diff --git a/docs/guide/defining-documents.rst b/docs/guide/defining-documents.rst
index 2a8d5418..366d12c7 100644
--- a/docs/guide/defining-documents.rst
+++ b/docs/guide/defining-documents.rst
@@ -513,6 +513,9 @@ If a dictionary is passed then the following options are available:
     Allows you to automatically expire data from a collection by setting the
     time in seconds to expire the a field.
 
+:attr:`name` (Optional)
+    Allows you to specify a name for the index
+
 .. note::
 
     Inheritance adds extra fields indices see: :ref:`document-inheritance`.
diff --git a/docs/guide/document-instances.rst b/docs/guide/document-instances.rst
index 0e9fcef6..64f17c08 100644
--- a/docs/guide/document-instances.rst
+++ b/docs/guide/document-instances.rst
@@ -57,7 +57,8 @@ document values for example::
 
         def clean(self):
             """Ensures that only published essays have a `pub_date` and
-            automatically sets the pub_date if published and not set"""
+            automatically sets `pub_date` if essay is published and `pub_date`
+            is not set"""
             if self.status == 'Draft' and self.pub_date is not None:
                 msg = 'Draft entries should not have a publication date.'
                 raise ValidationError(msg)
diff --git a/mongoengine/connection.py b/mongoengine/connection.py
index 705dc25b..38ebb243 100644
--- a/mongoengine/connection.py
+++ b/mongoengine/connection.py
@@ -104,6 +104,18 @@ def register_connection(alias, db=None, name=None, host=None, port=None,
                 conn_settings['authentication_source'] = uri_options['authsource']
             if 'authmechanism' in uri_options:
                 conn_settings['authentication_mechanism'] = uri_options['authmechanism']
+            if IS_PYMONGO_3 and 'readpreference' in uri_options:
+                read_preferences = (
+                    ReadPreference.NEAREST,
+                    ReadPreference.PRIMARY,
+                    ReadPreference.PRIMARY_PREFERRED,
+                    ReadPreference.SECONDARY,
+                    ReadPreference.SECONDARY_PREFERRED)
+                read_pf_mode = uri_options['readpreference'].lower()
+                for preference in read_preferences:
+                    if preference.name.lower() == read_pf_mode:
+                        conn_settings['read_preference'] = preference
+                        break
         else:
             resolved_hosts.append(entity)
     conn_settings['host'] = resolved_hosts
diff --git a/mongoengine/context_managers.py b/mongoengine/context_managers.py
index ec2e9e8b..67c83581 100644
--- a/mongoengine/context_managers.py
+++ b/mongoengine/context_managers.py
@@ -145,18 +145,17 @@ class no_sub_classes(object):
         :param cls: the class to turn querying sub classes on
         """
         self.cls = cls
+        self.cls_initial_subclasses = None
 
     def __enter__(self):
         """Change the objects default and _auto_dereference values."""
-        self.cls._all_subclasses = self.cls._subclasses
-        self.cls._subclasses = (self.cls,)
+        self.cls_initial_subclasses = self.cls._subclasses
+        self.cls._subclasses = (self.cls._class_name,)
         return self.cls
 
     def __exit__(self, t, value, traceback):
         """Reset the default and _auto_dereference values."""
-        self.cls._subclasses = self.cls._all_subclasses
-        delattr(self.cls, '_all_subclasses')
-        return self.cls
+        self.cls._subclasses = self.cls_initial_subclasses
 
 
 class query_counter(object):
@@ -215,7 +214,7 @@ class query_counter(object):
         """Get the number of queries."""
         ignore_query = {'ns': {'$ne': '%s.system.indexes' % self.db.name}}
         count = self.db.system.profile.find(ignore_query).count() - self.counter
-        self.counter += 1
+        self.counter += 1       # Account for the query we just fired
         return count
 
 
diff --git a/mongoengine/fields.py b/mongoengine/fields.py
index 3c255798..6994b315 100644
--- a/mongoengine/fields.py
+++ b/mongoengine/fields.py
@@ -364,7 +364,8 @@ class FloatField(BaseField):
 
 
 class DecimalField(BaseField):
-    """Fixed-point decimal number field.
+    """Fixed-point decimal number field. Stores the value as a float by default unless `force_string` is used.
+    If using floats, beware of Decimal to float conversion (potential precision loss)
 
     .. versionchanged:: 0.8
     .. versionadded:: 0.3
@@ -375,7 +376,9 @@ class DecimalField(BaseField):
         """
         :param min_value: Validation rule for the minimum acceptable value.
         :param max_value: Validation rule for the maximum acceptable value.
-        :param force_string: Store as a string.
+        :param force_string: Store the value as a string (instead of a float).
+         Be aware that this affects query sorting and operation like lte, gte (as string comparison is applied)
+         and some query operator won't work (e.g: inc, dec)
         :param precision: Number of decimal places to store.
         :param rounding: The rounding rule from the python decimal library:
 
@@ -647,9 +650,17 @@ class EmbeddedDocumentField(BaseField):
     def document_type(self):
         if isinstance(self.document_type_obj, six.string_types):
             if self.document_type_obj == RECURSIVE_REFERENCE_CONSTANT:
-                self.document_type_obj = self.owner_document
+                resolved_document_type = self.owner_document
             else:
-                self.document_type_obj = get_document(self.document_type_obj)
+                resolved_document_type = get_document(self.document_type_obj)
+
+            if not issubclass(resolved_document_type, EmbeddedDocument):
+                # Due to the late resolution of the document_type
+                # There is a chance that it won't be an EmbeddedDocument (#1661)
+                self.error('Invalid embedded document class provided to an '
+                           'EmbeddedDocumentField')
+            self.document_type_obj = resolved_document_type
+
         return self.document_type_obj
 
     def to_python(self, value):
@@ -1029,11 +1040,13 @@ class ReferenceField(BaseField):
 
     .. code-block:: python
 
-        class Bar(Document):
-            content = StringField()
-            foo = ReferenceField('Foo')
+        class Org(Document):
+            owner = ReferenceField('User')
 
-        Foo.register_delete_rule(Bar, 'foo', NULLIFY)
+        class User(Document):
+            org = ReferenceField('Org', reverse_delete_rule=CASCADE)
+
+        User.register_delete_rule(Org, 'owner', DENY)
 
     .. versionchanged:: 0.5 added `reverse_delete_rule`
     """
diff --git a/mongoengine/queryset/transform.py b/mongoengine/queryset/transform.py
index 5f777f41..2effa249 100644
--- a/mongoengine/queryset/transform.py
+++ b/mongoengine/queryset/transform.py
@@ -147,7 +147,7 @@ def query(_doc_cls=None, **kwargs):
         if op is None or key not in mongo_query:
             mongo_query[key] = value
         elif key in mongo_query:
-            if isinstance(mongo_query[key], dict):
+            if isinstance(mongo_query[key], dict) and isinstance(value, dict):
                 mongo_query[key].update(value)
                 # $max/minDistance needs to come last - convert to SON
                 value_dict = mongo_query[key]
@@ -201,30 +201,37 @@ def update(_doc_cls=None, **update):
     format.
     """
     mongo_update = {}
+
     for key, value in update.items():
         if key == '__raw__':
             mongo_update.update(value)
             continue
+
         parts = key.split('__')
+
         # if there is no operator, default to 'set'
         if len(parts) < 3 and parts[0] not in UPDATE_OPERATORS:
             parts.insert(0, 'set')
+
         # Check for an operator and transform to mongo-style if there is
         op = None
         if parts[0] in UPDATE_OPERATORS:
             op = parts.pop(0)
             # Convert Pythonic names to Mongo equivalents
-            if op in ('push_all', 'pull_all'):
-                op = op.replace('_all', 'All')
-            elif op == 'dec':
+            operator_map = {
+                'push_all': 'pushAll',
+                'pull_all': 'pullAll',
+                'dec': 'inc',
+                'add_to_set': 'addToSet',
+                'set_on_insert': 'setOnInsert'
+            }
+            if op == 'dec':
                 # Support decrement by flipping a positive value's sign
                 # and using 'inc'
-                op = 'inc'
                 value = -value
-            elif op == 'add_to_set':
-                op = 'addToSet'
-            elif op == 'set_on_insert':
-                op = 'setOnInsert'
+            # If the operator doesn't found from operator map, the op value
+            # will stay unchanged
+            op = operator_map.get(op, op)
 
         match = None
         if parts[-1] in COMPARISON_OPERATORS:
@@ -291,6 +298,8 @@ def update(_doc_cls=None, **update):
                     value = field.prepare_query_value(op, value)
             elif op == 'unset':
                 value = 1
+            elif op == 'inc':
+                value = field.prepare_query_value(op, value)
 
         if match:
             match = '$' + match
diff --git a/tests/fields/fields.py b/tests/fields/fields.py
index 7352d242..362acec4 100644
--- a/tests/fields/fields.py
+++ b/tests/fields/fields.py
@@ -2147,6 +2147,15 @@ class FieldTest(MongoDBTestCase):
         ]))
         self.assertEqual(a.b.c.txt, 'hi')
 
+    def test_embedded_document_field_cant_reference_using_a_str_if_it_does_not_exist_yet(self):
+        raise SkipTest("Using a string reference in an EmbeddedDocumentField does not work if the class isnt registerd yet")
+
+        class MyDoc2(Document):
+            emb = EmbeddedDocumentField('MyDoc')
+
+        class MyDoc(EmbeddedDocument):
+            name = StringField()
+
     def test_embedded_document_validation(self):
         """Ensure that invalid embedded documents cannot be assigned to
         embedded document fields.
@@ -4388,6 +4397,44 @@ class EmbeddedDocumentListFieldTestCase(MongoDBTestCase):
         self.assertEqual(custom_data['a'], CustomData.c_field.custom_data['a'])
 
 
+class TestEmbeddedDocumentField(MongoDBTestCase):
+    def test___init___(self):
+        class MyDoc(EmbeddedDocument):
+            name = StringField()
+
+        field = EmbeddedDocumentField(MyDoc)
+        self.assertEqual(field.document_type_obj, MyDoc)
+
+        field2 = EmbeddedDocumentField('MyDoc')
+        self.assertEqual(field2.document_type_obj, 'MyDoc')
+
+    def test___init___throw_error_if_document_type_is_not_EmbeddedDocument(self):
+        with self.assertRaises(ValidationError):
+            EmbeddedDocumentField(dict)
+
+    def test_document_type_throw_error_if_not_EmbeddedDocument_subclass(self):
+
+        class MyDoc(Document):
+            name = StringField()
+
+        emb = EmbeddedDocumentField('MyDoc')
+        with self.assertRaises(ValidationError) as ctx:
+            emb.document_type
+        self.assertIn('Invalid embedded document class provided to an EmbeddedDocumentField', str(ctx.exception))
+
+    def test_embedded_document_field_only_allow_subclasses_of_embedded_document(self):
+        # Relates to #1661
+        class MyDoc(Document):
+            name = StringField()
+
+        with self.assertRaises(ValidationError):
+            class MyFailingDoc(Document):
+                emb = EmbeddedDocumentField(MyDoc)
+
+        with self.assertRaises(ValidationError):
+            class MyFailingdoc2(Document):
+                emb = EmbeddedDocumentField('MyDoc')
+
 class CachedReferenceFieldTest(MongoDBTestCase):
 
     def test_cached_reference_field_get_and_save(self):
diff --git a/tests/queryset/queryset.py b/tests/queryset/queryset.py
index a405e892..77308c26 100644
--- a/tests/queryset/queryset.py
+++ b/tests/queryset/queryset.py
@@ -3,6 +3,7 @@
 import datetime
 import unittest
 import uuid
+from decimal import Decimal
 
 from bson import DBRef, ObjectId
 from nose.plugins.skip import SkipTest
@@ -1202,6 +1203,14 @@ class QuerySetTest(unittest.TestCase):
         BlogPost.drop_collection()
         Blog.drop_collection()
 
+    def test_filter_chaining_with_regex(self):
+        person = self.Person(name='Guido van Rossum')
+        person.save()
+
+        people = self.Person.objects
+        people = people.filter(name__startswith='Gui').filter(name__not__endswith='tum')
+        self.assertEqual(people.count(), 1)
+
     def assertSequence(self, qs, expected):
         qs = list(qs)
         expected = list(expected)
@@ -1851,21 +1860,16 @@ class QuerySetTest(unittest.TestCase):
         self.assertEqual(
             1, BlogPost.objects(author__in=["%s" % me.pk]).count())
 
-    def test_update(self):
-        """Ensure that atomic updates work properly.
-        """
+    def test_update_intfield_operator(self):
         class BlogPost(Document):
-            name = StringField()
-            title = StringField()
             hits = IntField()
-            tags = ListField(StringField())
 
         BlogPost.drop_collection()
 
-        post = BlogPost(name="Test Post", hits=5, tags=['test'])
+        post = BlogPost(hits=5)
         post.save()
 
-        BlogPost.objects.update(set__hits=10)
+        BlogPost.objects.update_one(set__hits=10)
         post.reload()
         self.assertEqual(post.hits, 10)
 
@@ -1882,6 +1886,55 @@ class QuerySetTest(unittest.TestCase):
         post.reload()
         self.assertEqual(post.hits, 11)
 
+    def test_update_decimalfield_operator(self):
+        class BlogPost(Document):
+            review = DecimalField()
+
+        BlogPost.drop_collection()
+
+        post = BlogPost(review=3.5)
+        post.save()
+
+        BlogPost.objects.update_one(inc__review=0.1)             # test with floats
+        post.reload()
+        self.assertEqual(float(post.review), 3.6)
+
+        BlogPost.objects.update_one(dec__review=0.1)
+        post.reload()
+        self.assertEqual(float(post.review), 3.5)
+
+        BlogPost.objects.update_one(inc__review=Decimal(0.12))   # test with Decimal
+        post.reload()
+        self.assertEqual(float(post.review), 3.62)
+
+        BlogPost.objects.update_one(dec__review=Decimal(0.12))
+        post.reload()
+        self.assertEqual(float(post.review), 3.5)
+
+    def test_update_decimalfield_operator_not_working_with_force_string(self):
+        class BlogPost(Document):
+            review = DecimalField(force_string=True)
+
+        BlogPost.drop_collection()
+
+        post = BlogPost(review=3.5)
+        post.save()
+
+        with self.assertRaises(OperationError):
+            BlogPost.objects.update_one(inc__review=0.1)             # test with floats
+
+    def test_update_listfield_operator(self):
+        """Ensure that atomic updates work properly.
+        """
+        class BlogPost(Document):
+            tags = ListField(StringField())
+
+        BlogPost.drop_collection()
+
+        post = BlogPost(tags=['test'])
+        post.save()
+
+        # ListField operator
         BlogPost.objects.update(push__tags='mongo')
         post.reload()
         self.assertTrue('mongo' in post.tags)
@@ -1900,13 +1953,23 @@ class QuerySetTest(unittest.TestCase):
         post.reload()
         self.assertEqual(post.tags.count('unique'), 1)
 
-        self.assertNotEqual(post.hits, None)
-        BlogPost.objects.update_one(unset__hits=1)
-        post.reload()
-        self.assertEqual(post.hits, None)
+        BlogPost.drop_collection()
+
+    def test_update_unset(self):
+        class BlogPost(Document):
+            title = StringField()
 
         BlogPost.drop_collection()
 
+        post = BlogPost(title='garbage').save()
+
+        self.assertNotEqual(post.title, None)
+        BlogPost.objects.update_one(unset__title=1)
+        post.reload()
+        self.assertEqual(post.title, None)
+        pymongo_doc = BlogPost.objects.as_pymongo().first()
+        self.assertNotIn('title', pymongo_doc)
+
     @needs_mongodb_v26
     def test_update_push_with_position(self):
         """Ensure that the 'push' update with position works properly.
diff --git a/tests/test_connection.py b/tests/test_connection.py
index cdcf1377..f58b1a3e 100644
--- a/tests/test_connection.py
+++ b/tests/test_connection.py
@@ -364,6 +364,12 @@ class ConnectionTest(unittest.TestCase):
         date_doc = DateDoc.objects.first()
         self.assertEqual(d, date_doc.the_date)
 
+    def test_read_preference_from_parse(self):
+        if IS_PYMONGO_3:
+            from pymongo import ReadPreference
+            conn = connect(host="mongodb://a1.vpc,a2.vpc,a3.vpc/prod?readPreference=secondaryPreferred")
+            self.assertEqual(conn.read_preference, ReadPreference.SECONDARY_PREFERRED)
+
     def test_multiple_connection_settings(self):
         connect('mongoenginetest', alias='t1', host="localhost")
 
diff --git a/tests/test_context_managers.py b/tests/test_context_managers.py
index 0f6bf815..8c96016c 100644
--- a/tests/test_context_managers.py
+++ b/tests/test_context_managers.py
@@ -140,8 +140,6 @@ class ContextManagersTest(unittest.TestCase):
     def test_no_sub_classes(self):
         class A(Document):
             x = IntField()
-            y = IntField()
-
             meta = {'allow_inheritance': True}
 
         class B(A):
@@ -152,29 +150,29 @@ class ContextManagersTest(unittest.TestCase):
 
         A.drop_collection()
 
-        A(x=10, y=20).save()
-        A(x=15, y=30).save()
-        B(x=20, y=40).save()
-        B(x=30, y=50).save()
-        C(x=40, y=60).save()
+        A(x=10).save()
+        A(x=15).save()
+        B(x=20).save()
+        B(x=30).save()
+        C(x=40).save()
 
         self.assertEqual(A.objects.count(), 5)
         self.assertEqual(B.objects.count(), 3)
         self.assertEqual(C.objects.count(), 1)
 
-        with no_sub_classes(A) as A:
+        with no_sub_classes(A):
             self.assertEqual(A.objects.count(), 2)
 
             for obj in A.objects:
                 self.assertEqual(obj.__class__, A)
 
-        with no_sub_classes(B) as B:
+        with no_sub_classes(B):
             self.assertEqual(B.objects.count(), 2)
 
             for obj in B.objects:
                 self.assertEqual(obj.__class__, B)
 
-        with no_sub_classes(C) as C:
+        with no_sub_classes(C):
             self.assertEqual(C.objects.count(), 1)
 
             for obj in C.objects:
@@ -185,6 +183,32 @@ class ContextManagersTest(unittest.TestCase):
         self.assertEqual(B.objects.count(), 3)
         self.assertEqual(C.objects.count(), 1)
 
+    def test_no_sub_classes_modification_to_document_class_are_temporary(self):
+        class A(Document):
+            x = IntField()
+            meta = {'allow_inheritance': True}
+
+        class B(A):
+            z = IntField()
+
+        self.assertEqual(A._subclasses, ('A', 'A.B'))
+        with no_sub_classes(A):
+            self.assertEqual(A._subclasses, ('A',))
+        self.assertEqual(A._subclasses, ('A', 'A.B'))
+
+        self.assertEqual(B._subclasses, ('A.B',))
+        with no_sub_classes(B):
+            self.assertEqual(B._subclasses, ('A.B',))
+        self.assertEqual(B._subclasses, ('A.B',))
+
+    def test_no_subclass_context_manager_does_not_swallow_exception(self):
+        class User(Document):
+            name = StringField()
+
+        with self.assertRaises(TypeError):
+            with no_sub_classes(User):
+                raise TypeError()
+
     def test_query_counter(self):
         connect('mongoenginetest')
         db = get_db()
diff --git a/tests/utils.py b/tests/utils.py
index 4566d864..acd318c5 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -7,12 +7,12 @@ from mongoengine.connection import get_db, get_connection
 from mongoengine.python_support import IS_PYMONGO_3
 
 
-MONGO_TEST_DB = 'mongoenginetest'
+MONGO_TEST_DB = 'mongoenginetest'   # standard name for the test database
 
 
 class MongoDBTestCase(unittest.TestCase):
     """Base class for tests that need a mongodb connection
-    db is being dropped automatically
+    It ensures that the db is clean at the beginning and dropped at the end automatically
     """
 
     @classmethod
@@ -32,6 +32,7 @@ def get_mongodb_version():
     """
     return tuple(get_connection().server_info()['versionArray'])
 
+
 def _decorated_with_ver_requirement(func, ver_tuple):
     """Return a given function decorated with the version requirement
     for a particular MongoDB version tuple.
@@ -50,18 +51,21 @@ def _decorated_with_ver_requirement(func, ver_tuple):
 
     return _inner
 
+
 def needs_mongodb_v26(func):
     """Raise a SkipTest exception if we're working with MongoDB version
     lower than v2.6.
     """
     return _decorated_with_ver_requirement(func, (2, 6))
 
+
 def needs_mongodb_v3(func):
     """Raise a SkipTest exception if we're working with MongoDB version
     lower than v3.0.
     """
     return _decorated_with_ver_requirement(func, (3, 0))
 
+
 def skip_pymongo3(f):
     """Raise a SkipTest exception if we're running a test against
     PyMongo v3.x.