diff --git a/AUTHORS b/AUTHORS
index 37170ffa..f64093d8 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -223,3 +223,4 @@ that much better:
  * Kiryl Yermakou (https://github.com/rma4ok)
  * Matthieu Rigal (https://github.com/MRigal)
  * Charanpal Dhanjal (https://github.com/charanpald)
+ * Emmanuel Leblond (https://github.com/touilleMan)
diff --git a/docs/changelog.rst b/docs/changelog.rst
index ffbc8c54..b9ad5b0e 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -19,6 +19,13 @@ Changes in 0.9.X - DEV
 - Added __ support to escape field name in fields lookup keywords that match operators names #949
 - Support for PyMongo 3+ #946
 - Fix for issue where FileField deletion did not free space in GridFS. 
+- No_dereference() not respected on embedded docs containing reference. #517
+- Document save raise an exception if save_condition fails #1005
+- Fixes some internal _id handling issue. #961
+- Updated URL and Email Field regex validators, added schemes argument to URLField validation. #652
+- Removed get_or_create() deprecated since 0.8.0. #300
+- Capped collection multiple of 256. #1011
+- Added `BaseQuerySet.aggregate_sum` and `BaseQuerySet.aggregate_average` methods.
 
 Changes in 0.9.0
 ================
diff --git a/docs/guide/defining-documents.rst b/docs/guide/defining-documents.rst
index 79332493..8f7382ee 100644
--- a/docs/guide/defining-documents.rst
+++ b/docs/guide/defining-documents.rst
@@ -315,12 +315,12 @@ reference with a delete rule specification.  A delete rule is specified by
 supplying the :attr:`reverse_delete_rule` attributes on the
 :class:`ReferenceField` definition, like this::
 
-    class Employee(Document):
+    class ProfilePage(Document):
         ...
-        profile_page = ReferenceField('ProfilePage', reverse_delete_rule=mongoengine.NULLIFY)
+        employee = ReferenceField('Employee', reverse_delete_rule=mongoengine.CASCADE)
 
 The declaration in this example means that when an :class:`Employee` object is
-removed, the :class:`ProfilePage` that belongs to that employee is removed as
+removed, the :class:`ProfilePage` that references that employee is removed as
 well.  If a whole batch of employees is removed, all profile pages that are
 linked are removed as well.
 
@@ -447,8 +447,10 @@ A :class:`~mongoengine.Document` may use a **Capped Collection** by specifying
 :attr:`max_documents` and :attr:`max_size` in the :attr:`meta` dictionary.
 :attr:`max_documents` is the maximum number of documents that is allowed to be
 stored in the collection, and :attr:`max_size` is the maximum size of the
-collection in bytes. If :attr:`max_size` is not specified and
-:attr:`max_documents` is, :attr:`max_size` defaults to 10000000 bytes (10MB).
+collection in bytes. :attr:`max_size` is rounded up to the next multiple of 256
+by MongoDB internally and mongoengine before. Use also a multiple of 256 to
+avoid confusions. If :attr:`max_size` is not specified and
+:attr:`max_documents` is, :attr:`max_size` defaults to 10485760 bytes (10MB).
 The following example shows a :class:`Log` document that will be limited to
 1000 entries and 2MB of disk space::
 
@@ -465,19 +467,26 @@ You can specify indexes on collections to make querying faster. This is done
 by creating a list of index specifications called :attr:`indexes` in the
 :attr:`~mongoengine.Document.meta` dictionary, where an index specification may
 either be a single field name, a tuple containing multiple field names, or a
-dictionary containing a full index definition. A direction may be specified on
-fields by prefixing the field name with a **+** (for ascending) or a **-** sign
-(for descending). Note that direction only matters on multi-field indexes.
-Text indexes may be specified by prefixing the field name with a **$**. ::
+dictionary containing a full index definition.
+
+A direction may be specified on fields by prefixing the field name with a
+**+** (for ascending) or a **-** sign (for descending). Note that direction
+only matters on multi-field indexes. Text indexes may be specified by prefixing
+the field name with a **$**. Hashed indexes may be specified by prefixing
+the field name with a **#**::
 
     class Page(Document):
+        category = IntField()
         title = StringField()
         rating = StringField()
         created = DateTimeField()
         meta = {
             'indexes': [
                 'title',
+                '$title',  # text index
+                '#title',  # hashed index
                 ('title', '-rating'),
+                ('category', '_cls'),
                 {
                     'fields': ['created'],
                     'expireAfterSeconds': 3600
@@ -532,11 +541,14 @@ There are a few top level defaults for all indexes that can be set::
 :attr:`index_background` (Optional)
     Set the default value for if an index should be indexed in the background
 
+:attr:`index_cls` (Optional)
+    A way to turn off a specific index for _cls.
+
 :attr:`index_drop_dups` (Optional)
     Set the default value for if an index should drop duplicates
 
-:attr:`index_cls` (Optional)
-    A way to turn off a specific index for _cls.
+.. note:: Since MongoDB 3.0 drop_dups is not supported anymore. Raises a Warning
+    and has no effect
 
 
 Compound Indexes and Indexing sub documents
diff --git a/docs/guide/querying.rst b/docs/guide/querying.rst
index 9861ce56..1cde82cb 100644
--- a/docs/guide/querying.rst
+++ b/docs/guide/querying.rst
@@ -263,21 +263,11 @@ no document matches the query, and
 if more than one document matched the query.  These exceptions are merged into
 your document definitions eg: `MyDoc.DoesNotExist`
 
-A variation of this method exists,
-:meth:`~mongoengine.queryset.QuerySet.get_or_create`, that will create a new
-document with the query arguments if no documents match the query. An
-additional keyword argument, :attr:`defaults` may be provided, which will be
-used as default values for the new document, in the case that it should need
-to be created::
-
-    >>> a, created = User.objects.get_or_create(name='User A', defaults={'age': 30})
-    >>> b, created = User.objects.get_or_create(name='User A', defaults={'age': 40})
-    >>> a.name == b.name and a.age == b.age
-    True
-
-.. warning::
-    :meth:`~mongoengine.queryset.QuerySet.get_or_create` method is deprecated
-    since :mod:`mongoengine` 0.8.
+A variation of this method, get_or_create() existed, but it was unsafe. It
+could not be made safe, because there are no transactions in mongoDB. Other
+approaches should be investigated, to ensure you don't accidentally duplicate
+data when using something similar to this method. Therefore it was deprecated
+in 0.8 and removed in 0.10.
 
 Default Document queries
 ========================
diff --git a/mongoengine/base/document.py b/mongoengine/base/document.py
index 3eba16ca..1049eabd 100644
--- a/mongoengine/base/document.py
+++ b/mongoengine/base/document.py
@@ -184,7 +184,7 @@ class BaseDocument(object):
             self__initialised = False
         # Check if the user has created a new instance of a class
         if (self._is_document and self__initialised
-                and self__created and name == self._meta['id_field']):
+                and self__created and name == self._meta.get('id_field')):
             super(BaseDocument, self).__setattr__('_created', False)
 
         super(BaseDocument, self).__setattr__(name, value)
@@ -672,7 +672,7 @@ class BaseDocument(object):
 
     @classmethod
     def _get_collection_name(cls):
-        """Returns the collection name for this class.
+        """Returns the collection name for this class. None for abstract class
         """
         return cls._meta.get('collection', None)
 
@@ -782,7 +782,7 @@ class BaseDocument(object):
         allow_inheritance = cls._meta.get('allow_inheritance',
                                           ALLOW_INHERITANCE)
         include_cls = (allow_inheritance and not spec.get('sparse', False) and
-                       spec.get('cls',  True))
+                       spec.get('cls',  True) and '_cls' not in spec['fields'])
 
         # 733: don't include cls if index_cls is False unless there is an explicit cls with the index
         include_cls = include_cls and (spec.get('cls', False) or cls._meta.get('index_cls', True))
@@ -795,16 +795,25 @@ class BaseDocument(object):
 
             # ASCENDING from +
             # DESCENDING from -
-            # GEO2D from *
             # TEXT from $
+            # HASHED from #
+            # GEOSPHERE from (
+            # GEOHAYSTACK from )
+            # GEO2D from *
             direction = pymongo.ASCENDING
             if key.startswith("-"):
                 direction = pymongo.DESCENDING
-            elif key.startswith("*"):
-                direction = pymongo.GEO2D
             elif key.startswith("$"):
                 direction = pymongo.TEXT
-            if key.startswith(("+", "-", "*", "$")):
+            elif key.startswith("#"):
+                direction = pymongo.HASHED
+            elif key.startswith("("):
+                direction = pymongo.GEOSPHERE
+            elif key.startswith(")"):
+                direction = pymongo.GEOHAYSTACK
+            elif key.startswith("*"):
+                direction = pymongo.GEO2D
+            if key.startswith(("+", "-", "*", "$", "#", "(", ")")):
                 key = key[1:]
 
             # Use real field name, do it manually because we need field
@@ -827,7 +836,8 @@ class BaseDocument(object):
             index_list.append((key, direction))
 
         # Don't add cls to a geo index
-        if include_cls and direction is not pymongo.GEO2D:
+        if include_cls and direction not in (
+                pymongo.GEO2D, pymongo.GEOHAYSTACK, pymongo.GEOSPHERE):
             index_list.insert(0, ('_cls', 1))
 
         if index_list:
@@ -973,8 +983,13 @@ class BaseDocument(object):
                 if hasattr(getattr(field, 'field', None), 'lookup_member'):
                     new_field = field.field.lookup_member(field_name)
                 else:
-                   # Look up subfield on the previous field
-                    new_field = field.lookup_member(field_name)
+                    # Look up subfield on the previous field or raise
+                    try:
+                        new_field = field.lookup_member(field_name)
+                    except AttributeError:
+                        raise LookUpError('Cannot resolve subfield or operator {} '
+                                          'on the field {}'.format(
+                                              field_name, field.name))
                 if not new_field and isinstance(field, ComplexBaseField):
                     if hasattr(field.field, 'document_type') and cls._dynamic \
                             and field.field.document_type._dynamic:
diff --git a/mongoengine/base/fields.py b/mongoengine/base/fields.py
index 91f95b4f..5fae2695 100644
--- a/mongoengine/base/fields.py
+++ b/mongoengine/base/fields.py
@@ -290,6 +290,7 @@ class ComplexBaseField(BaseField):
                 return value
 
         if self.field:
+            self.field._auto_dereference = self._auto_dereference
             value_dict = dict([(key, self.field.to_python(item))
                                for key, item in value.items()])
         else:
@@ -424,8 +425,11 @@ class ObjectIdField(BaseField):
     """
 
     def to_python(self, value):
-        if not isinstance(value, ObjectId):
-            value = ObjectId(value)
+        try:
+            if not isinstance(value, ObjectId):
+                value = ObjectId(value)
+        except:
+            pass
         return value
 
     def to_mongo(self, value):
diff --git a/mongoengine/base/metaclasses.py b/mongoengine/base/metaclasses.py
index 8a25ff3d..d4c26bfe 100644
--- a/mongoengine/base/metaclasses.py
+++ b/mongoengine/base/metaclasses.py
@@ -385,15 +385,17 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
         new_class._auto_id_field = getattr(parent_doc_cls,
                                            '_auto_id_field', False)
         if not new_class._meta.get('id_field'):
+            # After 0.10, find not existing names, instead of overwriting
+            id_name, id_db_name = cls.get_auto_id_names(new_class)
             new_class._auto_id_field = True
-            new_class._meta['id_field'] = 'id'
-            new_class._fields['id'] = ObjectIdField(db_field='_id')
-            new_class._fields['id'].name = 'id'
-            new_class.id = new_class._fields['id']
-
-        # Prepend id field to _fields_ordered
-        if 'id' in new_class._fields and 'id' not in new_class._fields_ordered:
-            new_class._fields_ordered = ('id', ) + new_class._fields_ordered
+            new_class._meta['id_field'] = id_name
+            new_class._fields[id_name] = ObjectIdField(db_field=id_db_name)
+            new_class._fields[id_name].name = id_name
+            new_class.id = new_class._fields[id_name]
+            new_class._db_field_map[id_name] = id_db_name
+            new_class._reverse_db_field_map[id_db_name] = id_name
+            # Prepend id field to _fields_ordered
+            new_class._fields_ordered = (id_name, ) + new_class._fields_ordered
 
         # Merge in exceptions with parent hierarchy
         exceptions_to_merge = (DoesNotExist, MultipleObjectsReturned)
@@ -408,6 +410,19 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
 
         return new_class
 
+    def get_auto_id_names(self):
+        id_name, id_db_name = ('id', '_id')
+        if id_name not in self._fields and \
+                id_db_name not in (v.db_field for v in self._fields.values()):
+            return id_name, id_db_name
+        id_basename, id_db_basename, i = 'auto_id', '_auto_id', 0
+        while id_name in self._fields or \
+                id_db_name in (v.db_field for v in self._fields.values()):
+            id_name = '{0}_{1}'.format(id_basename, i)
+            id_db_name = '{0}_{1}'.format(id_db_basename, i)
+            i += 1
+        return id_name, id_db_name
+
 
 class MetaDict(dict):
 
diff --git a/mongoengine/dereference.py b/mongoengine/dereference.py
index 0428397c..8e8920d4 100644
--- a/mongoengine/dereference.py
+++ b/mongoengine/dereference.py
@@ -128,21 +128,25 @@ class DeReference(object):
         """
         object_map = {}
         for collection, dbrefs in self.reference_map.iteritems():
-            refs = [dbref for dbref in dbrefs
-                    if unicode(dbref).encode('utf-8') not in object_map]
             if hasattr(collection, 'objects'):  # We have a document class for the refs
+                col_name = collection._get_collection_name()
+                refs = [dbref for dbref in dbrefs
+                        if (col_name, dbref) not in object_map]
                 references = collection.objects.in_bulk(refs)
                 for key, doc in references.iteritems():
-                    object_map[key] = doc
+                    object_map[(col_name, key)] = doc
             else:  # Generic reference: use the refs data to convert to document
                 if isinstance(doc_type, (ListField, DictField, MapField,)):
                     continue
 
+                refs = [dbref for dbref in dbrefs
+                        if (collection, dbref) not in object_map]
+
                 if doc_type:
                     references = doc_type._get_db()[collection].find({'_id': {'$in': refs}})
                     for ref in references:
                         doc = doc_type._from_son(ref)
-                        object_map[doc.id] = doc
+                        object_map[(collection, doc.id)] = doc
                 else:
                     references = get_db()[collection].find({'_id': {'$in': refs}})
                     for ref in references:
@@ -154,7 +158,7 @@ class DeReference(object):
                                     for x in collection.split('_')))._from_son(ref)
                         else:
                             doc = doc_type._from_son(ref)
-                        object_map[doc.id] = doc
+                        object_map[(collection, doc.id)] = doc
         return object_map
 
     def _attach_objects(self, items, depth=0, instance=None, name=None):
@@ -180,7 +184,8 @@ class DeReference(object):
 
         if isinstance(items, (dict, SON)):
             if '_ref' in items:
-                return self.object_map.get(items['_ref'].id, items)
+                return self.object_map.get(
+                    (items['_ref'].collection, items['_ref'].id), items)
             elif '_cls' in items:
                 doc = get_document(items['_cls'])._from_son(items)
                 _cls = doc._data.pop('_cls', None)
@@ -216,9 +221,11 @@ class DeReference(object):
                 for field_name, field in v._fields.iteritems():
                     v = data[k]._data.get(field_name, None)
                     if isinstance(v, (DBRef)):
-                        data[k]._data[field_name] = self.object_map.get(v.id, v)
+                        data[k]._data[field_name] = self.object_map.get(
+                            (v.collection, v.id), v)
                     elif isinstance(v, (dict, SON)) and '_ref' in v:
-                        data[k]._data[field_name] = self.object_map.get(v['_ref'].id, v)
+                        data[k]._data[field_name] = self.object_map.get(
+                            (v['_ref'].collection , v['_ref'].id), v)
                     elif isinstance(v, (dict, list, tuple)) and depth <= self.max_depth:
                         item_name = "{0}.{1}.{2}".format(name, k, field_name)
                         data[k]._data[field_name] = self._attach_objects(v, depth, instance=instance, name=item_name)
@@ -226,7 +233,7 @@ class DeReference(object):
                 item_name = '%s.%s' % (name, k) if name else name
                 data[k] = self._attach_objects(v, depth - 1, instance=instance, name=item_name)
             elif hasattr(v, 'id'):
-                data[k] = self.object_map.get(v.id, v)
+                data[k] = self.object_map.get((v.collection, v.id), v)
 
         if instance and name:
             if is_list:
diff --git a/mongoengine/document.py b/mongoengine/document.py
index 791572a4..654d7a4c 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -1,4 +1,4 @@
-
+import warnings
 import pymongo
 import re
 
@@ -17,6 +17,7 @@ from mongoengine.base import (
     get_document
 )
 from mongoengine.errors import InvalidQueryError, InvalidDocumentError
+from mongoengine.python_support import IS_PYMONGO_3
 from mongoengine.queryset import (OperationError, NotUniqueError,
                                   QuerySet, transform)
 from mongoengine.connection import get_db, DEFAULT_CONNECTION_NAME
@@ -113,9 +114,11 @@ class Document(BaseDocument):
     specifying :attr:`max_documents` and :attr:`max_size` in the :attr:`meta`
     dictionary. :attr:`max_documents` is the maximum number of documents that
     is allowed to be stored in the collection, and :attr:`max_size` is the
-    maximum size of the collection in bytes. If :attr:`max_size` is not
+    maximum size of the collection in bytes. :attr:`max_size` is rounded up
+    to the next multiple of 256 by MongoDB internally and mongoengine before.
+    Use also a multiple of 256 to avoid confusions.  If :attr:`max_size` is not
     specified and :attr:`max_documents` is, :attr:`max_size` defaults to
-    10000000 bytes (10MB).
+    10485760 bytes (10MB).
 
     Indexes may be created by specifying :attr:`indexes` in the :attr:`meta`
     dictionary. The value should be a list of field names or tuples of field
@@ -136,7 +139,7 @@ class Document(BaseDocument):
     By default, any extra attribute existing in stored data but not declared
     in your model will raise a :class:`~mongoengine.FieldDoesNotExist` error.
     This can be disabled by setting :attr:`strict` to ``False``
-    in the :attr:`meta` dictionnary.
+    in the :attr:`meta` dictionary.
     """
 
     # The __metaclass__ attribute is removed by 2to3 when running with Python3
@@ -144,13 +147,15 @@ class Document(BaseDocument):
     my_metaclass = TopLevelDocumentMetaclass
     __metaclass__ = TopLevelDocumentMetaclass
 
-    __slots__ = ('__objects')
+    __slots__ = ('__objects',)
 
     def pk():
         """Primary key alias
         """
 
         def fget(self):
+            if 'id_field' not in self._meta:
+                return None
             return getattr(self, self._meta['id_field'])
 
         def fset(self, value):
@@ -171,10 +176,13 @@ class Document(BaseDocument):
             db = cls._get_db()
             collection_name = cls._get_collection_name()
             # Create collection as a capped collection if specified
-            if cls._meta['max_size'] or cls._meta['max_documents']:
+            if cls._meta.get('max_size') or cls._meta.get('max_documents'):
                 # Get max document limit and max byte size from meta
-                max_size = cls._meta['max_size'] or 10000000  # 10MB default
-                max_documents = cls._meta['max_documents']
+                max_size = cls._meta.get('max_size') or 10 * 2 ** 20  # 10MB default
+                max_documents = cls._meta.get('max_documents')
+                # Round up to next 256 bytes as MongoDB would do it to avoid exception
+                if max_size % 256:
+                    max_size = (max_size // 256 + 1) * 256
 
                 if collection_name in db.collection_names():
                     cls._collection = db[collection_name]
@@ -265,7 +273,8 @@ class Document(BaseDocument):
             to cascading saves.  Implies ``cascade=True``.
         :param _refs: A list of processed references used in cascading saves
         :param save_condition: only perform save if matching record in db
-            satisfies condition(s) (e.g., version number)
+            satisfies condition(s) (e.g. version number).
+            Raises :class:`OperationError` if the conditions are not satisfied
 
         .. versionchanged:: 0.5
             In existing documents it only saves changed fields using
@@ -283,6 +292,8 @@ class Document(BaseDocument):
         .. versionchanged:: 0.8.5
             Optional save_condition that only overwrites existing documents
             if the condition is satisfied in the current db record.
+        .. versionchanged:: 0.10
+            :class:`OperationError` exception raised if save_condition fails.
         """
         signals.pre_save.send(self.__class__, document=self)
 
@@ -347,6 +358,9 @@ class Document(BaseDocument):
                     upsert = save_condition is None
                     last_error = collection.update(select_dict, update_query,
                                                    upsert=upsert, **write_concern)
+                    if not upsert and last_error['nModified'] == 0:
+                        raise OperationError('Race condition preventing'
+                                             ' document update detected')
                     created = is_new_object(last_error)
 
             if cascade is None:
@@ -635,23 +649,51 @@ class Document(BaseDocument):
         db = cls._get_db()
         db.drop_collection(cls._get_collection_name())
 
+    @classmethod
+    def create_index(cls, keys, background=False, **kwargs):
+        """Creates the given indexes if required.
+
+        :param keys: a single index key or a list of index keys (to
+            construct a multi-field index); keys may be prefixed with a **+**
+            or a **-** to determine the index ordering
+        :param background: Allows index creation in the background
+        """
+        index_spec = cls._build_index_spec(keys)
+        index_spec = index_spec.copy()
+        fields = index_spec.pop('fields')
+        drop_dups = kwargs.get('drop_dups', False)
+        if IS_PYMONGO_3 and drop_dups:
+            msg = "drop_dups is deprecated and is removed when using PyMongo 3+."
+            warnings.warn(msg, DeprecationWarning)
+        elif not IS_PYMONGO_3:
+            index_spec['drop_dups'] = drop_dups
+        index_spec['background'] = background
+        index_spec.update(kwargs)
+
+        if IS_PYMONGO_3:
+            return cls._get_collection().create_index(fields, **index_spec)
+        else:
+            return cls._get_collection().ensure_index(fields, **index_spec)
+
     @classmethod
     def ensure_index(cls, key_or_list, drop_dups=False, background=False,
                      **kwargs):
-        """Ensure that the given indexes are in place.
+        """Ensure that the given indexes are in place. Deprecated in favour
+        of create_index.
 
         :param key_or_list: a single index key or a list of index keys (to
             construct a multi-field index); keys may be prefixed with a **+**
             or a **-** to determine the index ordering
+        :param background: Allows index creation in the background
+        :param drop_dups: Was removed/ignored with MongoDB >2.7.5. The value
+            will be removed if PyMongo3+ is used
         """
-        index_spec = cls._build_index_spec(key_or_list)
-        index_spec = index_spec.copy()
-        fields = index_spec.pop('fields')
-        index_spec['drop_dups'] = drop_dups
-        index_spec['background'] = background
-        index_spec.update(kwargs)
-
-        return cls._get_collection().ensure_index(fields, **index_spec)
+        if IS_PYMONGO_3 and drop_dups:
+            msg = "drop_dups is deprecated and is removed when using PyMongo 3+."
+            warnings.warn(msg, DeprecationWarning)
+        elif not IS_PYMONGO_3:
+            kwargs.update({'drop_dups': drop_dups})
+        return cls.create_index(key_or_list, background=background, **kwargs)
 
     @classmethod
     def ensure_indexes(cls):
@@ -666,6 +708,9 @@ class Document(BaseDocument):
         drop_dups = cls._meta.get('index_drop_dups', False)
         index_opts = cls._meta.get('index_opts') or {}
         index_cls = cls._meta.get('index_cls', True)
+        if IS_PYMONGO_3 and drop_dups:
+            msg = "drop_dups is deprecated and is removed when using PyMongo 3+."
+            warnings.warn(msg, DeprecationWarning)
 
         collection = cls._get_collection()
         # 746: when connection is via mongos, the read preference is not necessarily an indication that
@@ -694,8 +739,11 @@ class Document(BaseDocument):
                 if 'cls' in opts:
                     del opts['cls']
 
-                collection.ensure_index(fields, background=background,
-                                        drop_dups=drop_dups, **opts)
+                if IS_PYMONGO_3:
+                    collection.create_index(fields, background=background, **opts)
+                else:
+                    collection.ensure_index(fields, background=background,
+                                            drop_dups=drop_dups, **opts)
 
         # If _cls is being used (for polymorphism), it needs an index,
         # only if another index doesn't begin with _cls
@@ -707,8 +755,12 @@ class Document(BaseDocument):
             if 'cls' in index_opts:
                 del index_opts['cls']
 
-            collection.ensure_index('_cls', background=background,
-                                    **index_opts)
+            if IS_PYMONGO_3:
+                collection.create_index('_cls', background=background,
+                                        **index_opts)
+            else:
+                collection.ensure_index('_cls', background=background,
+                                        **index_opts)
 
     @classmethod
     def list_indexes(cls, go_up=True, go_down=True):
diff --git a/mongoengine/fields.py b/mongoengine/fields.py
index 53d4ac95..c27d02b2 100644
--- a/mongoengine/fields.py
+++ b/mongoengine/fields.py
@@ -119,22 +119,31 @@ class URLField(StringField):
     """
 
     _URL_REGEX = re.compile(
-        r'^(?:http|ftp)s?://'  # http:// or https://
-        # domain...
-        r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}\.?)|'
+        r'^(?:[a-z0-9\.\-]*)://'  # scheme is validated separately
+        r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}(?<!-)\.?)|'  # domain...
         r'localhost|'  # localhost...
-        r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})'  # ...or ip
+        r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}|'  # ...or ipv4
+        r'\[?[A-F0-9]*:[A-F0-9:]+\]?)'  # ...or ipv6
         r'(?::\d+)?'  # optional port
         r'(?:/?|[/?]\S+)$', re.IGNORECASE)
+    _URL_SCHEMES = ['http', 'https', 'ftp', 'ftps']
 
-    def __init__(self, verify_exists=False, url_regex=None, **kwargs):
+    def __init__(self, verify_exists=False, url_regex=None, schemes=None, **kwargs):
         self.verify_exists = verify_exists
         self.url_regex = url_regex or self._URL_REGEX
+        self.schemes = schemes or self._URL_SCHEMES
         super(URLField, self).__init__(**kwargs)
 
     def validate(self, value):
+        # Check first if the scheme is valid
+        scheme = value.split('://')[0].lower()
+        if scheme not in self.schemes:
+            self.error('Invalid scheme {} in URL: {}'.format(scheme, value))
+            return
+
+        # Then check full URL
         if not self.url_regex.match(value):
-            self.error('Invalid URL: %s' % value)
+            self.error('Invalid URL: {}'.format(value))
             return
 
         if self.verify_exists:
@@ -162,7 +171,7 @@ class EmailField(StringField):
         # quoted-string
         r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*"'
         # domain (max length of an ICAAN TLD is 22 characters)
-        r')@(?:[A-Z0-9](?:[A-Z0-9-]{0,253}[A-Z0-9])?\.)+[A-Z]{2,22}$', re.IGNORECASE
+        r')@(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}|[A-Z0-9-]{2,}(?<!-))$', re.IGNORECASE
     )
 
     def validate(self, value):
@@ -546,7 +555,7 @@ class EmbeddedDocumentField(BaseField):
 
     def to_python(self, value):
         if not isinstance(value, self.document_type):
-            return self.document_type._from_son(value)
+            return self.document_type._from_son(value, _auto_dereference=self._auto_dereference)
         return value
 
     def to_mongo(self, value, use_db_field=True, fields=[]):
@@ -1004,6 +1013,7 @@ class CachedReferenceField(BaseField):
 
     """
     A referencefield with cache fields to purpose pseudo-joins
+    
     .. versionadded:: 0.9
     """
 
@@ -1674,12 +1684,21 @@ class SequenceField(BaseField):
              cluster of machines, it is easier to create an object ID than have
              global, uniformly increasing sequence numbers.
 
+    :param collection_name:  Name of the counter collection (default 'mongoengine.counters')
+    :param sequence_name: Name of the sequence in the collection (default 'ClassName.counter')
+    :param value_decorator: Any callable to use as a counter (default int)
+        
     Use any callable as `value_decorator` to transform calculated counter into
     any value suitable for your needs, e.g. string or hexadecimal
     representation of the default integer counter value.
-
+    
+    .. note::
+    
+        In case the counter is defined in the abstract document, it will be 
+        common to all inherited documents and the default sequence name will 
+        be the class name of the abstract document.
+    
     .. versionadded:: 0.5
-
     .. versionchanged:: 0.8 added `value_decorator`
     """
 
@@ -1694,7 +1713,7 @@ class SequenceField(BaseField):
         self.sequence_name = sequence_name
         self.value_decorator = (callable(value_decorator) and
                                 value_decorator or self.VALUE_DECORATOR)
-        return super(SequenceField, self).__init__(*args, **kwargs)
+        super(SequenceField, self).__init__(*args, **kwargs)
 
     def generate(self):
         """
@@ -1740,7 +1759,7 @@ class SequenceField(BaseField):
         if self.sequence_name:
             return self.sequence_name
         owner = self.owner_document
-        if issubclass(owner, Document):
+        if issubclass(owner, Document) and not owner._meta.get('abstract'):
             return owner._get_collection_name()
         else:
             return ''.join('_%s' % c if c.isupper() else c
diff --git a/mongoengine/queryset/base.py b/mongoengine/queryset/base.py
index 89eb9afa..c3abd46a 100644
--- a/mongoengine/queryset/base.py
+++ b/mongoengine/queryset/base.py
@@ -258,54 +258,6 @@ class BaseQuerySet(object):
         """
         return self._document(**kwargs).save()
 
-    def get_or_create(self, write_concern=None, auto_save=True,
-                      *q_objs, **query):
-        """Retrieve unique object or create, if it doesn't exist. Returns a
-        tuple of ``(object, created)``, where ``object`` is the retrieved or
-        created object and ``created`` is a boolean specifying whether a new
-        object was created. Raises
-        :class:`~mongoengine.queryset.MultipleObjectsReturned` or
-        `DocumentName.MultipleObjectsReturned` if multiple results are found.
-        A new document will be created if the document doesn't exists; a
-        dictionary of default values for the new document may be provided as a
-        keyword argument called :attr:`defaults`.
-
-        .. note:: This requires two separate operations and therefore a
-            race condition exists.  Because there are no transactions in
-            mongoDB other approaches should be investigated, to ensure you
-            don't accidentally duplicate data when using this method.  This is
-            now scheduled to be removed before 1.0
-
-        :param write_concern: optional extra keyword arguments used if we
-            have to create a new document.
-            Passes any write_concern onto :meth:`~mongoengine.Document.save`
-
-        :param auto_save: if the object is to be saved automatically if
-            not found.
-
-        .. deprecated:: 0.8
-        .. versionchanged:: 0.6 - added `auto_save`
-        .. versionadded:: 0.3
-        """
-        msg = ("get_or_create is scheduled to be deprecated.  The approach is "
-               "flawed without transactions. Upserts should be preferred.")
-        warnings.warn(msg, DeprecationWarning)
-
-        defaults = query.get('defaults', {})
-        if 'defaults' in query:
-            del query['defaults']
-
-        try:
-            doc = self.get(*q_objs, **query)
-            return doc, False
-        except self._document.DoesNotExist:
-            query.update(defaults)
-            doc = self._document(**query)
-
-            if auto_save:
-                doc.save(write_concern=write_concern)
-            return doc, True
-
     def first(self):
         """Retrieve the first object matching the query.
         """
@@ -1296,6 +1248,27 @@ class BaseQuerySet(object):
         else:
             return 0
 
+    def aggregate_sum(self, field):
+        """Sum over the values of the specified field.
+
+        :param field: the field to sum over; use dot-notation to refer to
+            embedded document fields
+
+        This method is more performant than the regular `sum`, because it uses
+        the aggregation framework instead of map-reduce.
+        """
+        result = self._document._get_collection().aggregate([
+            { '$match': self._query },
+            { '$group': { '_id': 'sum', 'total': { '$sum': '$' + field } } }
+        ])
+        if IS_PYMONGO_3:
+            result = list(result)
+        else:
+            result = result.get('result')
+        if result:
+            return result[0]['total']
+        return 0
+
     def average(self, field):
         """Average over the values of the specified field.
 
@@ -1351,6 +1324,27 @@ class BaseQuerySet(object):
         else:
             return 0
 
+    def aggregate_average(self, field):
+        """Average over the values of the specified field.
+
+        :param field: the field to average over; use dot-notation to refer to
+            embedded document fields
+
+        This method is more performant than the regular `average`, because it
+        uses the aggregation framework instead of map-reduce.
+        """
+        result = self._document._get_collection().aggregate([
+            { '$match': self._query },
+            { '$group': { '_id': 'avg', 'total': { '$avg': '$' + field } } }
+        ])
+        if IS_PYMONGO_3:
+            result = list(result)
+        else:
+            result = result.get('result')
+        if result:
+            return result[0]['total']
+        return 0
+
     def item_frequencies(self, field, normalize=False, map_reduce=True):
         """Returns a dictionary of all items present in a field across
         the whole queried set of documents, and their corresponding frequency.
diff --git a/mongoengine/queryset/transform.py b/mongoengine/queryset/transform.py
index c43c4b40..f6cfa87e 100644
--- a/mongoengine/queryset/transform.py
+++ b/mongoengine/queryset/transform.py
@@ -44,7 +44,7 @@ def query(_doc_cls=None, _field_operation=False, **query):
         if len(parts) > 1 and parts[-1] in MATCH_OPERATORS:
             op = parts.pop()
 
-        #if user escape field name by __
+        # if user escape field name by __
         if len(parts) > 1 and parts[-1] == "":
             parts.pop()
 
diff --git a/tests/document/indexes.py b/tests/document/indexes.py
index d43b22e5..dcc71e5b 100644
--- a/tests/document/indexes.py
+++ b/tests/document/indexes.py
@@ -275,6 +275,60 @@ class IndexesTest(unittest.TestCase):
         info = [value['key'] for key, value in info.iteritems()]
         self.assertTrue([('current.location.point', '2d')] in info)
 
+    def test_explicit_geosphere_index(self):
+        """Ensure that geosphere indexes work when created via meta[indexes]
+        """
+        class Place(Document):
+            location = DictField()
+            meta = {
+                'allow_inheritance': True,
+                'indexes': [
+                    '(location.point',
+                ]
+            }
+
+        self.assertEqual([{'fields': [('location.point', '2dsphere')]}],
+                         Place._meta['index_specs'])
+
+        Place.ensure_indexes()
+        info = Place._get_collection().index_information()
+        info = [value['key'] for key, value in info.iteritems()]
+        self.assertTrue([('location.point', '2dsphere')] in info)
+
+    def test_explicit_geohaystack_index(self):
+        """Ensure that geohaystack indexes work when created via meta[indexes]
+        """
+        raise SkipTest('GeoHaystack index creation is not supported for now'
+                       'from meta, as it requires a bucketSize parameter.')
+
+        class Place(Document):
+            location = DictField()
+            name = StringField()
+            meta = {
+                'indexes': [
+                    (')location.point', 'name')
+                ]
+            }
+        self.assertEqual([{'fields': [('location.point', 'geoHaystack'), ('name', 1)]}],
+                         Place._meta['index_specs'])
+
+        Place.ensure_indexes()
+        info = Place._get_collection().index_information()
+        info = [value['key'] for key, value in info.iteritems()]
+        self.assertTrue([('location.point', 'geoHaystack')] in info)
+
+    def test_create_geohaystack_index(self):
+        """Ensure that geohaystack indexes can be created
+        """
+        class Place(Document):
+            location = DictField()
+            name = StringField()
+
+        Place.create_index({'fields': (')location.point', 'name')}, bucketSize=10)
+        info = Place._get_collection().index_information()
+        info = [value['key'] for key, value in info.iteritems()]
+        self.assertTrue([('location.point', 'geoHaystack'), ('name', 1)] in info)
+
     def test_dictionary_indexes(self):
         """Ensure that indexes are used when meta[indexes] contains
         dictionaries instead of lists.
@@ -822,6 +876,18 @@ class IndexesTest(unittest.TestCase):
         key = indexes["title_text"]["key"]
         self.assertTrue(('_fts', 'text') in key)
 
+    def test_hashed_indexes(self):
+
+        class Book(Document):
+            ref_id = StringField()
+            meta = {
+                "indexes": ["#ref_id"],
+            }
+
+        indexes = Book.objects._collection.index_information()
+        self.assertTrue("ref_id_hashed" in indexes)
+        self.assertTrue(('ref_id', 'hashed') in indexes["ref_id_hashed"]["key"])
+
     def test_indexes_after_database_drop(self):
         """
         Test to ensure that indexes are re-created on a collection even
@@ -909,6 +975,30 @@ class IndexesTest(unittest.TestCase):
             }
         })
 
+    def test_compound_index_underscore_cls_not_overwritten(self):
+        """
+        Test that the compound index doesn't get another _cls when it is specified
+        """
+        class TestDoc(Document):
+            shard_1 = StringField()
+            txt_1 = StringField()
+
+            meta = {
+                'collection': 'test',
+                'allow_inheritance': True,
+                'sparse': True,
+                'shard_key': 'shard_1',
+                'indexes': [
+                    ('shard_1', '_cls', 'txt_1'),
+                ]
+            }
+
+        TestDoc.drop_collection()
+        TestDoc.ensure_indexes()
+
+        index_info = TestDoc._get_collection().index_information()
+        self.assertTrue('shard_1_1__cls_1_txt_1_1' in index_info)
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/document/inheritance.py b/tests/document/inheritance.py
index e8347054..7673a103 100644
--- a/tests/document/inheritance.py
+++ b/tests/document/inheritance.py
@@ -307,6 +307,69 @@ class InheritanceTest(unittest.TestCase):
         doc = Animal(name='dog')
         self.assertFalse('_cls' in doc.to_mongo())
 
+    def test_abstract_handle_ids_in_metaclass_properly(self):
+
+        class City(Document):
+            continent = StringField()
+            meta = {'abstract': True,
+                    'allow_inheritance': False}
+
+        class EuropeanCity(City):
+            name = StringField()
+
+        berlin = EuropeanCity(name='Berlin', continent='Europe')
+        self.assertEqual(len(berlin._db_field_map), len(berlin._fields_ordered))
+        self.assertEqual(len(berlin._reverse_db_field_map), len(berlin._fields_ordered))
+        self.assertEqual(len(berlin._fields_ordered), 3)
+        self.assertEqual(berlin._fields_ordered[0], 'id')
+
+    def test_auto_id_not_set_if_specific_in_parent_class(self):
+
+        class City(Document):
+            continent = StringField()
+            city_id = IntField(primary_key=True)
+            meta = {'abstract': True,
+                    'allow_inheritance': False}
+
+        class EuropeanCity(City):
+            name = StringField()
+
+        berlin = EuropeanCity(name='Berlin', continent='Europe')
+        self.assertEqual(len(berlin._db_field_map), len(berlin._fields_ordered))
+        self.assertEqual(len(berlin._reverse_db_field_map), len(berlin._fields_ordered))
+        self.assertEqual(len(berlin._fields_ordered), 3)
+        self.assertEqual(berlin._fields_ordered[0], 'city_id')
+
+    def test_auto_id_vs_non_pk_id_field(self):
+
+        class City(Document):
+            continent = StringField()
+            id = IntField()
+            meta = {'abstract': True,
+                    'allow_inheritance': False}
+
+        class EuropeanCity(City):
+            name = StringField()
+
+        berlin = EuropeanCity(name='Berlin', continent='Europe')
+        self.assertEqual(len(berlin._db_field_map), len(berlin._fields_ordered))
+        self.assertEqual(len(berlin._reverse_db_field_map), len(berlin._fields_ordered))
+        self.assertEqual(len(berlin._fields_ordered), 4)
+        self.assertEqual(berlin._fields_ordered[0], 'auto_id_0')
+        berlin.save()
+        self.assertEqual(berlin.pk, berlin.auto_id_0)
+
+    def test_abstract_document_creation_does_not_fail(self):
+
+        class City(Document):
+            continent = StringField()
+            meta = {'abstract': True,
+                    'allow_inheritance': False}
+        bkk = City(continent='asia')
+        self.assertEqual(None, bkk.pk)
+        # TODO: expected error? Shouldn't we create a new error type?
+        self.assertRaises(KeyError, lambda: setattr(bkk, 'pk', 1))
+
     def test_allow_inheritance_embedded_document(self):
         """Ensure embedded documents respect inheritance
         """
diff --git a/tests/document/instance.py b/tests/document/instance.py
index 2cfdef65..fceec02f 100644
--- a/tests/document/instance.py
+++ b/tests/document/instance.py
@@ -88,7 +88,7 @@ class InstanceTest(unittest.TestCase):
         options = Log.objects._collection.options()
         self.assertEqual(options['capped'], True)
         self.assertEqual(options['max'], 10)
-        self.assertTrue(options['size'] >= 4096)
+        self.assertEqual(options['size'], 4096)
 
         # Check that the document cannot be redefined with different options
         def recreate_log_document():
@@ -103,6 +103,69 @@ class InstanceTest(unittest.TestCase):
 
         Log.drop_collection()
 
+    def test_capped_collection_default(self):
+        """Ensure that capped collections defaults work properly.
+        """
+        class Log(Document):
+            date = DateTimeField(default=datetime.now)
+            meta = {
+                'max_documents': 10,
+            }
+
+        Log.drop_collection()
+
+        # Create a doc to create the collection
+        Log().save()
+
+        options = Log.objects._collection.options()
+        self.assertEqual(options['capped'], True)
+        self.assertEqual(options['max'], 10)
+        self.assertEqual(options['size'], 10 * 2**20)
+
+        # Check that the document with default value can be recreated
+        def recreate_log_document():
+            class Log(Document):
+                date = DateTimeField(default=datetime.now)
+                meta = {
+                    'max_documents': 10,
+                }
+            # Create the collection by accessing Document.objects
+            Log.objects
+        recreate_log_document()
+        Log.drop_collection()
+
+    def test_capped_collection_no_max_size_problems(self):
+        """Ensure that capped collections with odd max_size work properly.
+        MongoDB rounds up max_size to next multiple of 256, recreating a doc
+        with the same spec failed in mongoengine <0.10
+        """
+        class Log(Document):
+            date = DateTimeField(default=datetime.now)
+            meta = {
+                'max_size': 10000,
+            }
+
+        Log.drop_collection()
+
+        # Create a doc to create the collection
+        Log().save()
+
+        options = Log.objects._collection.options()
+        self.assertEqual(options['capped'], True)
+        self.assertTrue(options['size'] >= 10000)
+
+        # Check that the document with odd max_size value can be recreated
+        def recreate_log_document():
+            class Log(Document):
+                date = DateTimeField(default=datetime.now)
+                meta = {
+                    'max_size': 10000,
+                }
+            # Create the collection by accessing Document.objects
+            Log.objects
+        recreate_log_document()
+        Log.drop_collection()
+
     def test_repr(self):
         """Ensure that unicode representation works
         """
@@ -954,11 +1017,12 @@ class InstanceTest(unittest.TestCase):
         self.assertEqual(w1.save_id, UUID(1))
         self.assertEqual(w1.count, 0)
 
-        # mismatch in save_condition prevents save
+        # mismatch in save_condition prevents save and raise exception
         flip(w1)
         self.assertTrue(w1.toggle)
         self.assertEqual(w1.count, 1)
-        w1.save(save_condition={'save_id': UUID(42)})
+        self.assertRaises(OperationError,
+            w1.save, save_condition={'save_id': UUID(42)})
         w1.reload()
         self.assertFalse(w1.toggle)
         self.assertEqual(w1.count, 0)
@@ -986,7 +1050,8 @@ class InstanceTest(unittest.TestCase):
         self.assertEqual(w1.count, 2)
         flip(w2)
         flip(w2)
-        w2.save(save_condition={'save_id': old_id})
+        self.assertRaises(OperationError,
+            w2.save, save_condition={'save_id': old_id})
         w2.reload()
         self.assertFalse(w2.toggle)
         self.assertEqual(w2.count, 2)
@@ -998,7 +1063,8 @@ class InstanceTest(unittest.TestCase):
         self.assertTrue(w1.toggle)
         self.assertEqual(w1.count, 3)
         flip(w1)
-        w1.save(save_condition={'count__gte': w1.count})
+        self.assertRaises(OperationError,
+            w1.save, save_condition={'count__gte': w1.count})
         w1.reload()
         self.assertTrue(w1.toggle)
         self.assertEqual(w1.count, 3)
diff --git a/tests/fields/fields.py b/tests/fields/fields.py
index fd083c73..35e3ca39 100644
--- a/tests/fields/fields.py
+++ b/tests/fields/fields.py
@@ -39,6 +39,7 @@ class FieldTest(unittest.TestCase):
     def tearDown(self):
         self.db.drop_collection('fs.files')
         self.db.drop_collection('fs.chunks')
+        self.db.drop_collection('mongoengine.counters')
 
     def test_default_values_nothing_set(self):
         """Ensure that default field values are used when creating a document.
@@ -341,6 +342,23 @@ class FieldTest(unittest.TestCase):
         link.url = 'http://www.google.com:8080'
         link.validate()
 
+    def test_url_scheme_validation(self):
+        """Ensure that URLFields validate urls with specific schemes properly.
+        """
+        class Link(Document):
+            url = URLField()
+
+        class SchemeLink(Document):
+            url = URLField(schemes=['ws', 'irc'])
+
+        link = Link()
+        link.url = 'ws://google.com'
+        self.assertRaises(ValidationError, link.validate)
+
+        scheme_link = SchemeLink()
+        scheme_link.url = 'ws://google.com'
+        scheme_link.validate()
+
     def test_int_validation(self):
         """Ensure that invalid values cannot be assigned to int fields.
         """
@@ -2134,9 +2152,7 @@ class FieldTest(unittest.TestCase):
         obj = Product.objects(company=None).first()
         self.assertEqual(obj, me)
 
-        obj, created = Product.objects.get_or_create(company=None)
-
-        self.assertEqual(created, False)
+        obj = Product.objects.get(company=None)
         self.assertEqual(obj, me)
 
     def test_reference_query_conversion(self):
@@ -2954,6 +2970,57 @@ class FieldTest(unittest.TestCase):
         self.assertEqual(1, post.comments[0].id)
         self.assertEqual(2, post.comments[1].id)
 
+    def test_inherited_sequencefield(self):
+        class Base(Document):
+            name = StringField()
+            counter = SequenceField()
+            meta = {'abstract': True}
+
+        class Foo(Base):
+            pass
+
+        class Bar(Base):
+            pass
+
+        bar = Bar(name='Bar')
+        bar.save()
+
+        foo = Foo(name='Foo')
+        foo.save()
+
+        self.assertTrue('base.counter' in
+                        self.db['mongoengine.counters'].find().distinct('_id'))
+        self.assertFalse(('foo.counter' or 'bar.counter') in
+                         self.db['mongoengine.counters'].find().distinct('_id'))
+        self.assertNotEqual(foo.counter, bar.counter)
+        self.assertEqual(foo._fields['counter'].owner_document, Base)
+        self.assertEqual(bar._fields['counter'].owner_document, Base)
+
+    def test_no_inherited_sequencefield(self):
+        class Base(Document):
+            name = StringField()
+            meta = {'abstract': True}
+
+        class Foo(Base):
+            counter = SequenceField()
+
+        class Bar(Base):
+            counter = SequenceField()
+
+        bar = Bar(name='Bar')
+        bar.save()
+
+        foo = Foo(name='Foo')
+        foo.save()
+
+        self.assertFalse('base.counter' in
+                         self.db['mongoengine.counters'].find().distinct('_id'))
+        self.assertTrue(('foo.counter' and 'bar.counter') in
+                         self.db['mongoengine.counters'].find().distinct('_id'))
+        self.assertEqual(foo.counter, bar.counter)
+        self.assertEqual(foo._fields['counter'].owner_document, Foo)
+        self.assertEqual(bar._fields['counter'].owner_document, Bar)
+
     def test_generic_embedded_document(self):
         class Car(EmbeddedDocument):
             name = StringField()
@@ -3088,7 +3155,6 @@ class FieldTest(unittest.TestCase):
         self.assertTrue(user.validate() is None)
 
         user = User(email=("Kofq@rhom0e4klgauOhpbpNdogawnyIKvQS0wk2mjqrgGQ5S"
-                           "ucictfqpdkK9iS1zeFw8sg7s7cwAF7suIfUfeyueLpfosjn3"
                            "aJIazqqWkm7.net"))
         self.assertTrue(user.validate() is None)
 
diff --git a/tests/queryset/queryset.py b/tests/queryset/queryset.py
index 65d84305..d4348678 100644
--- a/tests/queryset/queryset.py
+++ b/tests/queryset/queryset.py
@@ -13,7 +13,7 @@ import pymongo
 from pymongo.errors import ConfigurationError
 from pymongo.read_preferences import ReadPreference
 
-from bson import ObjectId
+from bson import ObjectId, DBRef
 
 from mongoengine import *
 from mongoengine.connection import get_connection, get_db
@@ -340,8 +340,7 @@ class QuerySetTest(unittest.TestCase):
 
         write_concern = {"fsync": True}
 
-        author, created = self.Person.objects.get_or_create(
-            name='Test User', write_concern=write_concern)
+        author = self.Person.objects.create(name='Test User')
         author.save(write_concern=write_concern)
 
         result = self.Person.objects.update(
@@ -630,6 +629,40 @@ class QuerySetTest(unittest.TestCase):
         self.assertRaises(ValidationError, Doc.objects().update, dt_f="datetime", upsert=True)
         self.assertRaises(ValidationError, Doc.objects().update, ed_f__str_f=1, upsert=True)
 
+    def test_update_related_models( self ):
+            class TestPerson( Document ):
+                name = StringField()
+
+            class TestOrganization( Document ):
+                name = StringField()
+                owner = ReferenceField( TestPerson )
+
+            TestPerson.drop_collection()
+            TestOrganization.drop_collection()
+
+            p = TestPerson( name='p1' )
+            p.save()
+            o = TestOrganization( name='o1' )
+            o.save()
+
+            o.owner = p
+            p.name = 'p2'
+
+            self.assertEqual( o._get_changed_fields(), [ 'owner' ] )
+            self.assertEqual( p._get_changed_fields(), [ 'name' ] )
+
+            o.save()
+
+            self.assertEqual( o._get_changed_fields(), [] )
+            self.assertEqual( p._get_changed_fields(), [ 'name' ] ) # Fails; it's empty
+
+            # This will do NOTHING at all, even though we changed the name
+            p.save()
+
+            p.reload()
+
+            self.assertEqual( p.name, 'p2' ) # Fails; it's still `p1`
+
     def test_upsert(self):
         self.Person.drop_collection()
 
@@ -659,37 +692,42 @@ class QuerySetTest(unittest.TestCase):
         self.assertEqual("Bob", bob.name)
         self.assertEqual(30, bob.age)
 
-    def test_get_or_create(self):
-        """Ensure that ``get_or_create`` returns one result or creates a new
-        document.
-        """
-        person1 = self.Person(name="User A", age=20)
-        person1.save()
-        person2 = self.Person(name="User B", age=30)
-        person2.save()
+    def test_save_and_only_on_fields_with_default(self):
+        class Embed(EmbeddedDocument):
+            field = IntField()
 
-        # Retrieve the first person from the database
-        self.assertRaises(MultipleObjectsReturned,
-                          self.Person.objects.get_or_create)
-        self.assertRaises(self.Person.MultipleObjectsReturned,
-                          self.Person.objects.get_or_create)
+        class B(Document):
+            meta = {'collection': 'b'}
 
-        # Use a query to filter the people found to just person2
-        person, created = self.Person.objects.get_or_create(age=30)
-        self.assertEqual(person.name, "User B")
-        self.assertEqual(created, False)
+            field = IntField(default=1)
+            embed = EmbeddedDocumentField(Embed, default=Embed)
+            embed_no_default = EmbeddedDocumentField(Embed)
 
-        person, created = self.Person.objects.get_or_create(age__lt=30)
-        self.assertEqual(person.name, "User A")
-        self.assertEqual(created, False)
+        # Creating {field : 2, embed : {field: 2}, embed_no_default: {field: 2}}
+        val = 2
+        embed = Embed()
+        embed.field = val
+        record = B()
+        record.field = val
+        record.embed = embed
+        record.embed_no_default = embed
+        record.save()
 
-        # Try retrieving when no objects exists - new doc should be created
-        kwargs = dict(age=50, defaults={'name': 'User C'})
-        person, created = self.Person.objects.get_or_create(**kwargs)
-        self.assertEqual(created, True)
+        # Checking it was saved correctly
+        record.reload()
+        self.assertEqual(record.field, 2)
+        self.assertEqual(record.embed_no_default.field, 2)
+        self.assertEqual(record.embed.field, 2)
 
-        person = self.Person.objects.get(age=50)
-        self.assertEqual(person.name, "User C")
+        # Request only the _id field and save
+        clone = B.objects().only('id').first()
+        clone.save()
+
+        # Reload the record and see that the embed data is not lost
+        record.reload()
+        self.assertEqual(record.field, 2)
+        self.assertEqual(record.embed_no_default.field, 2)
+        self.assertEqual(record.embed.field, 2)
 
     def test_bulk_insert(self):
         """Ensure that bulk insert works
@@ -2668,26 +2706,58 @@ class QuerySetTest(unittest.TestCase):
 
         avg = float(sum(ages)) / (len(ages) + 1)  # take into account the 0
         self.assertAlmostEqual(int(self.Person.objects.average('age')), avg)
+        self.assertAlmostEqual(
+            int(self.Person.objects.aggregate_average('age')), avg
+        )
 
         self.Person(name='ageless person').save()
         self.assertEqual(int(self.Person.objects.average('age')), avg)
+        self.assertEqual(
+            int(self.Person.objects.aggregate_average('age')), avg
+        )
 
         # dot notation
         self.Person(
             name='person meta', person_meta=self.PersonMeta(weight=0)).save()
         self.assertAlmostEqual(
             int(self.Person.objects.average('person_meta.weight')), 0)
+        self.assertAlmostEqual(
+            int(self.Person.objects.aggregate_average('person_meta.weight')),
+            0
+        )
 
         for i, weight in enumerate(ages):
             self.Person(
                 name='test meta%i', person_meta=self.PersonMeta(weight=weight)).save()
 
         self.assertAlmostEqual(
-            int(self.Person.objects.average('person_meta.weight')), avg)
+            int(self.Person.objects.average('person_meta.weight')), avg
+        )
+        self.assertAlmostEqual(
+            int(self.Person.objects.aggregate_average('person_meta.weight')),
+            avg
+        )
 
         self.Person(name='test meta none').save()
         self.assertEqual(
-            int(self.Person.objects.average('person_meta.weight')), avg)
+            int(self.Person.objects.average('person_meta.weight')), avg
+        )
+        self.assertEqual(
+            int(self.Person.objects.aggregate_average('person_meta.weight')),
+            avg
+        )
+
+        # test summing over a filtered queryset
+        over_50 = [a for a in ages if a >= 50]
+        avg = float(sum(over_50)) / len(over_50)
+        self.assertEqual(
+            self.Person.objects.filter(age__gte=50).average('age'),
+            avg
+        )
+        self.assertEqual(
+            self.Person.objects.filter(age__gte=50).aggregate_average('age'),
+            avg
+        )
 
     def test_sum(self):
         """Ensure that field can be summed over correctly.
@@ -2696,20 +2766,44 @@ class QuerySetTest(unittest.TestCase):
         for i, age in enumerate(ages):
             self.Person(name='test%s' % i, age=age).save()
 
-        self.assertEqual(int(self.Person.objects.sum('age')), sum(ages))
+        self.assertEqual(self.Person.objects.sum('age'), sum(ages))
+        self.assertEqual(
+            self.Person.objects.aggregate_sum('age'), sum(ages)
+        )
 
         self.Person(name='ageless person').save()
-        self.assertEqual(int(self.Person.objects.sum('age')), sum(ages))
+        self.assertEqual(self.Person.objects.sum('age'), sum(ages))
+        self.assertEqual(
+            self.Person.objects.aggregate_sum('age'), sum(ages)
+        )
 
         for i, age in enumerate(ages):
             self.Person(name='test meta%s' %
                         i, person_meta=self.PersonMeta(weight=age)).save()
 
         self.assertEqual(
-            int(self.Person.objects.sum('person_meta.weight')), sum(ages))
+            self.Person.objects.sum('person_meta.weight'), sum(ages)
+        )
+        self.assertEqual(
+            self.Person.objects.aggregate_sum('person_meta.weight'),
+            sum(ages)
+        )
 
         self.Person(name='weightless person').save()
-        self.assertEqual(int(self.Person.objects.sum('age')), sum(ages))
+        self.assertEqual(self.Person.objects.sum('age'), sum(ages))
+        self.assertEqual(
+            self.Person.objects.aggregate_sum('age'), sum(ages)
+        )
+
+        # test summing over a filtered queryset
+        self.assertEqual(
+            self.Person.objects.filter(age__gte=50).sum('age'),
+            sum([a for a in ages if a >= 50])
+        )
+        self.assertEqual(
+            self.Person.objects.filter(age__gte=50).aggregate_sum('age'),
+            sum([a for a in ages if a >= 50])
+        )
 
     def test_embedded_average(self):
         class Pay(EmbeddedDocument):
@@ -3655,11 +3749,9 @@ class QuerySetTest(unittest.TestCase):
     def test_scalar(self):
 
         class Organization(Document):
-            id = ObjectIdField('_id')
             name = StringField()
 
         class User(Document):
-            id = ObjectIdField('_id')
             name = StringField()
             organization = ObjectIdField()
 
@@ -4185,6 +4277,41 @@ class QuerySetTest(unittest.TestCase):
                                     Organization))
         self.assertTrue(isinstance(qs.first().organization, Organization))
 
+    def test_no_dereference_embedded_doc(self):
+
+        class User(Document):
+            name = StringField()
+
+        class Member(EmbeddedDocument):
+            name = StringField()
+            user = ReferenceField(User)
+
+        class Organization(Document):
+            name = StringField()
+            members = ListField(EmbeddedDocumentField(Member))
+            ceo = ReferenceField(User)
+            member = EmbeddedDocumentField(Member)
+            admin = ListField(ReferenceField(User))
+
+        Organization.drop_collection()
+        User.drop_collection()
+
+        user = User(name="Flash")
+        user.save()
+
+        member = Member(name="Flash", user=user)
+
+        company = Organization(name="Mongo Inc", ceo=user, member=member)
+        company.admin.append(user)
+        company.members.append(member)
+        company.save()
+
+        result = Organization.objects().no_dereference().first()
+
+        self.assertTrue(isinstance(result.admin[0], (DBRef, ObjectId)))
+        self.assertTrue(isinstance(result.member.user, (DBRef, ObjectId)))
+        self.assertTrue(isinstance(result.members[0].user, (DBRef, ObjectId)))
+
     def test_cached_queryset(self):
         class Person(Document):
             name = StringField()
@@ -4622,6 +4749,13 @@ class QuerySetTest(unittest.TestCase):
         self.assertEquals(Animal.objects(folded_ears=True).count(), 1)
         self.assertEquals(Animal.objects(whiskers_length=5.1).count(), 1)
 
+    def test_loop_via_invalid_id_does_not_crash(self):
+        class Person(Document):
+            name = StringField()
+        Person.objects.delete()
+        Person._get_collection().update({"name": "a"}, {"$set": {"_id": ""}}, upsert=True)
+        for p in Person.objects():
+            self.assertEqual(p.name, 'a')
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/queryset/transform.py b/tests/queryset/transform.py
index 77d3593c..a543317a 100644
--- a/tests/queryset/transform.py
+++ b/tests/queryset/transform.py
@@ -224,6 +224,15 @@ class TransformTest(unittest.TestCase):
         self.assertEqual(1, Doc.objects(item__type__="axe").count())
         self.assertEqual(1, Doc.objects(item__name__="Heroic axe").count())
 
+    def test_understandable_error_raised(self):
+        class Event(Document):
+            title = StringField()
+            location = GeoPointField()
+
+        box = [(35.0, -125.0), (40.0, -100.0)]
+        # I *meant* to execute location__within_box=box
+        events = Event.objects(location__within=box)
+        self.assertRaises(InvalidQueryError, lambda: events.count())
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/test_dereference.py b/tests/test_dereference.py
index 2115b45a..e1ae3740 100644
--- a/tests/test_dereference.py
+++ b/tests/test_dereference.py
@@ -1026,6 +1026,43 @@ class FieldTest(unittest.TestCase):
         self.assertEqual(type(foo.bar), Bar)
         self.assertEqual(type(foo.baz), Baz)
 
+
+    def test_document_reload_reference_integrity(self):
+        """
+        Ensure reloading a document with multiple similar id
+        in different collections doesn't mix them.
+        """
+        class Topic(Document):
+            id = IntField(primary_key=True)
+        class User(Document):
+            id = IntField(primary_key=True)
+            name = StringField()
+        class Message(Document):
+            id = IntField(primary_key=True)
+            topic = ReferenceField(Topic)
+            author = ReferenceField(User)
+
+        Topic.drop_collection()
+        User.drop_collection()
+        Message.drop_collection()
+
+        # All objects share the same id, but each in a different collection
+        topic = Topic(id=1).save()
+        user = User(id=1, name='user-name').save()
+        Message(id=1, topic=topic, author=user).save()
+
+        concurrent_change_user = User.objects.get(id=1)
+        concurrent_change_user.name = 'new-name'
+        concurrent_change_user.save()
+        self.assertNotEqual(user.name, 'new-name')
+
+        msg = Message.objects.get(id=1)
+        msg.reload()
+        self.assertEqual(msg.topic, topic)
+        self.assertEqual(msg.author, user)
+        self.assertEqual(msg.author.name, 'new-name')
+
+
     def test_list_lookup_not_checked_in_map(self):
         """Ensure we dereference list data correctly
         """