Added no_dereference context manager (#82)

Reorganised the context_managers as well

docs/apireference.rst

@@ -7,7 +7,6 @@ Connecting
 
 .. autofunction:: mongoengine.connect
 .. autofunction:: mongoengine.register_connection
-.. autoclass:: mongoengine.SwitchDB
 
 Documents
 =========
@@ -35,6 +34,13 @@ Documents
 .. autoclass:: mongoengine.ValidationError
   :members:
 
+Context Managers
+================
+
+.. autoclass:: mongoengine.context_managers.switch_db
+.. autoclass:: mongoengine.context_managers.no_dereference
+.. autoclass:: mongoengine.context_managers.query_counter
+
 Querying
 ========
 

docs/changelog.rst

@@ -32,8 +32,9 @@ Changes in 0.8.X
 - Fixed inheritance and unique index creation (#140)
 - Fixed reverse delete rule with inheritance (#197)
 - Fixed validation for GenericReferences which havent been dereferenced
-- Added SwitchDB context manager (#106)
+- Added switch_db context manager (#106)
 - Added switch_db method to document instances (#106)
+- Added no_dereference context manager (#82)
 
 Changes in 0.7.9
 ================

docs/guide/connecting.rst

@@ -75,15 +75,15 @@ Switch Database Context Manager
 ===============================
 
 Sometimes you might want to switch the database to query against for a class.
-The SwitchDB context manager allows you to change the database alias for a
-class eg ::
+The :class:`~mongoengine.context_managers.switch_db` context manager allows
+you to change the database alias for a class eg ::
 
-        from mongoengine import SwitchDB
+        from mongoengine.context_managers import switch_db
 
         class User(Document):
             name = StringField()
 
             meta = {"db_alias": "user-db"}
 
-        with SwitchDB(User, 'archive-user-db') as User:
+        with switch_db(User, 'archive-user-db') as User:
             User(name="Ross").save()  # Saves the 'archive-user-db'

docs/guide/querying.rst

@@ -93,7 +93,7 @@ may used with :class:`~mongoengine.GeoPointField`\ s:
   [(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.
+  distance.
 
 
 Querying lists
@@ -369,6 +369,22 @@ references to the depth of 1 level.  If you have more complicated documents and
 want to dereference more of the object at once then increasing the :attr:`max_depth`
 will dereference more levels of the document.
 
+Turning off dereferencing
+-------------------------
+
+Sometimes for performance reasons you don't want to automatically dereference
+data .  To turn off all dereferencing you can use the
+:class:`~mongoengine.context_managers.no_dereference` context manager::
+
+    with no_dereference(Post) as Post:
+        post = Post.objects.first()
+        assert(isinstance(post.author, ObjectId))
+
+.. note::
+
+    :class:`~mongoengine.context_managers.no_dereference` only works on the
+    Default QuerySet manager.
+
 Advanced queries
 ================
 Sometimes calling a :class:`~mongoengine.queryset.QuerySet` object with keyword