SERVER-23191 group should pass an owned BSONObj to the reduce function

(cherry picked from commit 6adda9f7dde0bf62b9ff8d27ade8f1bb6e574fec)

2 files changed, 22 insertions, 1 deletions

diff --git a/jstests/core/group9.js b/jstests/core/group9.js
new file mode 100644
index 00000000000..a7d9a0d128e
--- /dev/null
+++ b/jstests/core/group9.js
@@ -0,0 +1,20 @@
+(function() {
+    'use strict';
+    var t = db.group_owned;
+    t.drop();
+
+    assert.writeOK(t.insert({_id: 1, subdoc: {id: 1}}));
+    assert.writeOK(t.insert({_id: 2, subdoc: {id: 2}}));
+
+    var result = t.group({
+        key: {'subdoc.id': 1},
+        reduce: function(doc, value) {
+            value.subdoc = doc.subdoc;
+            return value;
+        },
+        initial: {},
+        finalize: function(res) {}
+    });
+
+    assert(result.length == 2);
+}());
diff --git a/src/mongo/db/exec/group.cpp b/src/mongo/db/exec/group.cpp
index 4ce1d4031db..31a72df4772 100644
--- a/src/mongo/db/exec/group.cpp
+++ b/src/mongo/db/exec/group.cpp
@@ -148,7 +148,8 @@ Status GroupStage::processObject(const BSONObj& obj) {
         }
     }
 
-    _scope->setObject("obj", obj, true);
+    BSONObj objCopy = obj.getOwned();
+    _scope->setObject("obj", objCopy, true);
     _scope->setNumber("n", n - 1);
 
     try {