SERVER-17633 add const qualifiers to PlanStage and Explain interfaces

60 files changed, 129 insertions, 130 deletions

diff --git a/src/mongo/db/exec/and_hash.cpp b/src/mongo/db/exec/and_hash.cpp
index 4a11db9862c..64bac7b3c66 100644
--- a/src/mongo/db/exec/and_hash.cpp
+++ b/src/mongo/db/exec/and_hash.cpp
@@ -543,11 +543,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* AndHashStage::getCommonStats() {
+    const CommonStats* AndHashStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* AndHashStage::getSpecificStats() {
+    const SpecificStats* AndHashStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/and_hash.h b/src/mongo/db/exec/and_hash.h
index 7a9eb3228f3..1fe60234c85 100644
--- a/src/mongo/db/exec/and_hash.h
+++ b/src/mongo/db/exec/and_hash.h
@@ -87,9 +87,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/and_sorted.cpp b/src/mongo/db/exec/and_sorted.cpp
index e0e0a664806..91036304f58 100644
--- a/src/mongo/db/exec/and_sorted.cpp
+++ b/src/mongo/db/exec/and_sorted.cpp
@@ -339,11 +339,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* AndSortedStage::getCommonStats() {
+    const CommonStats* AndSortedStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* AndSortedStage::getSpecificStats() {
+    const SpecificStats* AndSortedStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/and_sorted.h b/src/mongo/db/exec/and_sorted.h
index b6c3a9ed10e..dc57f80afcd 100644
--- a/src/mongo/db/exec/and_sorted.h
+++ b/src/mongo/db/exec/and_sorted.h
@@ -71,9 +71,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/cached_plan.cpp b/src/mongo/db/exec/cached_plan.cpp
index a8d2d1d592b..7e3fed36a98 100644
--- a/src/mongo/db/exec/cached_plan.cpp
+++ b/src/mongo/db/exec/cached_plan.cpp
@@ -348,11 +348,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* CachedPlanStage::getCommonStats() {
+    const CommonStats* CachedPlanStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* CachedPlanStage::getSpecificStats() {
+    const SpecificStats* CachedPlanStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/cached_plan.h b/src/mongo/db/exec/cached_plan.h
index c5d15fb7cac..ccc82d9cc7d 100644
--- a/src/mongo/db/exec/cached_plan.h
+++ b/src/mongo/db/exec/cached_plan.h
@@ -75,9 +75,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/collection_scan.cpp b/src/mongo/db/exec/collection_scan.cpp
index af7605c512b..7815ec85926 100644
--- a/src/mongo/db/exec/collection_scan.cpp
+++ b/src/mongo/db/exec/collection_scan.cpp
@@ -270,11 +270,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* CollectionScan::getCommonStats() {
+    const CommonStats* CollectionScan::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* CollectionScan::getSpecificStats() {
+    const SpecificStats* CollectionScan::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/collection_scan.h b/src/mongo/db/exec/collection_scan.h
index 375e4ad8fde..939b293b209 100644
--- a/src/mongo/db/exec/collection_scan.h
+++ b/src/mongo/db/exec/collection_scan.h
@@ -67,9 +67,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/count.cpp b/src/mongo/db/exec/count.cpp
index 512ae52a2e2..5fbcc28a40b 100644
--- a/src/mongo/db/exec/count.cpp
+++ b/src/mongo/db/exec/count.cpp
@@ -209,11 +209,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* CountStage::getCommonStats() {
+    const CommonStats* CountStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* CountStage::getSpecificStats() {
+    const SpecificStats* CountStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/count.h b/src/mongo/db/exec/count.h
index 4a2954ad140..70081984d23 100644
--- a/src/mongo/db/exec/count.h
+++ b/src/mongo/db/exec/count.h
@@ -98,9 +98,9 @@ namespace mongo {
 
         PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/count_scan.cpp b/src/mongo/db/exec/count_scan.cpp
index 5ab657704f3..1a801c82566 100644
--- a/src/mongo/db/exec/count_scan.cpp
+++ b/src/mongo/db/exec/count_scan.cpp
@@ -168,11 +168,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* CountScan::getCommonStats() {
+    const CommonStats* CountScan::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* CountScan::getSpecificStats() {
+    const SpecificStats* CountScan::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/count_scan.h b/src/mongo/db/exec/count_scan.h
index e1b3966a22e..d04b2b89e8b 100644
--- a/src/mongo/db/exec/count_scan.h
+++ b/src/mongo/db/exec/count_scan.h
@@ -82,9 +82,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/delete.cpp b/src/mongo/db/exec/delete.cpp
index 678b5197acd..0a8cb0509da 100644
--- a/src/mongo/db/exec/delete.cpp
+++ b/src/mongo/db/exec/delete.cpp
@@ -296,11 +296,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* DeleteStage::getCommonStats() {
+    const CommonStats* DeleteStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* DeleteStage::getSpecificStats() {
+    const SpecificStats* DeleteStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/delete.h b/src/mongo/db/exec/delete.h
index cfd599750bf..c84d0e9bfd6 100644
--- a/src/mongo/db/exec/delete.h
+++ b/src/mongo/db/exec/delete.h
@@ -100,9 +100,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/distinct_scan.cpp b/src/mongo/db/exec/distinct_scan.cpp
index 9a38f7d675a..4185877064c 100644
--- a/src/mongo/db/exec/distinct_scan.cpp
+++ b/src/mongo/db/exec/distinct_scan.cpp
@@ -154,11 +154,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* DistinctScan::getCommonStats() {
+    const CommonStats* DistinctScan::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* DistinctScan::getSpecificStats() {
+    const SpecificStats* DistinctScan::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/distinct_scan.h b/src/mongo/db/exec/distinct_scan.h
index bfc18104cea..8d7f0a8a18b 100644
--- a/src/mongo/db/exec/distinct_scan.h
+++ b/src/mongo/db/exec/distinct_scan.h
@@ -92,9 +92,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/eof.cpp b/src/mongo/db/exec/eof.cpp
index 3b9b3528b2f..1766c9b7a3e 100644
--- a/src/mongo/db/exec/eof.cpp
+++ b/src/mongo/db/exec/eof.cpp
@@ -76,12 +76,12 @@ namespace mongo {
         return new PlanStageStats(_commonStats, STAGE_EOF);
     }
 
-    const CommonStats* EOFStage::getCommonStats() {
+    const CommonStats* EOFStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* EOFStage::getSpecificStats() {
-        return NULL;
+    const SpecificStats* EOFStage::getSpecificStats() const {
+        return nullptr;
     }
 
 }  // namespace mongo
diff --git a/src/mongo/db/exec/eof.h b/src/mongo/db/exec/eof.h
index 7d83b4e2e96..247453d1d03 100644
--- a/src/mongo/db/exec/eof.h
+++ b/src/mongo/db/exec/eof.h
@@ -55,9 +55,9 @@ namespace mongo {
 
         PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/fetch.cpp b/src/mongo/db/exec/fetch.cpp
index b98a04da01c..423ef2546c3 100644
--- a/src/mongo/db/exec/fetch.cpp
+++ b/src/mongo/db/exec/fetch.cpp
@@ -249,11 +249,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* FetchStage::getCommonStats() {
+    const CommonStats* FetchStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* FetchStage::getSpecificStats() {
+    const SpecificStats* FetchStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/fetch.h b/src/mongo/db/exec/fetch.h
index 05af024ef90..18fbeedb3db 100644
--- a/src/mongo/db/exec/fetch.h
+++ b/src/mongo/db/exec/fetch.h
@@ -68,9 +68,9 @@ namespace mongo {
 
         PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/group.cpp b/src/mongo/db/exec/group.cpp
index 85e7d613cc2..d5d3688d4c5 100644
--- a/src/mongo/db/exec/group.cpp
+++ b/src/mongo/db/exec/group.cpp
@@ -292,11 +292,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* GroupStage::getCommonStats() {
+    const CommonStats* GroupStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* GroupStage::getSpecificStats() {
+    const SpecificStats* GroupStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/group.h b/src/mongo/db/exec/group.h
index 2374fc7b2b0..dcf96570cbe 100644
--- a/src/mongo/db/exec/group.h
+++ b/src/mongo/db/exec/group.h
@@ -100,9 +100,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/idhack.cpp b/src/mongo/db/exec/idhack.cpp
index 98aeb7162ff..26de70dc7aa 100644
--- a/src/mongo/db/exec/idhack.cpp
+++ b/src/mongo/db/exec/idhack.cpp
@@ -240,11 +240,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* IDHackStage::getCommonStats() {
+    const CommonStats* IDHackStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* IDHackStage::getSpecificStats() {
+    const SpecificStats* IDHackStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/idhack.h b/src/mongo/db/exec/idhack.h
index 800cd8e4675..d1f1020342d 100644
--- a/src/mongo/db/exec/idhack.h
+++ b/src/mongo/db/exec/idhack.h
@@ -68,9 +68,9 @@ namespace mongo {
 
         PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/index_scan.cpp b/src/mongo/db/exec/index_scan.cpp
index e8f59c07496..3cf0ed093cb 100644
--- a/src/mongo/db/exec/index_scan.cpp
+++ b/src/mongo/db/exec/index_scan.cpp
@@ -308,11 +308,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* IndexScan::getCommonStats() {
+    const CommonStats* IndexScan::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* IndexScan::getSpecificStats() {
+    const SpecificStats* IndexScan::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/index_scan.h b/src/mongo/db/exec/index_scan.h
index a2cfd4bad45..0a3c1436103 100644
--- a/src/mongo/db/exec/index_scan.h
+++ b/src/mongo/db/exec/index_scan.h
@@ -114,9 +114,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/keep_mutations.cpp b/src/mongo/db/exec/keep_mutations.cpp
index a6db0eb0efd..a58c979f02a 100644
--- a/src/mongo/db/exec/keep_mutations.cpp
+++ b/src/mongo/db/exec/keep_mutations.cpp
@@ -148,11 +148,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* KeepMutationsStage::getCommonStats() {
+    const CommonStats* KeepMutationsStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* KeepMutationsStage::getSpecificStats() {
+    const SpecificStats* KeepMutationsStage::getSpecificStats() const {
         return NULL;
     }
 
diff --git a/src/mongo/db/exec/keep_mutations.h b/src/mongo/db/exec/keep_mutations.h
index 004106ba315..a4c594a1f33 100644
--- a/src/mongo/db/exec/keep_mutations.h
+++ b/src/mongo/db/exec/keep_mutations.h
@@ -63,9 +63,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/limit.cpp b/src/mongo/db/exec/limit.cpp
index 6aa83f083bc..87527e36970 100644
--- a/src/mongo/db/exec/limit.cpp
+++ b/src/mongo/db/exec/limit.cpp
@@ -121,11 +121,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* LimitStage::getCommonStats() {
+    const CommonStats* LimitStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* LimitStage::getSpecificStats() {
+    const SpecificStats* LimitStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/limit.h b/src/mongo/db/exec/limit.h
index 489eea2e589..484df742439 100644
--- a/src/mongo/db/exec/limit.h
+++ b/src/mongo/db/exec/limit.h
@@ -61,9 +61,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/merge_sort.cpp b/src/mongo/db/exec/merge_sort.cpp
index ab6e9f547e2..8fdb3ae96eb 100644
--- a/src/mongo/db/exec/merge_sort.cpp
+++ b/src/mongo/db/exec/merge_sort.cpp
@@ -278,11 +278,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* MergeSortStage::getCommonStats() {
+    const CommonStats* MergeSortStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* MergeSortStage::getSpecificStats() {
+    const SpecificStats* MergeSortStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/merge_sort.h b/src/mongo/db/exec/merge_sort.h
index 353fbaa14ec..e8e216e5fe3 100644
--- a/src/mongo/db/exec/merge_sort.h
+++ b/src/mongo/db/exec/merge_sort.h
@@ -75,9 +75,9 @@ namespace mongo {
 
         PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/multi_iterator.h b/src/mongo/db/exec/multi_iterator.h
index 453ffdfdce6..0fd88283aa7 100644
--- a/src/mongo/db/exec/multi_iterator.h
+++ b/src/mongo/db/exec/multi_iterator.h
@@ -69,8 +69,8 @@ namespace mongo {
         //
 
         virtual PlanStageStats* getStats() { return NULL; }
-        virtual CommonStats* getCommonStats() { return NULL; }
-        virtual SpecificStats* getSpecificStats() { return NULL; }
+        virtual CommonStats* getCommonStats() const { return NULL; }
+        virtual SpecificStats* getSpecificStats() const { return NULL; }
 
         virtual std::vector<PlanStage*> getChildren() const;
 
diff --git a/src/mongo/db/exec/multi_plan.cpp b/src/mongo/db/exec/multi_plan.cpp
index 3ad74d752ce..23e24a57d2c 100644
--- a/src/mongo/db/exec/multi_plan.cpp
+++ b/src/mongo/db/exec/multi_plan.cpp
@@ -508,11 +508,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* MultiPlanStage::getCommonStats() {
+    const CommonStats* MultiPlanStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* MultiPlanStage::getSpecificStats() {
+    const SpecificStats* MultiPlanStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/multi_plan.h b/src/mongo/db/exec/multi_plan.h
index 43596aea247..d820324dfe8 100644
--- a/src/mongo/db/exec/multi_plan.h
+++ b/src/mongo/db/exec/multi_plan.h
@@ -81,9 +81,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         /**
          * Takes ownership of QuerySolution and PlanStage. not of WorkingSet
diff --git a/src/mongo/db/exec/near.cpp b/src/mongo/db/exec/near.cpp
index cb1abf498a5..c3e5654b17b 100644
--- a/src/mongo/db/exec/near.cpp
+++ b/src/mongo/db/exec/near.cpp
@@ -386,11 +386,11 @@ namespace mongo {
         return _stats->stageType;
     }
 
-    const CommonStats* NearStage::getCommonStats() {
+    const CommonStats* NearStage::getCommonStats() const {
         return &_stats->common;
     }
 
-    const SpecificStats* NearStage::getSpecificStats() {
+    const SpecificStats* NearStage::getSpecificStats() const {
         return _stats->specific.get();
     }
 
diff --git a/src/mongo/db/exec/near.h b/src/mongo/db/exec/near.h
index d7d27a78331..a3db2c2b126 100644
--- a/src/mongo/db/exec/near.h
+++ b/src/mongo/db/exec/near.h
@@ -92,8 +92,8 @@ namespace mongo {
 
         virtual StageType stageType() const;
         virtual PlanStageStats* getStats();
-        virtual const CommonStats* getCommonStats();
-        virtual const SpecificStats* getSpecificStats();
+        virtual const CommonStats* getCommonStats() const;
+        virtual const SpecificStats* getSpecificStats() const;
 
     protected:
 
diff --git a/src/mongo/db/exec/oplogstart.h b/src/mongo/db/exec/oplogstart.h
index 78505a2a54c..5a52dc37489 100644
--- a/src/mongo/db/exec/oplogstart.h
+++ b/src/mongo/db/exec/oplogstart.h
@@ -83,9 +83,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats() { return NULL; }
 
-        virtual const CommonStats* getCommonStats() { return NULL; }
+        virtual const CommonStats* getCommonStats() const { return NULL; }
 
-        virtual const SpecificStats* getSpecificStats() { return NULL; }
+        virtual const SpecificStats* getSpecificStats() const { return NULL; }
 
         virtual StageType stageType() const { return STAGE_OPLOG_START; }
 
diff --git a/src/mongo/db/exec/or.cpp b/src/mongo/db/exec/or.cpp
index 8b3dd286b1b..ee57187c2a2 100644
--- a/src/mongo/db/exec/or.cpp
+++ b/src/mongo/db/exec/or.cpp
@@ -201,11 +201,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* OrStage::getCommonStats() {
+    const CommonStats* OrStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* OrStage::getSpecificStats() {
+    const SpecificStats* OrStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/or.h b/src/mongo/db/exec/or.h
index c0f92a01327..3ea2d55a466 100644
--- a/src/mongo/db/exec/or.h
+++ b/src/mongo/db/exec/or.h
@@ -64,9 +64,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/pipeline_proxy.h b/src/mongo/db/exec/pipeline_proxy.h
index 59a4d61d197..23ac96ca365 100644
--- a/src/mongo/db/exec/pipeline_proxy.h
+++ b/src/mongo/db/exec/pipeline_proxy.h
@@ -79,8 +79,8 @@ namespace mongo {
         //
 
         virtual PlanStageStats* getStats() { return NULL; }
-        virtual CommonStats* getCommonStats() { return NULL; }
-        virtual SpecificStats* getSpecificStats() { return NULL; }
+        virtual CommonStats* getCommonStats() const { return NULL; }
+        virtual SpecificStats* getSpecificStats() const { return NULL; }
 
         // Not used.
         virtual std::vector<PlanStage*> getChildren() const;
diff --git a/src/mongo/db/exec/plan_stage.h b/src/mongo/db/exec/plan_stage.h
index 98d1d80698d..07536817ca6 100644
--- a/src/mongo/db/exec/plan_stage.h
+++ b/src/mongo/db/exec/plan_stage.h
@@ -271,7 +271,7 @@ namespace mongo {
          * It must not exist past the stage. If you need the stats to outlive the stage,
          * use the getStats(...) method above.
          */
-        virtual const CommonStats* getCommonStats() = 0;
+        virtual const CommonStats* getCommonStats() const = 0;
 
         /**
          * Get stats specific to this stage. Some stages may not have specific stats, in which
@@ -281,7 +281,7 @@ namespace mongo {
          * It must not exist past the stage. If you need the stats to outlive the stage,
          * use the getStats(...) method above.
          */
-        virtual const SpecificStats* getSpecificStats() = 0;
+        virtual const SpecificStats* getSpecificStats() const = 0;
 
     };
 
diff --git a/src/mongo/db/exec/projection.cpp b/src/mongo/db/exec/projection.cpp
index e907a5eca7a..25616bfb197 100644
--- a/src/mongo/db/exec/projection.cpp
+++ b/src/mongo/db/exec/projection.cpp
@@ -285,11 +285,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* ProjectionStage::getCommonStats() {
+    const CommonStats* ProjectionStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* ProjectionStage::getSpecificStats() {
+    const SpecificStats* ProjectionStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/projection.h b/src/mongo/db/exec/projection.h
index 7724216b00e..6878861a997 100644
--- a/src/mongo/db/exec/projection.h
+++ b/src/mongo/db/exec/projection.h
@@ -95,9 +95,9 @@ namespace mongo {
 
         PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         typedef unordered_set<StringData, StringData::Hasher> FieldSet;
 
diff --git a/src/mongo/db/exec/queued_data_stage.cpp b/src/mongo/db/exec/queued_data_stage.cpp
index 1e40b87d21a..b353cb6026d 100644
--- a/src/mongo/db/exec/queued_data_stage.cpp
+++ b/src/mongo/db/exec/queued_data_stage.cpp
@@ -89,9 +89,9 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* QueuedDataStage::getCommonStats() { return &_commonStats; }
+    const CommonStats* QueuedDataStage::getCommonStats() const { return &_commonStats; }
 
-    const SpecificStats* QueuedDataStage::getSpecificStats() { return &_specificStats; }
+    const SpecificStats* QueuedDataStage::getSpecificStats() const { return &_specificStats; }
 
     void QueuedDataStage::pushBack(const PlanStage::StageState state) {
         invariant(PlanStage::ADVANCED != state);
diff --git a/src/mongo/db/exec/queued_data_stage.h b/src/mongo/db/exec/queued_data_stage.h
index b17566f1b1e..5d7a7b2b159 100644
--- a/src/mongo/db/exec/queued_data_stage.h
+++ b/src/mongo/db/exec/queued_data_stage.h
@@ -71,9 +71,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         /**
          * Add a result to the back of the queue.
diff --git a/src/mongo/db/exec/shard_filter.cpp b/src/mongo/db/exec/shard_filter.cpp
index c1aa49df04e..26f546ec836 100644
--- a/src/mongo/db/exec/shard_filter.cpp
+++ b/src/mongo/db/exec/shard_filter.cpp
@@ -156,11 +156,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* ShardFilterStage::getCommonStats() {
+    const CommonStats* ShardFilterStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* ShardFilterStage::getSpecificStats() {
+    const SpecificStats* ShardFilterStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/shard_filter.h b/src/mongo/db/exec/shard_filter.h
index 16cc21d7392..f0b04ae9d4a 100644
--- a/src/mongo/db/exec/shard_filter.h
+++ b/src/mongo/db/exec/shard_filter.h
@@ -90,9 +90,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
@@ -110,4 +110,3 @@ namespace mongo {
     };
 
 }  // namespace mongo
-
diff --git a/src/mongo/db/exec/skip.cpp b/src/mongo/db/exec/skip.cpp
index a0026d2b829..1a8f0ab5d57 100644
--- a/src/mongo/db/exec/skip.cpp
+++ b/src/mongo/db/exec/skip.cpp
@@ -124,11 +124,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* SkipStage::getCommonStats() {
+    const CommonStats* SkipStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* SkipStage::getSpecificStats() {
+    const SpecificStats* SkipStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/skip.h b/src/mongo/db/exec/skip.h
index b61f23a9c7f..ff3982a415c 100644
--- a/src/mongo/db/exec/skip.h
+++ b/src/mongo/db/exec/skip.h
@@ -60,9 +60,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/sort.cpp b/src/mongo/db/exec/sort.cpp
index da8c0bb57e5..6af1a48e319 100644
--- a/src/mongo/db/exec/sort.cpp
+++ b/src/mongo/db/exec/sort.cpp
@@ -483,11 +483,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* SortStage::getCommonStats() {
+    const CommonStats* SortStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* SortStage::getSpecificStats() {
+    const SpecificStats* SortStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/sort.h b/src/mongo/db/exec/sort.h
index 5211747c2ef..2255a5ce82c 100644
--- a/src/mongo/db/exec/sort.h
+++ b/src/mongo/db/exec/sort.h
@@ -161,9 +161,9 @@ namespace mongo {
 
         PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/subplan.cpp b/src/mongo/db/exec/subplan.cpp
index 88cb23e5642..364c429429d 100644
--- a/src/mongo/db/exec/subplan.cpp
+++ b/src/mongo/db/exec/subplan.cpp
@@ -546,11 +546,11 @@ namespace mongo {
         return NULL != _branchResults[i]->cachedSolution.get();
     }
 
-    const CommonStats* SubplanStage::getCommonStats() {
+    const CommonStats* SubplanStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* SubplanStage::getSpecificStats() {
+    const SpecificStats* SubplanStage::getSpecificStats() const {
         return NULL;
     }
 
diff --git a/src/mongo/db/exec/subplan.h b/src/mongo/db/exec/subplan.h
index 190da7988f9..8de399a4983 100644
--- a/src/mongo/db/exec/subplan.h
+++ b/src/mongo/db/exec/subplan.h
@@ -87,9 +87,9 @@ namespace mongo {
 
         PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/text.cpp b/src/mongo/db/exec/text.cpp
index 67596b62157..b049c17b9ff 100644
--- a/src/mongo/db/exec/text.cpp
+++ b/src/mongo/db/exec/text.cpp
@@ -185,11 +185,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* TextStage::getCommonStats() {
+    const CommonStats* TextStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* TextStage::getSpecificStats() {
+    const SpecificStats* TextStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/text.h b/src/mongo/db/exec/text.h
index 6a5d01a818b..4a7364e052d 100644
--- a/src/mongo/db/exec/text.h
+++ b/src/mongo/db/exec/text.h
@@ -118,9 +118,9 @@ namespace mongo {
 
         PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/exec/update.cpp b/src/mongo/db/exec/update.cpp
index 54ae2c68b2d..0430202a241 100644
--- a/src/mongo/db/exec/update.cpp
+++ b/src/mongo/db/exec/update.cpp
@@ -1064,11 +1064,11 @@ namespace mongo {
         return ret.release();
     }
 
-    const CommonStats* UpdateStage::getCommonStats() {
+    const CommonStats* UpdateStage::getCommonStats() const {
         return &_commonStats;
     }
 
-    const SpecificStats* UpdateStage::getSpecificStats() {
+    const SpecificStats* UpdateStage::getSpecificStats() const {
         return &_specificStats;
     }
 
diff --git a/src/mongo/db/exec/update.h b/src/mongo/db/exec/update.h
index c1dbe9a185f..c1a9372eae9 100644
--- a/src/mongo/db/exec/update.h
+++ b/src/mongo/db/exec/update.h
@@ -100,9 +100,9 @@ namespace mongo {
 
         virtual PlanStageStats* getStats();
 
-        virtual const CommonStats* getCommonStats();
+        virtual const CommonStats* getCommonStats() const;
 
-        virtual const SpecificStats* getSpecificStats();
+        virtual const SpecificStats* getSpecificStats() const;
 
         static const char* kStageType;
 
diff --git a/src/mongo/db/query/explain.cpp b/src/mongo/db/query/explain.cpp
index 9274ce3b1de..dc4bf614da8 100644
--- a/src/mongo/db/query/explain.cpp
+++ b/src/mongo/db/query/explain.cpp
@@ -56,7 +56,7 @@ namespace {
     /**
      * Traverse the tree rooted at 'root', and add all tree nodes into the list 'flattened'.
      */
-    void flattenStatsTree(PlanStageStats* root, vector<PlanStageStats*>* flattened) {
+    void flattenStatsTree(const PlanStageStats* root, vector<const PlanStageStats*>* flattened) {
         flattened->push_back(root);
         for (size_t i = 0; i < root->children.size(); ++i) {
             flattenStatsTree(root->children[i], flattened);
@@ -66,7 +66,7 @@ namespace {
     /**
      * Traverse the tree rooted at 'root', and add all nodes into the list 'flattened'.
      */
-    void flattenExecTree(PlanStage* root, vector<PlanStage*>* flattened) {
+    void flattenExecTree(const PlanStage* root, vector<const PlanStage*>* flattened) {
         flattened->push_back(root);
         vector<PlanStage*> children = root->getChildren();
         for (size_t i = 0; i < children.size(); ++i) {
@@ -162,7 +162,7 @@ namespace {
     /**
      * Adds to the plan summary string being built by 'ss' for the execution stage 'stage'.
      */
-    void addStageSummaryStr(PlanStage* stage, mongoutils::str::stream& ss) {
+    void addStageSummaryStr(const PlanStage* stage, mongoutils::str::stream& ss) {
         // First add the stage type string.
         const CommonStats* common = stage->getCommonStats();
         ss << common->stageTypeStr;
@@ -552,7 +552,7 @@ namespace mongo {
         }
 
         // Flatten the stats tree into a list.
-        vector<PlanStageStats*> statsNodes;
+        vector<const PlanStageStats*> statsNodes;
         flattenStatsTree(stats, &statsNodes);
 
         // Iterate over all stages in the tree and get the total number of keys/docs examined.
@@ -676,13 +676,13 @@ namespace mongo {
     }
 
     // static
-    string Explain::getPlanSummary(PlanExecutor* exec) {
+    std::string Explain::getPlanSummary(const PlanExecutor* exec) {
          return getPlanSummary(exec->getRootStage());
     }
 
     // static
-    string Explain::getPlanSummary(PlanStage* root) {
-        vector<PlanStage*> stages;
+    std::string Explain::getPlanSummary(const PlanStage* root) {
+        std::vector<const PlanStage*> stages;
         flattenExecTree(root, &stages);
 
         // Use this stream to build the plan summary string.
@@ -707,7 +707,7 @@ namespace mongo {
     }
 
     // static
-    void Explain::getSummaryStats(PlanExecutor* exec, PlanSummaryStats* statsOut) {
+    void Explain::getSummaryStats(const PlanExecutor* exec, PlanSummaryStats* statsOut) {
         invariant(NULL != statsOut);
 
         PlanStage* root = exec->getRootStage();
@@ -720,7 +720,7 @@ namespace mongo {
 
         // The other fields are aggregations over the stages in the plan tree. We flatten
         // the tree into a list and then compute these aggregations.
-        vector<PlanStage*> stages;
+        std::vector<const PlanStage*> stages;
         flattenExecTree(root, &stages);
 
         for (size_t i = 0; i < stages.size(); i++) {
diff --git a/src/mongo/db/query/explain.h b/src/mongo/db/query/explain.h
index 8b70c30658e..14a9d1289f5 100644
--- a/src/mongo/db/query/explain.h
+++ b/src/mongo/db/query/explain.h
@@ -121,8 +121,8 @@ namespace mongo {
         /**
          * Returns a short plan summary std::string describing the leaves of the query plan.
          */
-        static std::string getPlanSummary(PlanExecutor* exec);
-        static std::string getPlanSummary(PlanStage* root);
+        static std::string getPlanSummary(const PlanExecutor* exec);
+        static std::string getPlanSummary(const PlanStage* root);
 
         /**
          * Fills out 'statsOut' with summary stats using the execution tree contained
@@ -137,7 +137,7 @@ namespace mongo {
          *
          * Does not take ownership of its arguments.
          */
-        static void getSummaryStats(PlanExecutor* exec, PlanSummaryStats* statsOut);
+        static void getSummaryStats(const PlanExecutor* exec, PlanSummaryStats* statsOut);
 
     private:
         /**