SERVER-37007 Add planSummary to idleCursor

4 files changed, 35 insertions, 5 deletions

diff --git a/src/mongo/db/clientcursor.cpp b/src/mongo/db/clientcursor.cpp
index 756f1fbc7eb..92e6a1ffb30 100644
--- a/src/mongo/db/clientcursor.cpp
+++ b/src/mongo/db/clientcursor.cpp
@@ -47,6 +47,7 @@
 #include "mongo/db/commands/server_status_metric.h"
 #include "mongo/db/cursor_server_params.h"
 #include "mongo/db/jsobj.h"
+#include "mongo/db/query/explain.h"
 #include "mongo/db/repl/repl_client_info.h"
 #include "mongo/db/repl/replication_coordinator.h"
 #include "mongo/util/background.h"
@@ -92,7 +93,8 @@ ClientCursor::ClientCursor(ClientCursorParams params,
       _exec(std::move(params.exec)),
       _operationUsingCursor(operationUsingCursor),
       _lastUseDate(now),
-      _createdDate(now) {
+      _createdDate(now),
+      _planSummary(Explain::getPlanSummary(_exec.get())) {
     invariant(_cursorManager);
     invariant(_exec);
     invariant(_operationUsingCursor);
@@ -143,6 +145,7 @@ GenericCursor ClientCursor::toGenericCursor() const {
     gc.setLastAccessDate(getLastUseDate());
     gc.setCreatedDate(getCreatedDate());
     gc.setNBatchesReturned(getNBatches());
+    gc.setPlanSummary(getPlanSummary());
     if (auto opCtx = _operationUsingCursor) {
         gc.setOperationUsingCursorId(opCtx->getOpID());
     }
diff --git a/src/mongo/db/clientcursor.h b/src/mongo/db/clientcursor.h
index 96cae17da5b..83b326b93da 100644
--- a/src/mongo/db/clientcursor.h
+++ b/src/mongo/db/clientcursor.h
@@ -209,6 +209,14 @@ public:
         return _createdDate;
     }
 
+    void setPlanSummary(std::string ps) {
+        _planSummary = std::move(ps);
+    }
+
+    StringData getPlanSummary() const {
+        return StringData(_planSummary);
+    }
+
     /**
      * Returns a generic cursor containing diagnostics about this cursor.
      * The caller must either have this cursor pinned or hold a mutex from the cursor manager.
@@ -374,6 +382,9 @@ private:
 
     Date_t _lastUseDate;
     Date_t _createdDate;
+
+    // A string with the plan summary of the cursor's query.
+    std::string _planSummary;
 };
 
 /**
diff --git a/src/mongo/db/generic_cursor.idl b/src/mongo/db/generic_cursor.idl
index 24661fa9221..2792a9db88e 100644
--- a/src/mongo/db/generic_cursor.idl
+++ b/src/mongo/db/generic_cursor.idl
@@ -71,6 +71,10 @@ structs:
       lsid:
         type: LogicalSessionId
         optional: true
+      planSummary: 
+        description: The plan summary of this cursor's query.
+        type: string
+        optional: true
       operationUsingCursorId:
         description: The op ID of the operation pinning the cursor. Will be empty for idle cursors.
         type: long
diff --git a/src/mongo/db/pipeline/mongo_process_common.cpp b/src/mongo/db/pipeline/mongo_process_common.cpp
index aae991ba05f..1c97921e237 100644
--- a/src/mongo/db/pipeline/mongo_process_common.cpp
+++ b/src/mongo/db/pipeline/mongo_process_common.cpp
@@ -78,10 +78,22 @@ std::vector<BSONObj> MongoProcessCommon::getCurrentOps(
     if (cursorMode == CurrentOpCursorMode::kIncludeCursors) {
 
         for (auto&& cursor : getIdleCursors(expCtx, userMode)) {
-            ops.push_back(BSON("type"
-                               << "idleCursor"
-                               << "cursor"
-                               << cursor.toBSON()));
+            BSONObjBuilder cursorObj;
+            cursorObj.append("type", "idleCursor");
+            // On mongos, planSummary is not present.
+            auto planSummaryData = cursor.getPlanSummary();
+            if (planSummaryData) {
+                auto planSummaryText = planSummaryData->toString();
+                // Plan summary has to appear in the top level object, not the cursor object.
+                // We remove it, create the op, then put it back.
+                cursor.setPlanSummary(boost::none);
+                cursorObj.append("planSummary", planSummaryText);
+                cursorObj.append("cursor", cursor.toBSON());
+                cursor.setPlanSummary(StringData(planSummaryText));
+            } else {
+                cursorObj.append("cursor", cursor.toBSON());
+            }
+            ops.emplace_back(cursorObj.obj());
         }
     }