Changed the inheritance model to remove types

The inheritance model has changed, we no longer need to store an array of
`types` with the model we can just use the classname in `_cls`.

See the upgrade docs for information on how to upgrade
MongoEngine/mongoengine#148

docs/changelog.rst

@@ -2,6 +2,11 @@
 Changelog
 =========
 
+Changes in 0.8
+==============
+- Remove _types and just use _cls for inheritance (MongoEngine/mongoengine#148)
+
+
 Changes in 0.7.X
 ================
 - Unicode fix for repr (MongoEngine/mongoengine#133)

docs/guide/defining-documents.rst

@@ -461,9 +461,10 @@ If a dictionary is passed then the following options are available:
 :attr:`fields` (Default: None)
     The fields to index. Specified in the same format as described above.
 
-:attr:`types` (Default: True)
-    Whether the index should have the :attr:`_types` field added automatically
-    to the start of the index.
+:attr:`cls` (Default: True)
+    If you have polymorphic models that inherit and have `allow_inheritance`
+    turned on, you can configure whether the index should have the
+    :attr:`_cls` field added automatically to the start of the index.
 
 :attr:`sparse` (Default: False)
     Whether the index should be sparse.
@@ -590,14 +591,14 @@ convenient and efficient retrieval of related documents::
 Working with existing data
 --------------------------
 To enable correct retrieval of documents involved in this kind of heirarchy,
-two extra attributes are stored on each document in the database: :attr:`_cls`
-and :attr:`_types`. These are hidden from the user through the MongoEngine
-interface, but may not be present if you are trying to use MongoEngine with
-an existing database. For this reason, you may disable this inheritance
-mechansim, removing the dependency of :attr:`_cls` and :attr:`_types`, enabling
-you to work with existing databases. To disable inheritance on a document
-class, set :attr:`allow_inheritance` to ``False`` in the :attr:`meta`
-dictionary::
+an extra attribute is stored on each document in the database: :attr:`_cls`.
+These are hidden from the user through the MongoEngine interface, but may not
+be present if you are trying to use MongoEngine with an existing database.
+
+For this reason, you may disable this inheritance mechansim, removing the
+dependency of :attr:`_cls`, enabling you to work with existing databases.
+To disable inheritance on a document class, set :attr:`allow_inheritance` to
+``False`` in the :attr:`meta` dictionary::
 
     # Will work with data in an existing collection named 'cmsPage'
     class Page(Document):

docs/upgrade.rst

@@ -2,6 +2,45 @@
 Upgrading
 =========
 
+0.7 to 0.8
+==========
+
+Inheritance
+-----------
+
+The inheritance model has changed, we no longer need to store an array of
+`types` with the model we can just use the classname in `_cls`.  This means
+that you will have to update your indexes for each of your inherited classes
+like so:
+
+    # 1. Declaration of the class
+    class Animal(Document):
+        name = StringField()
+        meta = {
+            'allow_inheritance': True,
+            'indexes': ['name']
+        }
+
+    # 2. Remove _types
+    collection = Animal._get_collection()
+    collection.update({}, {"$unset": {"_types": 1}}, multi=True)
+
+    # 3. Confirm extra data is removed
+    count = collection.find({'_types': {"$exists": True}}).count()
+    assert count == 0
+
+    # 4. Remove indexes
+    info = collection.index_information()
+    indexes_to_drop = [key for key, value in info.iteritems()
+                       if '_types' in dict(value['key'])]
+    for index in indexes_to_drop:
+        collection.drop_index(index)
+
+    # 5. Recreate indexes
+    Animal.objects._ensure_indexes()
+
+
+
 0.6 to 0.7
 ==========