diff --git a/cubes/backends/mongo/browser.py b/cubes/backends/mongo/browser.py
index 462d7d0e..75e9e25f 100644
--- a/cubes/backends/mongo/browser.py
+++ b/cubes/backends/mongo/browser.py
@@ -1,26 +1,28 @@
-from ...logging import get_logger
-from ...errors import *
-from ...browser import *
-from ...computation import *
-from ...statutils import calculators_for_aggregates, available_calculators
-from cubes import statutils
-from .mapper import MongoCollectionMapper
-from .datesupport import MongoDateSupport
-from .functions import get_aggregate_function, available_aggregate_functions
-from .util import to_json_safe, collapse_record
-
 import collections
 import copy
-import pymongo
-import bson
+from datetime import datetime
+from functools import partial
+from itertools import groupby
+import json
 import re
 
+import bson
+from cubes import statutils
 from dateutil.relativedelta import relativedelta
-from datetime import datetime
-from itertools import groupby
-from functools import partial
+import pymongo
 import pytz
 
+from ...browser import *
+from ...computation import *
+from ...errors import *
+from ...logging import get_logger
+from ...statutils import calculators_for_aggregates, available_calculators
+from .datesupport import MongoDateSupport
+from .functions import get_aggregate_function, available_aggregate_functions
+from .mapper import MongoCollectionMapper
+from .util import to_json_safe, collapse_record
+from pymongo.cursor import Cursor
+
 
 tz_utc = pytz.timezone('UTC')
 
@@ -202,7 +204,7 @@ def provide_members(self, cell, dimension, depth=None, hierarchy=None,
 
         attributes = []
         for level in levels:
-           attributes += level.attributes
+            attributes += level.attributes
 
         drilldown = Drilldown([(dimension, hierarchy, levels[-1])], cell)
 
@@ -392,14 +394,13 @@ def _date_transform(item, date_field):
                 raise BrowserError("Measure cannot be in different database "
                                    "or collection than browser: %r" % phys)
 
-            aggregate_fn_pairs.append( ( escape_level(agg.ref()), sum ) )
-
+            aggregate_fn_pairs.append( ( escape_level(agg.ref()), function ) )
 
             if phys.group:
                 group = phys.group
             elif function:
                 group_applicator = function["group_by"]
-                group = group_applicator(escape_level(agg.ref()))
+                group = group_applicator(escape_level(agg.measure or agg.ref()))
             else:
                 raise ModelError("Neither function or mapping group specified "
                                  "for aggregate '%s' in cube '%s'"
@@ -416,9 +417,10 @@ def _date_transform(item, date_field):
             pipeline = []
 
         pipeline.append({ "$match": query_obj })
+        pipeline.append({ "$group": group_obj })
         if fields_obj:
             pipeline.append({ "$project": fields_obj })
-        pipeline.append({ "$group": group_obj })
+        
 
         if not timezone_shift_processing:
             if order:
@@ -436,11 +438,15 @@ def _date_transform(item, date_field):
             pipeline.append({ "$limit": page_size })
 
         result_items = []
-        self.logger.debug("PIPELINE: %s", pipeline)
-
-        results = self.data_store.aggregate(pipeline).get('result', [])
+        self.logger.debug("PIPELINE: %s", json.dumps(pipeline))
+        
+        results = self.data_store.aggregate(pipeline)
+        # backwards compatibility
+        # since Pymongo 3.x CommandCursor is always returned 
+        if isinstance(results, Cursor):
+            results = results.get('result', [])
         results = [date_transform(r) for r in results]
-
+        
         if timezone_shift_processing:
             dategrouping = ['year', 'month', 'week', 'day', 'hour', 'minute']
             datenormalize = ['year', 'month', 'week', 'dow', 'day', 'hour', 'minute']
diff --git a/cubes/backends/mongo/mapper.py b/cubes/backends/mongo/mapper.py
index 821a1905..d7f25e6b 100644
--- a/cubes/backends/mongo/mapper.py
+++ b/cubes/backends/mongo/mapper.py
@@ -162,7 +162,8 @@ def __init__(self, cube, database, collection, mappings=None, **options):
         self.database = database
         self.collection = collection
         self.mappings = mappings or cube.mappings
-
+        
+    
     def physical(self, attribute, locale=None):
         """Returns physical reference as tuple for `attribute`, which should
         be an instance of :class:`cubes.model.Attribute`. If there is no
@@ -180,6 +181,7 @@ def physical(self, attribute, locale=None):
             # TODO: should default to non-localized reference if no mapping
             # was found?
             mapped_ref = self.cube.mappings.get(logical)
+                         
 
             if mapped_ref:
                 reference = coalesce_physical(self, mapped_ref)
diff --git a/cubes/backends/mongo/store.py b/cubes/backends/mongo/store.py
index 29bcefb6..f9af5408 100644
--- a/cubes/backends/mongo/store.py
+++ b/cubes/backends/mongo/store.py
@@ -9,4 +9,8 @@ def __init__(self, url, database=None, collection=None, **options):
         self.client = pymongo.MongoClient(url, read_preference=pymongo.read_preferences.ReadPreference.SECONDARY)
         self.database = database
         self.collection = collection
+        self.options = options
+        self.store_type = options['store_type']
+        
+