added map/reduce support via QuerySet.map_reduce. map_reduce operations respect query specs and ordering, but ordering is currently only applied to map/reduce collection. map/reduce may eventually require its own QuerySet to avoid slicing conflicts. results are returned as lists of MapReduceDocument objects, dynamic objects representing the query. tests and documentation included. considered in the neighborhood of 'good start'.

mongoengine/document.py

@@ -114,3 +114,44 @@ class Document(BaseDocument):
         """
         db = _get_db()
         db.drop_collection(cls._meta['collection'])
+
+
+class MapReduceDocument(object):
+    """A document returned from a map/reduce query.
+    
+    :param collection: An instance of :class:`~pymongo.Collection`
+    :param key: Document/result key, often an instance of 
+                :class:`~pymongo.objectid.ObjectId`. If supplied as 
+                an ``ObjectId`` found in the given ``collection``, 
+                the object can be accessed via the ``key_object`` property.
+    :param value: The result(s) for this key. If given as a dictionary,
+                  each key in the dictionary will be available as
+                  an instance attribute.
+    
+    .. versionadded:: 0.2.2
+ 
+    """
+    
+    def __init__(self, collection, key, value):
+        self._collection = collection
+        self.key = key
+        self.value = value
+        
+        if isinstance(value, dict):
+            # create attributes for each named result
+            for k, v in value.iteritems():
+                setattr(self, k, v)
+    
+    @property
+    def object(self):
+        """Lazy-load the object referenced by ``self.key``. If ``self.key``
+        is not an ``ObjectId``, simply return ``self.key``.
+        """
+        if not isinstance(self.key, pymongo.objectid.ObjectId):
+            return self.key
+        if not hasattr(self, "_key_object"):
+            self._key_object = self._collection.find_one(self.key)
+            return self._key_object
+        return self._key_object
+
+