorkingSet* workingSet,
+                                              Collection* collection) final;
 
-    virtual StatusWith<double> computeDistance(WorkingSetMember* member);
+    StatusWith<double> computeDistance(WorkingSetMember* member) final;
 
-    virtual PlanStage::StageState initialize(OperationContext* txn,
-                                             WorkingSet* workingSet,
-                                             Collection* collection,
-                                             WorkingSetID* out);
+    PlanStage::StageState initialize(OperationContext* txn,
+                                     WorkingSet* workingSet,
+                                     Collection* collection,
+                                     WorkingSetID* out) final;
 
 private:
     const GeoNearParams _nearParams;
@@ -109,7 +109,7 @@ private:
 /**
  * Implementation of GeoNear on top of a 2DSphere (S2) index
  */
-class GeoNear2DSphereStage : public NearStage {
+class GeoNear2DSphereStage final : public NearStage {
 public:
     GeoNear2DSphereStage(const GeoNearParams& nearParams,
                          OperationContext* txn,
@@ -117,19 +117,19 @@ public:
                          Collection* collection,
                          IndexDescriptor* s2Index);
 
-    virtual ~GeoNear2DSphereStage();
+    ~GeoNear2DSphereStage();
 
 protected:
-    virtual StatusWith<CoveredInterval*> nextInterval(OperationContext* txn,
-                                                      WorkingSet* workingSet,
-                                                      Collection* collection);
+    StatusWith<CoveredInterval*> nextInterval(OperationContext* txn,
+                                              WorkingSet* workingSet,
+                                              Collection* collection) final;
 
-    virtual StatusWith<double> computeDistance(WorkingSetMember* member);
+    StatusWith<double> computeDistance(WorkingSetMember* member) final;
 
-    virtual PlanStage::StageState initialize(OperationContext* txn,
-                                             WorkingSet* workingSet,
-                                             Collection* collection,
-                                             WorkingSetID* out);
+    PlanStage::StageState initialize(OperationContext* txn,
+                                     WorkingSet* workingSet,
+                                     Collection* collection,
+                                     WorkingSetID* out) final;
 
 private:
     const GeoNearParams _nearParams;
diff --git a/src/mongo/db/exec/group.h b/src/mongo/db/exec/group.h
index 97fb39d27e7..ce969c9335f 100644
--- a/src/mongo/db/exec/group.h
+++ b/src/mongo/db/exec/group.h
@@ -78,7 +78,7 @@ struct GroupRequest {
  *
  * Only created through the getExecutorGroup path.
  */
-class GroupStage : public PlanStage {
+class GroupStage final : public PlanStage {
     MONGO_DISALLOW_COPYING(GroupStage);
 
 public:
@@ -86,19 +86,18 @@ public:
                const GroupRequest& request,
                WorkingSet* workingSet,
                PlanStage* child);
-    virtual ~GroupStage() {}
 
-    virtual StageState work(WorkingSetID* out);
-    virtual bool isEOF();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    StageState work(WorkingSetID* out) final;
+    bool isEOF() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_GROUP;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/idhack.h b/src/mongo/db/exec/idhack.h
index 19b12cbbc09..71f783431a1 100644
--- a/src/mongo/db/exec/idhack.h
+++ b/src/mongo/db/exec/idhack.h
@@ -43,7 +43,7 @@ class RecordCursor;
  * A standalone stage implementing the fast path for key-value retrievals
  * via the _id index.
  */
-class IDHackStage : public PlanStage {
+class IDHackStage final : public PlanStage {
 public:
     /** Takes ownership of all the arguments -collection. */
     IDHackStage(OperationContext* txn,
@@ -53,29 +53,29 @@ public:
 
     IDHackStage(OperationContext* txn, Collection* collection, const BSONObj& key, WorkingSet* ws);
 
-    virtual ~IDHackStage();
+    ~IDHackStage();
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doSaveState();
-    virtual void doRestoreState();
-    virtual void doDetachFromOperationContext();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doSaveState() final;
+    void doRestoreState() final;
+    void doDetachFromOperationContext() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
     /**
      * ID Hack has a very strict criteria for the queries it supports.
      */
     static bool supportsQuery(const CanonicalQuery& query);
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_IDHACK;
     }
 
     std::unique_ptr<PlanStageStats> getStats();
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/index_scan.h b/src/mongo/db/exec/index_scan.h
index 5ae2319800c..aae3d54ec4c 100644
--- a/src/mongo/db/exec/index_scan.h
+++ b/src/mongo/db/exec/index_scan.h
@@ -70,7 +70,7 @@ struct IndexScanParams {
  *
  * Sub-stage preconditions: None.  Is a leaf and consumes no stage data.
  */
-class IndexScan : public PlanStage {
+class IndexScan final : public PlanStage {
 public:
     /**
      * Keeps track of what this index scan is currently doing so that it
@@ -95,23 +95,21 @@ public:
               WorkingSet* workingSet,
               const MatchExpression* filter);
 
-    virtual ~IndexScan() {}
+    StageState work(WorkingSetID* out) final;
+    bool isEOF() final;
+    void doSaveState() final;
+    void doRestoreState() final;
+    void doDetachFromOperationContext() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageState work(WorkingSetID* out);
-    virtual bool isEOF();
-    virtual void doSaveState();
-    virtual void doRestoreState();
-    virtual void doDetachFromOperationContext();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
-
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_IXSCAN;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/keep_mutations.h b/src/mongo/db/exec/keep_mutations.h
index d76ba32dac8..67ff15afca1 100644
--- a/src/mongo/db/exec/keep_mutations.h
+++ b/src/mongo/db/exec/keep_mutations.h
@@ -44,21 +44,21 @@ namespace mongo {
  * results when possible.  The query planner is responsible for determining when it's valid to
  * merge these results.
  */
-class KeepMutationsStage : public PlanStage {
+class KeepMutationsStage final : public PlanStage {
 public:
     KeepMutationsStage(const MatchExpression* filter, WorkingSet* ws, PlanStage* child);
-    virtual ~KeepMutationsStage();
+    ~KeepMutationsStage();
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_KEEP_MUTATIONS;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/limit.h b/src/mongo/db/exec/limit.h
index 33af499d5f8..de8d1ae2598 100644
--- a/src/mongo/db/exec/limit.h
+++ b/src/mongo/db/exec/limit.h
@@ -42,21 +42,21 @@ namespace mongo {
  *
  * Preconditions: None.
  */
-class LimitStage : public PlanStage {
+class LimitStage final : public PlanStage {
 public:
     LimitStage(long long limit, WorkingSet* ws, PlanStage* child);
-    virtual ~LimitStage();
+    ~LimitStage();
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_LIMIT;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/merge_sort.h b/src/mongo/db/exec/merge_sort.h
index 51114bbd0ca..ed9fd2f2a11 100644
--- a/src/mongo/db/exec/merge_sort.h
+++ b/src/mongo/db/exec/merge_sort.h
@@ -53,7 +53,7 @@ class MergeSortStageParams;
  * Preconditions: For each field in 'pattern' all inputs in the child must handle a
  * getFieldDotted for that field.
  */
-class MergeSortStage : public PlanStage {
+class MergeSortStage final : public PlanStage {
 public:
     MergeSortStage(const MergeSortStageParams& params,
                    WorkingSet* ws,
@@ -61,18 +61,18 @@ public:
 
     void addChild(PlanStage* child);
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_SORT_MERGE;
     }
 
     std::unique_ptr<PlanStageStats> getStats();
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/multi_iterator.h b/src/mongo/db/exec/multi_iterator.h
index 9bcbdb3c1c1..9d67d29abaa 100644
--- a/src/mongo/db/exec/multi_iterator.h
+++ b/src/mongo/db/exec/multi_iterator.h
@@ -45,36 +45,34 @@ namespace mongo {
  * special commands that work with RecordCursors. For example, it is used by the
  * parallelCollectionScan and repairCursor commands
  */
-class MultiIteratorStage : public PlanStage {
+class MultiIteratorStage final : public PlanStage {
 public:
     MultiIteratorStage(OperationContext* txn, WorkingSet* ws, Collection* collection);
 
-    ~MultiIteratorStage() {}
-
     void addIterator(std::unique_ptr<RecordCursor> it);
 
-    virtual PlanStage::StageState work(WorkingSetID* out);
+    PlanStage::StageState work(WorkingSetID* out) final;
 
-    virtual bool isEOF();
+    bool isEOF() final;
 
     void kill();
 
-    virtual void doSaveState();
-    virtual void doRestoreState();
-    virtual void doDetachFromOperationContext();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doSaveState() final;
+    void doRestoreState() final;
+    void doDetachFromOperationContext() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
     // Returns empty PlanStageStats object
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
     // Not used.
-    virtual SpecificStats* getSpecificStats() const {
+    SpecificStats* getSpecificStats() const final {
         return NULL;
     }
 
     // Not used.
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_MULTI_ITERATOR;
     }
 
diff --git a/src/mongo/db/exec/multi_plan.h b/src/mongo/db/exec/multi_plan.h
index 30b5f5f9bbf..85cc3191d13 100644
--- a/src/mongo/db/exec/multi_plan.h
+++ b/src/mongo/db/exec/multi_plan.h
@@ -49,7 +49,7 @@ namespace mongo {
  *
  * Owns the query solutions and PlanStage roots for all candidate plans.
  */
-class MultiPlanStage : public PlanStage {
+class MultiPlanStage final : public PlanStage {
 public:
     /**
      * Takes no ownership.
@@ -62,22 +62,22 @@ public:
                    CanonicalQuery* cq,
                    bool shouldCache = true);
 
-    virtual bool isEOF();
+    bool isEOF() final;
 
-    virtual StageState work(WorkingSetID* out);
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_MULTI_PLAN;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     /**
      * Takes ownership of QuerySolution and PlanStage. not of WorkingSet
diff --git a/src/mongo/db/exec/near.h b/src/mongo/db/exec/near.h
index 20603cc5e50..1a10d9143da 100644
--- a/src/mongo/db/exec/near.h
+++ b/src/mongo/db/exec/near.h
@@ -87,17 +87,17 @@ class NearStage : public PlanStage {
 public:
     struct CoveredInterval;
 
-    virtual ~NearStage();
+    ~NearStage();
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doReattachToOperationContext(OperationContext* opCtx) final;
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const;
-    virtual std::unique_ptr<PlanStageStats> getStats();
-    virtual const SpecificStats* getSpecificStats() const;
+    StageType stageType() const final;
+    std::unique_ptr<PlanStageStats> getStats() final;
+    const SpecificStats* getSpecificStats() const final;
 
 protected:
     /**
diff --git a/src/mongo/db/exec/oplogstart.h b/src/mongo/db/exec/oplogstart.h
index 14db9e9b585..033f51a8c9d 100644
--- a/src/mongo/db/exec/oplogstart.h
+++ b/src/mongo/db/exec/oplogstart.h
@@ -58,7 +58,7 @@ namespace mongo {
  * Why is this a stage?  Because we want to yield, and we want to be notified of RecordId
  * invalidations.  :(
  */
-class OplogStart : public PlanStage {
+class OplogStart final : public PlanStage {
 public:
     // Does not take ownership.
     OplogStart(OperationContext* txn,
@@ -66,27 +66,27 @@ public:
                MatchExpression* filter,
                WorkingSet* ws);
 
-    virtual StageState work(WorkingSetID* out);
-    virtual bool isEOF();
+    StageState work(WorkingSetID* out) final;
+    bool isEOF() final;
 
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
-    virtual void doSaveState();
-    virtual void doRestoreState();
-    virtual void doDetachFromOperationContext();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
+    void doSaveState() final;
+    void doRestoreState() final;
+    void doDetachFromOperationContext() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
     // Returns empty PlanStageStats object
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
     //
     // Exec stats -- do not call for the oplog start stage.
     //
 
-    virtual const SpecificStats* getSpecificStats() const {
+    const SpecificStats* getSpecificStats() const final {
         return NULL;
     }
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_OPLOG_START;
     }
 
diff --git a/src/mongo/db/exec/or.h b/src/mongo/db/exec/or.h
index 7a10a78ae7d..d0fd1a33209 100644
--- a/src/mongo/db/exec/or.h
+++ b/src/mongo/db/exec/or.h
@@ -43,25 +43,25 @@ namespace mongo {
  *
  * If we're deduping, we may fail to dedup any invalidated RecordId properly.
  */
-class OrStage : public PlanStage {
+class OrStage final : public PlanStage {
 public:
     OrStage(WorkingSet* ws, bool dedup, const MatchExpression* filter);
 
     void addChild(PlanStage* child);
 
-    virtual bool isEOF();
+    bool isEOF() final;
 
-    virtual StageState work(WorkingSetID* out);
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_OR;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/pipeline_proxy.h b/src/mongo/db/exec/pipeline_proxy.h
index 84f1a867f2e..a67d993d4a3 100644
--- a/src/mongo/db/exec/pipeline_proxy.h
+++ b/src/mongo/db/exec/pipeline_proxy.h
@@ -42,23 +42,23 @@ namespace mongo {
 /**
  * Stage for pulling results out from an aggregation pipeline.
  */
-class PipelineProxyStage : public PlanStage {
+class PipelineProxyStage final : public PlanStage {
 public:
     PipelineProxyStage(boost::intrusive_ptr<Pipeline> pipeline,
                        const std::shared_ptr<PlanExecutor>& child,
                        WorkingSet* ws);
 
-    virtual PlanStage::StageState work(WorkingSetID* out);
+    PlanStage::StageState work(WorkingSetID* out) final;
 
-    virtual bool isEOF();
+    bool isEOF() final;
 
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
     //
     // Manage our OperationContext.
     //
-    virtual void doDetachFromOperationContext();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    void doDetachFromOperationContext() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
     /**
      * Make obj the next object returned by getNext().
@@ -72,16 +72,16 @@ public:
     std::shared_ptr<PlanExecutor> getChildExecutor();
 
     // Returns empty PlanStageStats object
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
 
     // Not used.
-    virtual SpecificStats* getSpecificStats() const {
+    SpecificStats* getSpecificStats() const final {
         return NULL;
     }
 
     // Not used.
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_PIPELINE_PROXY;
     }
 
diff --git a/src/mongo/db/exec/plan_stats.h b/src/mongo/db/exec/plan_stats.h
index 82f8cbc7e10..67e3250d8ec 100644
--- a/src/mongo/db/exec/plan_stats.h
+++ b/src/mongo/db/exec/plan_stats.h
@@ -146,9 +146,7 @@ private:
 struct AndHashStats : public SpecificStats {
     AndHashStats() : flaggedButPassed(0), flaggedInProgress(0), memUsage(0), memLimit(0) {}
 
-    virtual ~AndHashStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         AndHashStats* specific = new AndHashStats(*this);
         return specific;
     }
@@ -178,9 +176,7 @@ struct AndHashStats : public SpecificStats {
 struct AndSortedStats : public SpecificStats {
     AndSortedStats() : flagged(0) {}
 
-    virtual ~AndSortedStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         AndSortedStats* specific = new AndSortedStats(*this);
         return specific;
     }
@@ -195,7 +191,7 @@ struct AndSortedStats : public SpecificStats {
 struct CachedPlanStats : public SpecificStats {
     CachedPlanStats() {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         return new CachedPlanStats(*this);
     }
 };
@@ -203,7 +199,7 @@ struct CachedPlanStats : public SpecificStats {
 struct CollectionScanStats : public SpecificStats {
     CollectionScanStats() : docsTested(0), direction(1) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         CollectionScanStats* specific = new CollectionScanStats(*this);
         return specific;
     }
@@ -219,7 +215,7 @@ struct CollectionScanStats : public SpecificStats {
 struct CountStats : public SpecificStats {
     CountStats() : nCounted(0), nSkipped(0), trivialCount(false) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         CountStats* specific = new CountStats(*this);
         return specific;
     }
@@ -244,9 +240,7 @@ struct CountScanStats : public SpecificStats {
           isUnique(false),
           keysExamined(0) {}
 
-    virtual ~CountScanStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         CountScanStats* specific = new CountScanStats(*this);
         // BSON objects have to be explicitly copied.
         specific->keyPattern = keyPattern.getOwned();
@@ -270,7 +264,7 @@ struct CountScanStats : public SpecificStats {
 struct DeleteStats : public SpecificStats {
     DeleteStats() : docsDeleted(0), nInvalidateSkips(0) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         return new DeleteStats(*this);
     }
 
@@ -284,7 +278,7 @@ struct DeleteStats : public SpecificStats {
 struct DistinctScanStats : public SpecificStats {
     DistinctScanStats() : keysExamined(0), indexVersion(0) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         DistinctScanStats* specific = new DistinctScanStats(*this);
         specific->keyPattern = keyPattern.getOwned();
         return specific;
@@ -303,9 +297,7 @@ struct DistinctScanStats : public SpecificStats {
 struct FetchStats : public SpecificStats {
     FetchStats() : alreadyHasObj(0), forcedFetches(0), docsExamined(0) {}
 
-    virtual ~FetchStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         FetchStats* specific = new FetchStats(*this);
         return specific;
     }
@@ -323,9 +315,7 @@ struct FetchStats : public SpecificStats {
 struct GroupStats : public SpecificStats {
     GroupStats() : nGroups(0) {}
 
-    virtual ~GroupStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         GroupStats* specific = new GroupStats(*this);
         return specific;
     }
@@ -337,9 +327,7 @@ struct GroupStats : public SpecificStats {
 struct IDHackStats : public SpecificStats {
     IDHackStats() : keysExamined(0), docsExamined(0) {}
 
-    virtual ~IDHackStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         IDHackStats* specific = new IDHackStats(*this);
         return specific;
     }
@@ -364,9 +352,7 @@ struct IndexScanStats : public SpecificStats {
           seenInvalidated(0),
           keysExamined(0) {}
 
-    virtual ~IndexScanStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         IndexScanStats* specific = new IndexScanStats(*this);
         // BSON objects have to be explicitly copied.
         specific->keyPattern = keyPattern.getOwned();
@@ -412,7 +398,7 @@ struct IndexScanStats : public SpecificStats {
 struct LimitStats : public SpecificStats {
     LimitStats() : limit(0) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         LimitStats* specific = new LimitStats(*this);
         return specific;
     }
@@ -423,7 +409,7 @@ struct LimitStats : public SpecificStats {
 struct MockStats : public SpecificStats {
     MockStats() {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         return new MockStats(*this);
     }
 };
@@ -431,7 +417,7 @@ struct MockStats : public SpecificStats {
 struct MultiPlanStats : public SpecificStats {
     MultiPlanStats() {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         return new MultiPlanStats(*this);
     }
 };
@@ -439,9 +425,7 @@ struct MultiPlanStats : public SpecificStats {
 struct OrStats : public SpecificStats {
     OrStats() : dupsTested(0), dupsDropped(0), locsForgotten(0) {}
 
-    virtual ~OrStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         OrStats* specific = new OrStats(*this);
         return specific;
     }
@@ -456,7 +440,7 @@ struct OrStats : public SpecificStats {
 struct ProjectionStats : public SpecificStats {
     ProjectionStats() {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         ProjectionStats* specific = new ProjectionStats(*this);
         return specific;
     }
@@ -468,9 +452,7 @@ struct ProjectionStats : public SpecificStats {
 struct SortStats : public SpecificStats {
     SortStats() : forcedFetches(0), memUsage(0), memLimit(0) {}
 
-    virtual ~SortStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         SortStats* specific = new SortStats(*this);
         return specific;
     }
@@ -494,9 +476,7 @@ struct SortStats : public SpecificStats {
 struct MergeSortStats : public SpecificStats {
     MergeSortStats() : dupsTested(0), dupsDropped(0), forcedFetches(0) {}
 
-    virtual ~MergeSortStats() {}
-
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         MergeSortStats* specific = new MergeSortStats(*this);
         return specific;
     }
@@ -514,7 +494,7 @@ struct MergeSortStats : public SpecificStats {
 struct ShardingFilterStats : public SpecificStats {
     ShardingFilterStats() : chunkSkips(0) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         ShardingFilterStats* specific = new ShardingFilterStats(*this);
         return specific;
     }
@@ -525,7 +505,7 @@ struct ShardingFilterStats : public SpecificStats {
 struct SkipStats : public SpecificStats {
     SkipStats() : skip(0) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         SkipStats* specific = new SkipStats(*this);
         return specific;
     }
@@ -562,7 +542,7 @@ class NearStats : public SpecificStats {
 public:
     NearStats() {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         return new NearStats(*this);
     }
 
@@ -591,7 +571,7 @@ struct UpdateStats : public SpecificStats {
           inserted(false),
           nInvalidateSkips(0) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         return new UpdateStats(*this);
     }
 
@@ -629,7 +609,7 @@ struct UpdateStats : public SpecificStats {
 struct TextStats : public SpecificStats {
     TextStats() : parsedTextQuery() {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         TextStats* specific = new TextStats(*this);
         return specific;
     }
@@ -646,7 +626,7 @@ struct TextStats : public SpecificStats {
 struct TextMatchStats : public SpecificStats {
     TextMatchStats() : docsRejected(0) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         TextMatchStats* specific = new TextMatchStats(*this);
         return specific;
     }
@@ -657,7 +637,7 @@ struct TextMatchStats : public SpecificStats {
 struct TextOrStats : public SpecificStats {
     TextOrStats() : fetches(0) {}
 
-    virtual SpecificStats* clone() const {
+    SpecificStats* clone() const final {
         TextOrStats* specific = new TextOrStats(*this);
         return specific;
     }
diff --git a/src/mongo/db/exec/projection.h b/src/mongo/db/exec/projection.h
index 7fa5f0fcc2d..58588b3c1dc 100644
--- a/src/mongo/db/exec/projection.h
+++ b/src/mongo/db/exec/projection.h
@@ -73,20 +73,20 @@ struct ProjectionStageParams {
 /**
  * This stage computes a projection.
  */
-class ProjectionStage : public PlanStage {
+class ProjectionStage final : public PlanStage {
 public:
     ProjectionStage(const ProjectionStageParams& params, WorkingSet* ws, PlanStage* child);
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_PROJECTION;
     }
 
     std::unique_ptr<PlanStageStats> getStats();
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     typedef unordered_set<StringData, StringData::Hasher> FieldSet;
 
diff --git a/src/mongo/db/exec/queued_data_stage.h b/src/mongo/db/exec/queued_data_stage.h
index cceaaf10457..a3e57f6101f 100644
--- a/src/mongo/db/exec/queued_data_stage.h
+++ b/src/mongo/db/exec/queued_data_stage.h
@@ -45,15 +45,15 @@ class RecordId;
  * queue.  Calls to QueuedDataStage::work() pop values off that queue and return them in FIFO
  * order, annotating the working set with data when appropriate.
  */
-class QueuedDataStage : public PlanStage {
+class QueuedDataStage final : public PlanStage {
 public:
     QueuedDataStage(WorkingSet* ws);
 
-    virtual StageState work(WorkingSetID* out);
+    StageState work(WorkingSetID* out) final;
 
-    virtual bool isEOF();
+    bool isEOF() final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_QUEUED_DATA;
     }
 
@@ -61,9 +61,9 @@ public:
     // Exec stats
     //
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     /**
      * Add a result to the back of the queue.
diff --git a/src/mongo/db/exec/shard_filter.h b/src/mongo/db/exec/shard_filter.h
index be3f98d526b..393cdbe8975 100644
--- a/src/mongo/db/exec/shard_filter.h
+++ b/src/mongo/db/exec/shard_filter.h
@@ -69,23 +69,23 @@ class CollectionMetadata;
  * Preconditions: Child must be fetched.  TODO: when covering analysis is in just build doc
  * and check that against shard key.  See SERVER-5022.
  */
-class ShardFilterStage : public PlanStage {
+class ShardFilterStage final : public PlanStage {
 public:
     ShardFilterStage(const std::shared_ptr<CollectionMetadata>& metadata,
                      WorkingSet* ws,
                      PlanStage* child);
-    virtual ~ShardFilterStage();
+    ~ShardFilterStage();
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_SHARDING_FILTER;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/skip.h b/src/mongo/db/exec/skip.h
index 3d2b165abd8..45e01bbd120 100644
--- a/src/mongo/db/exec/skip.h
+++ b/src/mongo/db/exec/skip.h
@@ -41,21 +41,21 @@ namespace mongo {
  *
  * Preconditions: None.
  */
-class SkipStage : public PlanStage {
+class SkipStage final : public PlanStage {
 public:
     SkipStage(long long toSkip, WorkingSet* ws, PlanStage* child);
-    virtual ~SkipStage();
+    ~SkipStage();
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_SKIP;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/sort.h b/src/mongo/db/exec/sort.h
index 39a32ba9c88..f0a29b84efc 100644
--- a/src/mongo/db/exec/sort.h
+++ b/src/mongo/db/exec/sort.h
@@ -139,23 +139,23 @@ private:
  * Preconditions: For each field in 'pattern', all inputs in the child must handle a
  * getFieldDotted for that field.
  */
-class SortStage : public PlanStage {
+class SortStage final : public PlanStage {
 public:
     SortStage(const SortStageParams& params, WorkingSet* ws, PlanStage* child);
-    virtual ~SortStage();
+    ~SortStage();
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
+    void doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_SORT;
     }
 
     std::unique_ptr<PlanStageStats> getStats();
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/subplan.h b/src/mongo/db/exec/subplan.h
index f85ce59b542..47b54eea46f 100644
--- a/src/mongo/db/exec/subplan.h
+++ b/src/mongo/db/exec/subplan.h
@@ -64,7 +64,7 @@ class OperationContext;
  *
  *   --Plans for entire rooted $or queries are neither written to nor read from the plan cache.
  */
-class SubplanStage : public PlanStage {
+class SubplanStage final : public PlanStage {
 public:
     SubplanStage(OperationContext* txn,
                  Collection* collection,
@@ -74,18 +74,18 @@ public:
 
     static bool canUseSubplanning(const CanonicalQuery& query);
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_SUBPLAN;
     }
 
     std::unique_ptr<PlanStageStats> getStats();
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/text.h b/src/mongo/db/exec/text.h
index 4d0d57f66d0..e0636422eff 100644
--- a/src/mongo/db/exec/text.h
+++ b/src/mongo/db/exec/text.h
@@ -69,7 +69,7 @@ struct TextStageParams {
  *
  * Output type: LOC_AND_OBJ.
  */
-class TextStage : public PlanStage {
+class TextStage final : public PlanStage {
 public:
     TextStage(OperationContext* txn,
               const TextStageParams& params,
diff --git a/src/mongo/db/exec/text_match.h b/src/mongo/db/exec/text_match.h
index cacec80c4e6..df3e3b9ae68 100644
--- a/src/mongo/db/exec/text_match.h
+++ b/src/mongo/db/exec/text_match.h
@@ -61,7 +61,7 @@ public:
                    const FTSQuery& query,
                    const FTSSpec& spec,
                    WorkingSet* ws);
-    ~TextMatchStage() final;
+    ~TextMatchStage();
 
     void addChild(PlanStage* child);
 
diff --git a/src/mongo/db/exec/text_or.cpp b/src/mongo/db/exec/text_or.cpp
index 41c57530a19..bbdbabdd4d0 100644
--- a/src/mongo/db/exec/text_or.cpp
+++ b/src/mongo/db/exec/text_or.cpp
@@ -297,7 +297,7 @@ public:
         return getObj();
     }
 
-    virtual ElementIterator* allocateIterator(const ElementPath* path) const {
+    ElementIterator* allocateIterator(const ElementPath* path) const final {
         WorkingSetMember* member = _ws->get(_id);
         if (!member->hasObj()) {
             // Try to look in the key.
@@ -323,7 +323,7 @@ public:
         return new BSONElementIterator(path, getObj());
     }
 
-    virtual void releaseIterator(ElementIterator* iterator) const {
+    void releaseIterator(ElementIterator* iterator) const final {
         delete iterator;
     }
 
diff --git a/src/mongo/db/exec/text_or.h b/src/mongo/db/exec/text_or.h
index c2018bda166..5d9df26f439 100644
--- a/src/mongo/db/exec/text_or.h
+++ b/src/mongo/db/exec/text_or.h
@@ -78,7 +78,7 @@ public:
                 WorkingSet* ws,
                 const MatchExpression* filter,
                 IndexDescriptor* index);
-    ~TextOrStage() final;
+    ~TextOrStage();
 
     void addChild(unique_ptr<PlanStage> child);
 
diff --git a/src/mongo/db/exec/update.h b/src/mongo/db/exec/update.h
index c728bda5392..87859c9ff5f 100644
--- a/src/mongo/db/exec/update.h
+++ b/src/mongo/db/exec/update.h
@@ -71,7 +71,7 @@ private:
  *
  * Callers of work() must be holding a write lock.
  */
-class UpdateStage : public PlanStage {
+class UpdateStage final : public PlanStage {
     MONGO_DISALLOW_COPYING(UpdateStage);
 
 public:
@@ -81,19 +81,19 @@ public:
                 Collection* collection,
                 PlanStage* child);
 
-    virtual bool isEOF();
-    virtual StageState work(WorkingSetID* out);
+    bool isEOF() final;
+    StageState work(WorkingSetID* out) final;
 
-    virtual void doRestoreState();
-    virtual void doReattachToOperationContext(OperationContext* opCtx);
+    void doRestoreState() final;
+    void doReattachToOperationContext(OperationContext* opCtx) final;
 
-    virtual StageType stageType() const {
+    StageType stageType() const final {
         return STAGE_UPDATE;
     }
 
-    virtual std::unique_ptr<PlanStageStats> getStats();
+    std::unique_ptr<PlanStageStats> getStats() final;
 
-    virtual const SpecificStats* getSpecificStats() const;
+    const SpecificStats* getSpecificStats() const final;
 
     static const char* kStageType;
 
diff --git a/src/mongo/db/exec/working_set_computed_data.h b/src/mongo/db/exec/working_set_computed_data.h
index c7dc27ce45d..9c948e7912b 100644
--- a/src/mongo/db/exec/working_set_computed_data.h
+++ b/src/mongo/db/exec/working_set_computed_data.h
@@ -41,7 +41,7 @@ public:
         return _score;
     }
 
-    virtual TextScoreComputedData* clone() const {
+    TextScoreComputedData* clone() const final {
         return new TextScoreComputedData(_score);
     }
 
@@ -58,7 +58,7 @@ public:
         return _dist;
     }
 
-    virtual GeoDistanceComputedData* clone() const {
+    GeoDistanceComputedData* clone() const final {
         return new GeoDistanceComputedData(_dist);
     }
 
@@ -75,7 +75,7 @@ public:
         return _key;
     }
 
-    virtual IndexKeyComputedData* clone() const {
+    IndexKeyComputedData* clone() const final {
         return new IndexKeyComputedData(_key);
     }
 
@@ -92,7 +92,7 @@ public:
         return _point;
     }
 
-    virtual GeoNearPointComputedData* clone() const {
+    GeoNearPointComputedData* clone() const final {
         return new GeoNearPointComputedData(_point);
     }