Added support for $maxDistance (#179)

docs/changelog.rst

@@ -27,6 +27,7 @@ Changes in 0.8.X
 - Simplified Q objects, removed QueryTreeTransformerVisitor (#98) (#171)
 - FileFields now copyable (#198)
 - Querysets now return clones and are no longer edit in place (#56)
+- Added support for $maxDistance (#179)
 
 Changes in 0.7.9
 ================

docs/guide/querying.rst

@@ -92,6 +92,8 @@ may used with :class:`~mongoengine.GeoPointField`\ s:
 * ``within_polygon`` -- filter documents to those within a given polygon (e.g.
   [(41.91,-87.69), (41.92,-87.68), (41.91,-87.65), (41.89,-87.65)]).
   .. note:: Requires Mongo Server 2.0
+* ``max_distance`` -- can be added to your location queries to set a maximum
+distance.
 
 
 Querying lists

mongoengine/queryset/transform.py

@@ -9,7 +9,8 @@ __all__ = ('query', 'update')
 COMPARISON_OPERATORS = ('ne', 'gt', 'gte', 'lt', 'lte', 'in', 'nin', 'mod',
                           'all', 'size', 'exists', 'not')
 GEO_OPERATORS        = ('within_distance', 'within_spherical_distance',
-                        'within_box', 'within_polygon', 'near', 'near_sphere')
+                        'within_box', 'within_polygon', 'near', 'near_sphere',
+                        'max_distance')
 STRING_OPERATORS     = ('contains', 'icontains', 'startswith',
                         'istartswith', 'endswith', 'iendswith',
                         'exact', 'iexact')
@@ -97,6 +98,8 @@ def query(_doc_cls=None, _field_operation=False, **query):
                     value = {'$nearSphere': value}
                 elif op == 'within_box':
                     value = {'$within': {'$box': value}}
+                elif op == "max_distance":
+                    value = {'$maxDistance': value}
                 else:
                     raise NotImplementedError("Geo method '%s' has not "
                                               "been implemented" % op)

tests/queryset/queryset.py

@@ -2238,6 +2238,12 @@ class QuerySetTest(unittest.TestCase):
         self.assertEqual(events.count(), 3)
         self.assertEqual(list(events), [event3, event1, event2])
 
+        # find events within 10 degrees of san francisco
+        point = [37.7566023, -122.415579]
+        events = Event.objects(location__near=point, location__max_distance=10)
+        self.assertEqual(events.count(), 1)
+        self.assertEqual(events[0], event2)
+
         # find events within 10 degrees of san francisco
         point_and_distance = [[37.7566023, -122.415579], 10]
         events = Event.objects(location__within_distance=point_and_distance)
@@ -2317,6 +2323,10 @@ class QuerySetTest(unittest.TestCase):
         );
         self.assertEqual(points.count(), 2)
 
+        points = Point.objects(location__near_sphere=[-122, 37.5],
+                               location__max_distance=60 / earth_radius);
+        self.assertEqual(points.count(), 2)
+
         # Finds both points, but orders the north point first because it's
         # closer to the reference point to the north.
         points = Point.objects(location__near_sphere=[-122, 38.5])