include-execution-stats-example.txt

> db.test.save({a: 1})
WriteResult({ "nInserted" : 1 })
> db.test.save({a: 2})
WriteResult({ "nInserted" : 1 })
> db.test.save({a: 3})
WriteResult({ "nInserted" : 1 })
> db.test.runCommand({find: 'test', filter: {a: {$gte: 2}}, includeExecutionStats: true})
{
        "cursor" : {
                "firstBatch" : [
                        {
                                "_id" : ObjectId("5f35bb945edc03d8581bd9c4"),
                                "a" : 2
                        },
                        {
                                "_id" : ObjectId("5f35bb955edc03d8581bd9c5"),
                                "a" : 3
                        }
                ],
                "id" : NumberLong(0),
                "ns" : "test.test"
        },
        "executionStats" : {
                "keysExamined" : 0,
                "docsExamined" : 3,
                "hasSortStage" : false,
                "planSummary" : "COLLSCAN"
        },
        "ok" : 1
}
> db.test.ensureIndex({a: 1})
{
        "createdCollectionAutomatically" : false,
        "numIndexesBefore" : 1,
        "numIndexesAfter" : 2,
        "ok" : 1
}
> db.test.runCommand({find: 'test', filter: {a: {$gte: 2}}, includeExecutionStats: true})
{
        "cursor" : {
                "firstBatch" : [
                        {
                                "_id" : ObjectId("5f35bb945edc03d8581bd9c4"),
                                "a" : 2
                        },
                        {
                                "_id" : ObjectId("5f35bb955edc03d8581bd9c5"),
                                "a" : 3
                        }
                ],
                "id" : NumberLong(0),
                "ns" : "test.test"
        },
        "executionStats" : {
                "keysExamined" : 2,
                "docsExamined" : 2,
                "hasSortStage" : false,
                "planSummary" : "IXSCAN { a: 1 }"
        },
        "ok" : 1
}

include-execution-stats.diff

diff --git a/src/mongo/db/commands/find_cmd.cpp b/src/mongo/db/commands/find_cmd.cpp
index cba4f1d224..22c7caaff7 100644
--- a/src/mongo/db/commands/find_cmd.cpp
+++ b/src/mongo/db/commands/find_cmd.cpp
@@ -483,6 +483,15 @@ public:
                 throw;
             }
 
+            // Need to grab the stats now before we capture the cursor
+            PlanSummaryStats summaryStats;
+            std::string planSummary;
+            bool includeExecutionStats(originalQR.getIncludeExecutionStats());
+            if (includeExecutionStats) {
+                exec->getSummaryStats(&summaryStats);
+                planSummary = exec->getPlanSummary();
+            }
+
             // Set up the cursor for getMore.
             CursorId cursorId = 0;
             if (shouldSaveCursor(opCtx, collection, state, exec.get())) {
@@ -523,6 +532,17 @@ public:
 
             // Generate the response object to send to the client.
             firstBatch.done(cursorId, nss.ns());
+
+            // Now that the cursor response is closed, we can add the execution stats we captured
+            // above
+            if (includeExecutionStats) {
+                auto bodyBuilder = result->getBodyBuilder();
+                BSONObjBuilder executionStatsBuilder(bodyBuilder.subobjStart("executionStats"));
+                executionStatsBuilder.appendNumber("keysExamined", summaryStats.totalKeysExamined);
+                executionStatsBuilder.appendNumber("docsExamined", summaryStats.totalDocsExamined);
+                executionStatsBuilder.appendBool("hasSortStage", summaryStats.hasSortStage);
+                executionStatsBuilder.append("planSummary", planSummary);
+            }
         }
 
         void appendMirrorableRequest(BSONObjBuilder* bob) const override {
diff --git a/src/mongo/db/query/query_request.cpp b/src/mongo/db/query/query_request.cpp
index b9601a5a1f..2f82416b89 100644
--- a/src/mongo/db/query/query_request.cpp
+++ b/src/mongo/db/query/query_request.cpp
@@ -251,6 +251,13 @@ StatusWith<std::unique_ptr<QueryRequest>> QueryRequest::parseFromFindCommand(
             }
 
             qr->_showRecordId = el.boolean();
+        } else if (fieldName == kIncludeExecutionStatsField) {
+            Status status = checkFieldType(el, Bool);
+            if (!status.isOK()) {
+                return status;
+            }
+
+            qr->_includeExecutionStats = el.boolean();
         } else if (fieldName == kTailableField) {
             Status status = checkFieldType(el, Bool);
             if (!status.isOK()) {
@@ -499,6 +506,10 @@ void QueryRequest::asFindCommandInternal(BSONObjBuilder* cmdBuilder) const {
         cmdBuilder->append(kShowRecordIdField, true);
     }
 
+    if (_includeExecutionStats) {
+        cmdBuilder->append(kIncludeExecutionStatsField, true);
+    }
+
     switch (_tailableMode) {
         case TailableModeEnum::kTailable: {
             cmdBuilder->append(kTailableField, true);
diff --git a/src/mongo/db/query/query_request.h b/src/mongo/db/query/query_request.h
index bfb9615dbc..1666e761ae 100644
--- a/src/mongo/db/query/query_request.h
+++ b/src/mongo/db/query/query_request.h
@@ -82,6 +82,7 @@ public:
     static constexpr auto kResumeAfterField = "$_resumeAfter";
     static constexpr auto kUse44SortKeys = "_use44SortKeys";
     static constexpr auto kMaxTimeMSOpOnlyField = "maxTimeMSOpOnly";
+    static constexpr auto kIncludeExecutionStatsField = "includeExecutionStats";
 
     // Field names for sorting options.
     static constexpr auto kNaturalSortField = "$natural";
@@ -449,6 +450,14 @@ public:
         _resumeAfter = resumeAfter;
     }
 
+    bool getIncludeExecutionStats() const {
+        return _includeExecutionStats;
+    }
+
+    void setIncludeExecutionStats(bool includeExecutionStats) {
+        _includeExecutionStats = includeExecutionStats;
+    }
+
     /**
      * Return options as a bit vector.
      */
@@ -575,6 +584,10 @@ private:
     // inside $expr.
     boost::optional<BSONObj> _letParameters;
 
+    // If specified, include explain-style query execution stats as part of the
+    // find return value
+    bool _includeExecutionStats = false;
+
     // Options that can be specified in the OP_QUERY 'flags' header.
     TailableModeEnum _tailableMode = TailableModeEnum::kNormal;
     bool _slaveOk = false;