SERVER-22425 execStats in system.profile should only report winning plan

(cherry picked from commit e63efab6aa0d0983e99cf2e2fb193a8d481500d3)

4 files changed, 33 insertions, 8 deletions

diff --git a/src/mongo/db/query/explain.cpp b/src/mongo/db/query/explain.cpp
index ead46646ced..9d8be0587d1 100644
--- a/src/mongo/db/query/explain.cpp
+++ b/src/mongo/db/query/explain.cpp
@@ -496,6 +496,23 @@ void Explain::statsToBSON(const PlanStageStats& stats,
 }
 
 // static
+BSONObj Explain::getWinningPlanStats(const PlanExecutor* exec) {
+    BSONObjBuilder bob;
+    getWinningPlanStats(exec, &bob);
+    return bob.obj();
+}
+
+// static
+void Explain::getWinningPlanStats(const PlanExecutor* exec, BSONObjBuilder* bob) {
+    MultiPlanStage* mps = getMultiPlanStage(exec->getRootStage());
+    unique_ptr<PlanStageStats> winningStats(
+        mps ? std::move(mps->getStats()->children[mps->bestPlanIdx()])
+            : std::move(exec->getRootStage()->getStats()));
+
+    statsToBSON(*winningStats, ExplainCommon::EXEC_STATS, bob, bob);
+}
+
+// static
 void Explain::generatePlannerInfo(PlanExecutor* exec,
                                   PlanStageStats* winnerStats,
                                   const vector<unique_ptr<PlanStageStats>>& rejectedStats,
diff --git a/src/mongo/db/query/explain.h b/src/mongo/db/query/explain.h
index 069d89d7cb4..2fd6314edfd 100644
--- a/src/mongo/db/query/explain.h
+++ b/src/mongo/db/query/explain.h
@@ -101,6 +101,17 @@ public:
                               BSONObjBuilder* out);
 
     /**
+     * Converts the PlanExecutor's winning plan stats tree to BSON and returns to the caller.
+     */
+    static BSONObj getWinningPlanStats(const PlanExecutor* exec);
+
+    /**
+     * Converts the PlanExecutor's winning plan stats tree to BSON and returns the result through
+     * the out-parameter 'bob'.
+     */
+    static void getWinningPlanStats(const PlanExecutor* exec, BSONObjBuilder* bob);
+
+    /**
      * Converts the stats tree 'stats' into a corresponding BSON object containing
      * explain information.
      *
diff --git a/src/mongo/db/query/explain_common.h b/src/mongo/db/query/explain_common.h
index f76c6d348cf..750f207a2a5 100644
--- a/src/mongo/db/query/explain_common.h
+++ b/src/mongo/db/query/explain_common.h
@@ -53,8 +53,8 @@ public:
         // execution tree. String alias is "execStats".
         EXEC_STATS = 1,
 
-        // At this second-highest verbosity level, we generate the execution stats for each
-        // rejected plan as well as the winning plan. String alias is "allPlansExecution".
+        // At this verbosity level, we generate the execution stats for each rejected plan as
+        // well as the winning plan. String alias is "allPlansExecution".
         EXEC_ALL_PLANS = 2,
     };
 
diff --git a/src/mongo/db/query/find.cpp b/src/mongo/db/query/find.cpp
index 89c356a3fe8..2aa710611b4 100644
--- a/src/mongo/db/query/find.cpp
+++ b/src/mongo/db/query/find.cpp
@@ -176,9 +176,8 @@ void endQueryOp(OperationContext* txn,
     // Set debug information for consumption by the profiler only.
     if (dbProfilingLevel > 0) {
         // Get BSON stats.
-        unique_ptr<PlanStageStats> execStats(exec.getStats());
         BSONObjBuilder statsBob;
-        Explain::statsToBSON(*execStats, &statsBob);
+        Explain::getWinningPlanStats(&exec, &statsBob);
         curop->debug().execStats.set(statsBob.obj());
 
         // Replace exec stats with plan summary if stats cannot fit into CachedBSONObj.
@@ -235,8 +234,7 @@ void generateBatch(int ntoreturn,
 
     if (PlanExecutor::DEAD == *state || PlanExecutor::FAILURE == *state) {
         // Propagate this error to caller.
-        const unique_ptr<PlanStageStats> stats(exec->getStats());
-        error() << "getMore executor error, stats: " << Explain::statsToBSON(*stats);
+        error() << "getMore executor error, stats: " << Explain::getWinningPlanStats(exec);
         uasserted(17406, "getMore executor error: " + WorkingSetCommon::toStatusString(obj));
     }
 }
@@ -619,9 +617,8 @@ std::string runQuery(OperationContext* txn,
 
     // Caller expects exceptions thrown in certain cases.
     if (PlanExecutor::FAILURE == state || PlanExecutor::DEAD == state) {
-        const unique_ptr<PlanStageStats> stats(exec->getStats());
         error() << "Plan executor error during find: " << PlanExecutor::statestr(state)
-                << ", stats: " << Explain::statsToBSON(*stats);
+                << ", stats: " << Explain::getWinningPlanStats(exec.get());
         uasserted(17144, "Executor error: " + WorkingSetCommon::toStatusString(obj));
     }