Merge pull request #709 from wpjunior/cached-reference-field

CachedReferenceField implementation

docs/apireference.rst

@@ -84,6 +84,7 @@ Fields
 .. autoclass:: mongoengine.fields.MapField
 .. autoclass:: mongoengine.fields.ReferenceField
 .. autoclass:: mongoengine.fields.GenericReferenceField
+.. autoclass:: mongoengine.fields.CachedReferenceField
 .. autoclass:: mongoengine.fields.BinaryField
 .. autoclass:: mongoengine.fields.FileField
 .. autoclass:: mongoengine.fields.ImageField

mongoengine/base/document.py

@@ -23,6 +23,7 @@ __all__ = ('BaseDocument', 'NON_FIELD_ERRORS')
 
 NON_FIELD_ERRORS = '__all__'
 
+
 class BaseDocument(object):
     __slots__ = ('_changed_fields', '_initialised', '_created', '_data',
                  '_dynamic_fields', '_auto_id_field', '_db_field_map', '_cls', '__weakref__')
@@ -50,7 +51,8 @@ class BaseDocument(object):
             for value in args:
                 name = next(field)
                 if name in values:
-                    raise TypeError("Multiple values for keyword argument '" + name + "'")
+                    raise TypeError(
+                        "Multiple values for keyword argument '" + name + "'")
                 values[name] = value
         __auto_convert = values.pop("__auto_convert", True)
         signals.pre_init.send(self.__class__, document=self, values=values)
@@ -58,7 +60,8 @@ class BaseDocument(object):
         if self.STRICT and not self._dynamic:
             self._data = StrictDict.create(allowed_keys=self._fields_ordered)()
         else:
-            self._data = SemiStrictDict.create(allowed_keys=self._fields_ordered)()
+            self._data = SemiStrictDict.create(
+                allowed_keys=self._fields_ordered)()
 
         _created = values.pop("_created", True)
         self._data = {}
@@ -257,23 +260,41 @@ class BaseDocument(object):
         """
         pass
 
-    def to_mongo(self, use_db_field=True):
+    def to_mongo(self, use_db_field=True, fields=[]):
-        """Return as SON data ready for use with MongoDB.
+        """
+        Return as SON data ready for use with MongoDB.
         """
         data = SON()
         data["_id"] = None
         data['_cls'] = self._class_name
+        EmbeddedDocumentField = _import_class("EmbeddedDocumentField")
+        # only root fields ['test1.a', 'test2'] => ['test1', 'test2']
+        root_fields = set([f.split('.')[0] for f in fields])
 
         for field_name in self:
+            if root_fields and field_name not in root_fields:
+                continue
+
             value = self._data.get(field_name, None)
             field = self._fields.get(field_name)
+
             if field is None and self._dynamic:
                 field = self._dynamic_fields.get(field_name)
 
             if value is not None:
-                EmbeddedDocument = _import_class("EmbeddedDocument")
+
-                if isinstance(value, (EmbeddedDocument)) and use_db_field==False:
+                if isinstance(field, (EmbeddedDocumentField)):
-                    value = field.to_mongo(value, use_db_field)
+                    if fields:
+                        key = '%s.' % field_name
+                        embedded_fields = [
+                            i.replace(key, '') for i in fields
+                            if i.startswith(key)]
+
+                    else:
+                        embedded_fields = []
+
+                    value = field.to_mongo(value, use_db_field=use_db_field,
+                                           fields=embedded_fields)
                 else:
                     value = field.to_mongo(value)
 
@@ -321,7 +342,8 @@ class BaseDocument(object):
                    self._data.get(name)) for name in self._fields_ordered]
 
         EmbeddedDocumentField = _import_class("EmbeddedDocumentField")
-        GenericEmbeddedDocumentField = _import_class("GenericEmbeddedDocumentField")
+        GenericEmbeddedDocumentField = _import_class(
+            "GenericEmbeddedDocumentField")
 
         for field, value in fields:
             if value is not None:
@@ -352,7 +374,8 @@ class BaseDocument(object):
         """Converts a document to JSON.
         :param use_db_field: Set to True by default but enables the output of the json structure with the field names and not the mongodb store db_names in case of set to False
         """
-        use_db_field = kwargs.pop('use_db_field') if kwargs.has_key('use_db_field') else True
+        use_db_field = kwargs.pop('use_db_field') if kwargs.has_key(
+            'use_db_field') else True
         return json_util.dumps(self.to_mongo(use_db_field),  *args, **kwargs)
 
     @classmethod
@@ -454,7 +477,8 @@ class BaseDocument(object):
                 changed_fields += ["%s%s" % (list_key, k)
                                    for k in changed if k]
             elif isinstance(value, (list, tuple, dict)):
-                self._nestable_types_changed_fields(changed_fields, list_key, value, inspected)
+                self._nestable_types_changed_fields(
+                    changed_fields, list_key, value, inspected)
 
     def _get_changed_fields(self, inspected=None):
         """Returns a list of all fields that have explicitly been changed.
@@ -493,7 +517,8 @@ class BaseDocument(object):
                 if (hasattr(field, 'field') and
                         isinstance(field.field, ReferenceField)):
                     continue
-                self._nestable_types_changed_fields(changed_fields, key, data, inspected)
+                self._nestable_types_changed_fields(
+                    changed_fields, key, data, inspected)
         return changed_fields
 
     def _delta(self):
@@ -631,7 +656,8 @@ class BaseDocument(object):
             raise InvalidDocumentError(msg)
 
         if cls.STRICT:
-            data = dict((k, v) for k,v in data.iteritems() if k in cls._fields)
+            data = dict((k, v)
+                        for k, v in data.iteritems() if k in cls._fields)
         obj = cls(__auto_convert=False, _created=False, **data)
         obj._changed_fields = changed_fields
         if not _auto_dereference:
@@ -794,7 +820,8 @@ class BaseDocument(object):
         geo_field_type_names = ["EmbeddedDocumentField", "GeoPointField",
                                 "PointField", "LineStringField", "PolygonField"]
 
-        geo_field_types = tuple([_import_class(field) for field in geo_field_type_names])
+        geo_field_types = tuple([_import_class(field)
+                                 for field in geo_field_type_names])
 
         for field in cls._fields.values():
             if not isinstance(field, geo_field_types):
@@ -804,7 +831,8 @@ class BaseDocument(object):
                 if field_cls in inspected:
                     continue
                 if hasattr(field_cls, '_geo_indices'):
-                    geo_indices += field_cls._geo_indices(inspected, parent_field=field.db_field)
+                    geo_indices += field_cls._geo_indices(
+                        inspected, parent_field=field.db_field)
             elif field._geo_index:
                 field_name = field.db_field
                 if parent_field:

mongoengine/base/fields.py

@@ -11,10 +11,12 @@ from mongoengine.errors import ValidationError
 from mongoengine.base.common import ALLOW_INHERITANCE
 from mongoengine.base.datastructures import BaseDict, BaseList
 
-__all__ = ("BaseField", "ComplexBaseField", "ObjectIdField", "GeoJsonBaseField")
+__all__ = ("BaseField", "ComplexBaseField",
+           "ObjectIdField", "GeoJsonBaseField")
 
 
 class BaseField(object):
+
     """A base class for fields in a MongoDB document. Instances of this class
     may be added to subclasses of `Document` to define a document's schema.
 
@@ -60,6 +62,7 @@ class BaseField(object):
             used when generating model forms from the document model.
         """
         self.db_field = (db_field or name) if not primary_key else '_id'
+
         if name:
             msg = "Fields' 'name' attribute deprecated in favour of 'db_field'"
             warnings.warn(msg, DeprecationWarning)
@@ -175,6 +178,7 @@ class BaseField(object):
 
 
 class ComplexBaseField(BaseField):
+
     """Handles complex fields, such as lists / dictionaries.
 
     Allows for nesting of embedded documents inside complex types.
@@ -384,6 +388,7 @@ class ComplexBaseField(BaseField):
 
 
 class ObjectIdField(BaseField):
+
     """A field wrapper around MongoDB's ObjectIds.
     """
 
@@ -412,6 +417,7 @@ class ObjectIdField(BaseField):
 
 
 class GeoJsonBaseField(BaseField):
+
     """A geo json field storing a geojson style object.
     .. versionadded:: 0.8
     """
@@ -435,7 +441,8 @@ class GeoJsonBaseField(BaseField):
         if isinstance(value, dict):
             if set(value.keys()) == set(['type', 'coordinates']):
                 if value['type'] != self._type:
-                    self.error('%s type must be "%s"' % (self._name, self._type))
+                    self.error('%s type must be "%s"' %
+                               (self._name, self._type))
                 return self.validate(value['coordinates'])
             else:
                 self.error('%s can only accept a valid GeoJson dictionary'

mongoengine/base/metaclasses.py

@@ -16,6 +16,7 @@ __all__ = ('DocumentMetaclass', 'TopLevelDocumentMetaclass')
 
 
 class DocumentMetaclass(type):
+
     """Metaclass for all documents.
     """
 
@@ -29,6 +30,7 @@ class DocumentMetaclass(type):
             return super_new(cls, name, bases, attrs)
 
         attrs['_is_document'] = attrs.get('_is_document', False)
+        attrs['_cached_reference_fields'] = []
 
         # EmbeddedDocuments could have meta data for inheritance
         if 'meta' in attrs:
@@ -141,7 +143,8 @@ class DocumentMetaclass(type):
                 base._subclasses += (_cls,)
             base._types = base._subclasses   # TODO depreciate _types
 
-        Document, EmbeddedDocument, DictField = cls._import_classes()
+        (Document, EmbeddedDocument, DictField,
+         CachedReferenceField) = cls._import_classes()
 
         if issubclass(new_class, Document):
             new_class._collection = None
@@ -170,6 +173,20 @@ class DocumentMetaclass(type):
             f = field
             f.owner_document = new_class
             delete_rule = getattr(f, 'reverse_delete_rule', DO_NOTHING)
+            if isinstance(f, CachedReferenceField):
+
+                if issubclass(new_class, EmbeddedDocument):
+                    raise InvalidDocumentError(
+                        "CachedReferenceFields is not allowed in EmbeddedDocuments")
+                if not f.document_type:
+                    raise InvalidDocumentError(
+                        "Document is not avaiable to sync")
+
+                if f.auto_sync:
+                    f.start_listener()
+
+                f.document_type._cached_reference_fields.append(f)
+
             if isinstance(f, ComplexBaseField) and hasattr(f, 'field'):
                 delete_rule = getattr(f.field,
                                       'reverse_delete_rule',
@@ -224,10 +241,12 @@ class DocumentMetaclass(type):
         Document = _import_class('Document')
         EmbeddedDocument = _import_class('EmbeddedDocument')
         DictField = _import_class('DictField')
-        return (Document, EmbeddedDocument, DictField)
+        CachedReferenceField = _import_class('CachedReferenceField')
+        return (Document, EmbeddedDocument, DictField, CachedReferenceField)
 
 
 class TopLevelDocumentMetaclass(DocumentMetaclass):
+
     """Metaclass for top-level documents (i.e. documents that have their own
     collection in the database.
     """
@@ -387,6 +406,7 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
 
 
 class MetaDict(dict):
+
     """Custom dictionary for meta classes.
     Handles the merging of set indexes
     """
@@ -401,5 +421,6 @@ class MetaDict(dict):
 
 
 class BasesTuple(tuple):
+
     """Special class to handle introspection of bases tuple in __new__"""
     pass

mongoengine/common.py

@@ -25,6 +25,7 @@ def _import_class(cls_name):
                      'GenericEmbeddedDocumentField', 'GeoPointField',
                      'PointField', 'LineStringField', 'ListField',
                      'PolygonField', 'ReferenceField', 'StringField',
+                     'CachedReferenceField',
                      'ComplexBaseField', 'GeoJsonBaseField')
     queryset_classes = ('OperationError',)
     deref_classes = ('DeReference',)

mongoengine/fields.py

@@ -34,13 +34,14 @@ except ImportError:
     Image = None
     ImageOps = None
 
-__all__ = ['StringField',  'URLField',  'EmailField',  'IntField',  'LongField',
+__all__ = [
+    'StringField', 'URLField', 'EmailField', 'IntField', 'LongField',
     'FloatField', 'DecimalField', 'BooleanField', 'DateTimeField',
     'ComplexDateTimeField', 'EmbeddedDocumentField', 'ObjectIdField',
     'GenericEmbeddedDocumentField', 'DynamicField', 'ListField',
     'SortedListField', 'DictField', 'MapField', 'ReferenceField',
-           'GenericReferenceField',  'BinaryField',  'GridFSError',
+    'CachedReferenceField', 'GenericReferenceField', 'BinaryField',
-           'GridFSProxy',  'FileField',  'ImageGridFsProxy',
+    'GridFSError', 'GridFSProxy', 'FileField', 'ImageGridFsProxy',
     'ImproperlyConfigured', 'ImageField', 'GeoPointField', 'PointField',
     'LineStringField', 'PolygonField', 'SequenceField', 'UUIDField',
     'GeoJsonBaseField']
@@ -50,6 +51,7 @@ RECURSIVE_REFERENCE_CONSTANT = 'self'
 
 
 class StringField(BaseField):
+
     """A unicode string field.
     """
 
@@ -109,6 +111,7 @@ class StringField(BaseField):
 
 
 class URLField(StringField):
+
     """A field that validates input as an URL.
 
     .. versionadded:: 0.3
@@ -116,7 +119,8 @@ class URLField(StringField):
 
     _URL_REGEX = re.compile(
         r'^(?:http|ftp)s?://'  # http:// or https://
-        r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}\.?)|'  # domain...
+        # domain...
+        r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}\.?)|'
         r'localhost|'  # localhost...
         r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})'  # ...or ip
         r'(?::\d+)?'  # optional port
@@ -145,15 +149,19 @@ class URLField(StringField):
 
 
 class EmailField(StringField):
+
     """A field that validates input as an E-Mail-Address.
 
     .. versionadded:: 0.4
     """
 
     EMAIL_REGEX = re.compile(
-        r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*"  # dot-atom
+        # dot-atom
-        r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*"'  # quoted-string
+        r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*"
-        r')@(?:[A-Z0-9](?:[A-Z0-9-]{0,253}[A-Z0-9])?\.)+[A-Z]{2,6}$', re.IGNORECASE  # domain
+        # quoted-string
+        r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*"'
+        # domain
+        r')@(?:[A-Z0-9](?:[A-Z0-9-]{0,253}[A-Z0-9])?\.)+[A-Z]{2,6}$', re.IGNORECASE
     )
 
     def validate(self, value):
@@ -163,6 +171,7 @@ class EmailField(StringField):
 
 
 class IntField(BaseField):
+
     """An 32-bit integer field.
     """
 
@@ -197,6 +206,7 @@ class IntField(BaseField):
 
 
 class LongField(BaseField):
+
     """An 64-bit integer field.
     """
 
@@ -231,6 +241,7 @@ class LongField(BaseField):
 
 
 class FloatField(BaseField):
+
     """An floating point number field.
     """
 
@@ -265,6 +276,7 @@ class FloatField(BaseField):
 
 
 class DecimalField(BaseField):
+
     """A fixed-point decimal number field.
 
     .. versionchanged:: 0.8
@@ -338,6 +350,7 @@ class DecimalField(BaseField):
 
 
 class BooleanField(BaseField):
+
     """A boolean field type.
 
     .. versionadded:: 0.1.2
@@ -356,6 +369,7 @@ class BooleanField(BaseField):
 
 
 class DateTimeField(BaseField):
+
     """A datetime field.
 
     Uses the python-dateutil library if available alternatively use time.strptime
@@ -423,6 +437,7 @@ class DateTimeField(BaseField):
 
 
 class ComplexDateTimeField(StringField):
+
     """
     ComplexDateTimeField handles microseconds exactly instead of rounding
     like DateTimeField does.
@@ -525,6 +540,7 @@ class ComplexDateTimeField(StringField):
 
 
 class EmbeddedDocumentField(BaseField):
+
     """An embedded document field - with a declared document_type.
     Only valid values are subclasses of :class:`~mongoengine.EmbeddedDocument`.
     """
@@ -551,10 +567,11 @@ class EmbeddedDocumentField(BaseField):
             return self.document_type._from_son(value)
         return value
 
-    def to_mongo(self, value, use_db_field=True):
+    def to_mongo(self, value, use_db_field=True, fields=[]):
         if not isinstance(value, self.document_type):
             return value
-        return self.document_type.to_mongo(value, use_db_field)
+        return self.document_type.to_mongo(value, use_db_field,
+                                           fields=fields)
 
     def validate(self, value, clean=True):
         """Make sure that the document instance is an instance of the
@@ -574,6 +591,7 @@ class EmbeddedDocumentField(BaseField):
 
 
 class GenericEmbeddedDocumentField(BaseField):
+
     """A generic embedded document field - allows any
     :class:`~mongoengine.EmbeddedDocument` to be stored.
 
@@ -612,6 +630,7 @@ class GenericEmbeddedDocumentField(BaseField):
 
 
 class DynamicField(BaseField):
+
     """A truly dynamic field type capable of handling different and varying
     types of data.
 
@@ -675,6 +694,7 @@ class DynamicField(BaseField):
 
 
 class ListField(ComplexBaseField):
+
     """A list field that wraps a standard field, allowing multiple instances
     of the field to be used as a list in the database.
 
@@ -708,6 +728,7 @@ class ListField(ComplexBaseField):
 
 
 class SortedListField(ListField):
+
     """A ListField that sorts the contents of its list before writing to
     the database in order to ensure that a sorted list is always
     retrieved.
@@ -739,6 +760,7 @@ class SortedListField(ListField):
                           reverse=self._order_reverse)
         return sorted(value, reverse=self._order_reverse)
 
+
 def key_not_string(d):
     """ Helper function to recursively determine if any key in a dictionary is
     not a string.
@@ -747,6 +769,7 @@ def key_not_string(d):
         if not isinstance(k, basestring) or (isinstance(v, dict) and key_not_string(v)):
             return True
 
+
 def key_has_dot_or_dollar(d):
     """ Helper function to recursively determine if any key in a dictionary
     contains a dot or a dollar sign.
@@ -755,7 +778,9 @@ def key_has_dot_or_dollar(d):
         if ('.' in k or '$' in k) or (isinstance(v, dict) and key_has_dot_or_dollar(v)):
             return True
 
+
 class DictField(ComplexBaseField):
+
     """A dictionary field that wraps a standard Python dictionary. This is
     similar to an embedded document, but the structure is not defined.
 
@@ -807,6 +832,7 @@ class DictField(ComplexBaseField):
 
 
 class MapField(DictField):
+
     """A field that maps a name to a specified field type. Similar to
     a DictField, except the 'value' of each item must match the specified
     field type.
@@ -822,6 +848,7 @@ class MapField(DictField):
 
 
 class ReferenceField(BaseField):
+
     """A reference to a document that will be automatically dereferenced on
     access (lazily).
 
@@ -955,7 +982,147 @@ class ReferenceField(BaseField):
         return self.document_type._fields.get(member_name)
 
 
+class CachedReferenceField(BaseField):
+
+    """
+    A referencefield with cache fields to porpuse pseudo-joins
+    .. versionadded:: 0.9
+    """
+
+    def __init__(self, document_type, fields=[], auto_sync=True, **kwargs):
+        """Initialises the Cached Reference Field.
+
+        :param fields:  A list of fields to be cached in document
+        :param auto_sync: if True documents are auto updated.
+        """
+        if not isinstance(document_type, basestring) and \
+                not issubclass(document_type, (Document, basestring)):
+
+            self.error('Argument to CachedReferenceField constructor must be a'
+                       ' document class or a string')
+
+        self.auto_sync = auto_sync
+        self.document_type_obj = document_type
+        self.fields = fields
+        super(CachedReferenceField, self).__init__(**kwargs)
+
+    def start_listener(self):
+        from mongoengine import signals
+        signals.post_save.connect(self.on_document_pre_save,
+                                  sender=self.document_type)
+
+    def on_document_pre_save(self, sender, document, created, **kwargs):
+        if not created:
+            update_kwargs = dict(
+                ('set__%s__%s' % (self.name, k), v)
+                for k, v in document._delta()[0].items()
+                if k in self.fields)
+
+            if update_kwargs:
+                filter_kwargs = {}
+                filter_kwargs[self.name] = document
+
+                self.owner_document.objects(
+                    **filter_kwargs).update(**update_kwargs)
+
+    def to_python(self, value):
+        if isinstance(value, dict):
+            collection = self.document_type._get_collection_name()
+            value = DBRef(
+                collection, self.document_type.id.to_python(value['_id']))
+
+        return value
+
+    @property
+    def document_type(self):
+        if isinstance(self.document_type_obj, basestring):
+            if self.document_type_obj == RECURSIVE_REFERENCE_CONSTANT:
+                self.document_type_obj = self.owner_document
+            else:
+                self.document_type_obj = get_document(self.document_type_obj)
+        return self.document_type_obj
+
+    def __get__(self, instance, owner):
+        if instance is None:
+            # Document class being used rather than a document object
+            return self
+
+        # Get value from document instance if available
+        value = instance._data.get(self.name)
+        self._auto_dereference = instance._fields[self.name]._auto_dereference
+        # Dereference DBRefs
+        if self._auto_dereference and isinstance(value, DBRef):
+            value = self.document_type._get_db().dereference(value)
+            if value is not None:
+                instance._data[self.name] = self.document_type._from_son(value)
+
+        return super(CachedReferenceField, self).__get__(instance, owner)
+
+    def to_mongo(self, document):
+        id_field_name = self.document_type._meta['id_field']
+        id_field = self.document_type._fields[id_field_name]
+        doc_tipe = self.document_type
+
+        if isinstance(document, Document):
+            # We need the id from the saved object to create the DBRef
+            id_ = document.pk
+            if id_ is None:
+                self.error('You can only reference documents once they have'
+                           ' been saved to the database')
+        else:
+            self.error('Only accept a document object')
+
+        value = SON((
+            ("_id", id_field.to_mongo(id_)),
+        ))
+
+        value.update(dict(document.to_mongo(fields=self.fields)))
+        return value
+
+    def prepare_query_value(self, op, value):
+        if value is None:
+            return None
+
+        if isinstance(value, Document):
+            if value.pk is None:
+                self.error('You can only reference documents once they have'
+                           ' been saved to the database')
+            return {'_id': value.pk}
+
+        raise NotImplementedError
+
+    def validate(self, value):
+
+        if not isinstance(value, (self.document_type)):
+            self.error("A CachedReferenceField only accepts documents")
+
+        if isinstance(value, Document) and value.id is None:
+            self.error('You can only reference documents once they have been '
+                       'saved to the database')
+
+    def lookup_member(self, member_name):
+        return self.document_type._fields.get(member_name)
+
+    def sync_all(self):
+        """
+        Sync all cached fields on demand.
+        Caution: this operation may be slower.
+        """
+        update_key = 'set__%s' % self.name
+
+        for doc in self.document_type.objects:
+            filter_kwargs = {}
+            filter_kwargs[self.name] = doc
+
+            update_kwargs = {}
+            update_kwargs[update_key] = doc
+
+            self.owner_document.objects(
+                **filter_kwargs).update(**update_kwargs)
+
+
 class GenericReferenceField(BaseField):
+
     """A reference to *any* :class:`~mongoengine.document.Document` subclass
     that will be automatically dereferenced on access (lazily).
 
@@ -974,6 +1141,7 @@ class GenericReferenceField(BaseField):
             return self
 
         value = instance._data.get(self.name)
+
         self._auto_dereference = instance._fields[self.name]._auto_dereference
         if self._auto_dereference and isinstance(value, (dict, SON)):
             instance._data[self.name] = self.dereference(value)
@@ -1036,6 +1204,7 @@ class GenericReferenceField(BaseField):
 
 
 class BinaryField(BaseField):
+
     """A binary data field.
     """
 
@@ -1067,6 +1236,7 @@ class GridFSError(Exception):
 
 
 class GridFSProxy(object):
+
     """Proxy object to handle writing and reading of files to and from GridFS
 
     .. versionadded:: 0.4
@@ -1121,7 +1291,8 @@ class GridFSProxy(object):
         return '<%s: %s>' % (self.__class__.__name__, self.grid_id)
 
     def __str__(self):
-        name = getattr(self.get(), 'filename', self.grid_id) if self.get() else '(no file)'
+        name = getattr(
+            self.get(), 'filename', self.grid_id) if self.get() else '(no file)'
         return '<%s: %s>' % (self.__class__.__name__, name)
 
     def __eq__(self, other):
@@ -1135,7 +1306,8 @@ class GridFSProxy(object):
     @property
     def fs(self):
         if not self._fs:
-            self._fs = gridfs.GridFS(get_db(self.db_alias), self.collection_name)
+            self._fs = gridfs.GridFS(
+                get_db(self.db_alias), self.collection_name)
         return self._fs
 
     def get(self, id=None):
@@ -1209,6 +1381,7 @@ class GridFSProxy(object):
 
 
 class FileField(BaseField):
+
     """A GridFS storage field.
 
     .. versionadded:: 0.4
@@ -1253,7 +1426,8 @@ class FileField(BaseField):
                     pass
 
             # Create a new proxy object as we don't already have one
-            instance._data[key] = self.get_proxy_obj(key=key, instance=instance)
+            instance._data[key] = self.get_proxy_obj(
+                key=key, instance=instance)
             instance._data[key].put(value)
         else:
             instance._data[key] = value
@@ -1291,11 +1465,13 @@ class FileField(BaseField):
 
 
 class ImageGridFsProxy(GridFSProxy):
+
     """
     Proxy for ImageField
 
     versionadded: 0.6
     """
+
     def put(self, file_obj, **kwargs):
         """
         Insert a image in database
@@ -1341,7 +1517,8 @@ class ImageGridFsProxy(GridFSProxy):
             size = field.thumbnail_size
 
             if size['force']:
-                thumbnail = ImageOps.fit(img, (size['width'], size['height']), Image.ANTIALIAS)
+                thumbnail = ImageOps.fit(
+                    img, (size['width'], size['height']), Image.ANTIALIAS)
             else:
                 thumbnail = img.copy()
                 thumbnail.thumbnail((size['width'],
@@ -1367,7 +1544,7 @@ class ImageGridFsProxy(GridFSProxy):
                                                  **kwargs)
 
     def delete(self, *args, **kwargs):
-        #deletes thumbnail
+        # deletes thumbnail
         out = self.get()
         if out and out.thumbnail_id:
             self.fs.delete(out.thumbnail_id)
@@ -1427,6 +1604,7 @@ class ImproperlyConfigured(Exception):
 
 
 class ImageField(FileField):
+
     """
     A Image File storage field.
 
@@ -1465,6 +1643,7 @@ class ImageField(FileField):
 
 
 class SequenceField(BaseField):
+
     """Provides a sequental counter see:
      http://www.mongodb.org/display/DOCS/Object+IDs#ObjectIDs-SequenceNumbers
 
@@ -1534,7 +1713,7 @@ class SequenceField(BaseField):
         data = collection.find_one({"_id": sequence_id})
 
         if data:
-            return self.value_decorator(data['next']+1)
+            return self.value_decorator(data['next'] + 1)
 
         return self.value_decorator(1)
 
@@ -1579,6 +1758,7 @@ class SequenceField(BaseField):
 
 
 class UUIDField(BaseField):
+
     """A UUID field.
 
     .. versionadded:: 0.6
@@ -1631,6 +1811,7 @@ class UUIDField(BaseField):
 
 
 class GeoPointField(BaseField):
+
     """A list storing a longitude and latitude coordinate.
 
     .. note:: this represents a generic point in a 2D plane and a legacy way of
@@ -1651,13 +1832,16 @@ class GeoPointField(BaseField):
                        'of (x, y)')
 
         if not len(value) == 2:
-            self.error("Value (%s) must be a two-dimensional point" % repr(value))
+            self.error("Value (%s) must be a two-dimensional point" %
+                       repr(value))
         elif (not isinstance(value[0], (float, int)) or
               not isinstance(value[1], (float, int))):
-            self.error("Both values (%s) in point must be float or int" % repr(value))
+            self.error(
+                "Both values (%s) in point must be float or int" % repr(value))
 
 
 class PointField(GeoJsonBaseField):
+
     """A GeoJSON field storing a longitude and latitude coordinate.
 
     The data is represented as:
@@ -1677,6 +1861,7 @@ class PointField(GeoJsonBaseField):
 
 
 class LineStringField(GeoJsonBaseField):
+
     """A GeoJSON field storing a line of longitude and latitude coordinates.
 
     The data is represented as:
@@ -1695,6 +1880,7 @@ class LineStringField(GeoJsonBaseField):
 
 
 class PolygonField(GeoJsonBaseField):
+
     """A GeoJSON field storing a polygon of longitude and latitude coordinates.
 
     The data is represented as:

mongoengine/queryset/transform.py

@@ -60,14 +60,20 @@ def query(_doc_cls=None, _field_operation=False, **query):
                 raise InvalidQueryError(e)
             parts = []
 
+            CachedReferenceField = _import_class('CachedReferenceField')
+
             cleaned_fields = []
             for field in fields:
                 append_field = True
                 if isinstance(field, basestring):
                     parts.append(field)
                     append_field = False
+                # is last and CachedReferenceField
+                elif isinstance(field, CachedReferenceField) and fields[-1] == field:
+                    parts.append('%s._id' % field.db_field)
                 else:
                     parts.append(field.db_field)
+
                 if append_field:
                     cleaned_fields.append(field)
 
@@ -86,6 +92,10 @@ def query(_doc_cls=None, _field_operation=False, **query):
                         value = field
                 else:
                     value = field.prepare_query_value(op, value)
+
+                    if isinstance(field, CachedReferenceField) and value:
+                        value = value['_id']
+
             elif op in ('in', 'nin', 'all', 'near') and not isinstance(value, dict):
                 # 'in', 'nin' and 'all' require a list of values
                 value = [field.prepare_query_value(op, v) for v in value]
@@ -125,10 +135,12 @@ def query(_doc_cls=None, _field_operation=False, **query):
                                 continue
                             value_son[k] = v
                         if (get_connection().max_wire_version <= 1):
-                            value_son['$maxDistance'] = value_dict['$maxDistance']
+                            value_son['$maxDistance'] = value_dict[
+                                '$maxDistance']
                         else:
                             value_son['$near'] = SON(value_son['$near'])
-                            value_son['$near']['$maxDistance'] = value_dict['$maxDistance']
+                            value_son['$near'][
+                                '$maxDistance'] = value_dict['$maxDistance']
                     else:
                         for k, v in value_dict.iteritems():
                             if k == '$maxDistance':
@@ -264,7 +276,8 @@ def update(_doc_cls=None, **update):
             if ListField in field_classes:
                 # Join all fields via dot notation to the last ListField
                 # Then process as normal
-                last_listField = len(cleaned_fields) - field_classes.index(ListField)
+                last_listField = len(
+                    cleaned_fields) - field_classes.index(ListField)
                 key = ".".join(parts[:last_listField])
                 parts = parts[last_listField:]
                 parts.insert(0, key)

tests/fields/fields.py

@@ -47,7 +47,8 @@ class FieldTest(unittest.TestCase):
 
         # Confirm saving now would store values
         data_to_be_saved = sorted(person.to_mongo().keys())
-        self.assertEqual(data_to_be_saved, ['age', 'created', 'name', 'userid'])
+        self.assertEqual(
+            data_to_be_saved, ['age', 'created', 'name', 'userid'])
 
         self.assertTrue(person.validate() is None)
 
@@ -63,7 +64,8 @@ class FieldTest(unittest.TestCase):
 
         # Confirm introspection changes nothing
         data_to_be_saved = sorted(person.to_mongo().keys())
-        self.assertEqual(data_to_be_saved, ['age', 'created', 'name', 'userid'])
+        self.assertEqual(
+            data_to_be_saved, ['age', 'created', 'name', 'userid'])
 
     def test_default_values_set_to_None(self):
         """Ensure that default field values are used when creating a document.
@@ -587,7 +589,8 @@ class FieldTest(unittest.TestCase):
 
         LogEntry.drop_collection()
 
-        # Post UTC - microseconds are rounded (down) nearest millisecond and dropped
+        # Post UTC - microseconds are rounded (down) nearest millisecond and
+        # dropped
         d1 = datetime.datetime(1970, 01, 01, 00, 00, 01, 999)
         d2 = datetime.datetime(1970, 01, 01, 00, 00, 01)
         log = LogEntry()
@@ -688,7 +691,8 @@ class FieldTest(unittest.TestCase):
 
         LogEntry.drop_collection()
 
-        # Post UTC - microseconds are rounded (down) nearest millisecond and dropped - with default datetimefields
+        # Post UTC - microseconds are rounded (down) nearest millisecond and
+        # dropped - with default datetimefields
         d1 = datetime.datetime(1970, 01, 01, 00, 00, 01, 999)
         log = LogEntry()
         log.date = d1
@@ -696,14 +700,16 @@ class FieldTest(unittest.TestCase):
         log.reload()
         self.assertEqual(log.date, d1)
 
-        # Post UTC - microseconds are rounded (down) nearest millisecond - with default datetimefields
+        # Post UTC - microseconds are rounded (down) nearest millisecond - with
+        # default datetimefields
         d1 = datetime.datetime(1970, 01, 01, 00, 00, 01, 9999)
         log.date = d1
         log.save()
         log.reload()
         self.assertEqual(log.date, d1)
 
-        # Pre UTC dates microseconds below 1000 are dropped - with default datetimefields
+        # Pre UTC dates microseconds below 1000 are dropped - with default
+        # datetimefields
         d1 = datetime.datetime(1969, 12, 31, 23, 59, 59, 999)
         log.date = d1
         log.save()
@@ -929,12 +935,16 @@ class FieldTest(unittest.TestCase):
         post.save()
 
         self.assertEqual(BlogPost.objects.count(), 3)
-        self.assertEqual(BlogPost.objects.filter(info__exact='test').count(), 1)
+        self.assertEqual(
-        self.assertEqual(BlogPost.objects.filter(info__0__test='test').count(), 1)
+            BlogPost.objects.filter(info__exact='test').count(), 1)
+        self.assertEqual(
+            BlogPost.objects.filter(info__0__test='test').count(), 1)
 
         # Confirm handles non strings or non existing keys
-        self.assertEqual(BlogPost.objects.filter(info__0__test__exact='5').count(), 0)
+        self.assertEqual(
-        self.assertEqual(BlogPost.objects.filter(info__100__test__exact='test').count(), 0)
+            BlogPost.objects.filter(info__0__test__exact='5').count(), 0)
+        self.assertEqual(
+            BlogPost.objects.filter(info__100__test__exact='test').count(), 0)
         BlogPost.drop_collection()
 
     def test_list_field_passed_in_value(self):
@@ -951,7 +961,6 @@ class FieldTest(unittest.TestCase):
         foo.bars.append(bar)
         self.assertEqual(repr(foo.bars), '[<Bar: Bar object>]')
 
-
     def test_list_field_strict(self):
         """Ensure that list field handles validation if provided a strict field type."""
 
@@ -1082,20 +1091,28 @@ class FieldTest(unittest.TestCase):
         self.assertTrue(isinstance(e2.mapping[1], IntegerSetting))
 
         # Test querying
-        self.assertEqual(Simple.objects.filter(mapping__1__value=42).count(), 1)
+        self.assertEqual(
-        self.assertEqual(Simple.objects.filter(mapping__2__number=1).count(), 1)
+            Simple.objects.filter(mapping__1__value=42).count(), 1)
-        self.assertEqual(Simple.objects.filter(mapping__2__complex__value=42).count(), 1)
+        self.assertEqual(
-        self.assertEqual(Simple.objects.filter(mapping__2__list__0__value=42).count(), 1)
+            Simple.objects.filter(mapping__2__number=1).count(), 1)
-        self.assertEqual(Simple.objects.filter(mapping__2__list__1__value='foo').count(), 1)
+        self.assertEqual(
+            Simple.objects.filter(mapping__2__complex__value=42).count(), 1)
+        self.assertEqual(
+            Simple.objects.filter(mapping__2__list__0__value=42).count(), 1)
+        self.assertEqual(
+            Simple.objects.filter(mapping__2__list__1__value='foo').count(), 1)
 
         # Confirm can update
         Simple.objects().update(set__mapping__1=IntegerSetting(value=10))
-        self.assertEqual(Simple.objects.filter(mapping__1__value=10).count(), 1)
+        self.assertEqual(
+            Simple.objects.filter(mapping__1__value=10).count(), 1)
 
         Simple.objects().update(
             set__mapping__2__list__1=StringSetting(value='Boo'))
-        self.assertEqual(Simple.objects.filter(mapping__2__list__1__value='foo').count(), 0)
+        self.assertEqual(
-        self.assertEqual(Simple.objects.filter(mapping__2__list__1__value='Boo').count(), 1)
+            Simple.objects.filter(mapping__2__list__1__value='foo').count(), 0)
+        self.assertEqual(
+            Simple.objects.filter(mapping__2__list__1__value='Boo').count(), 1)
 
         Simple.drop_collection()
 
@@ -1141,12 +1158,16 @@ class FieldTest(unittest.TestCase):
         post.save()
 
         self.assertEqual(BlogPost.objects.count(), 3)
-        self.assertEqual(BlogPost.objects.filter(info__title__exact='test').count(), 1)
+        self.assertEqual(
-        self.assertEqual(BlogPost.objects.filter(info__details__test__exact='test').count(), 1)
+            BlogPost.objects.filter(info__title__exact='test').count(), 1)
+        self.assertEqual(
+            BlogPost.objects.filter(info__details__test__exact='test').count(), 1)
 
         # Confirm handles non strings or non existing keys
-        self.assertEqual(BlogPost.objects.filter(info__details__test__exact=5).count(), 0)
+        self.assertEqual(
-        self.assertEqual(BlogPost.objects.filter(info__made_up__test__exact='test').count(), 0)
+            BlogPost.objects.filter(info__details__test__exact=5).count(), 0)
+        self.assertEqual(
+            BlogPost.objects.filter(info__made_up__test__exact='test').count(), 0)
 
         post = BlogPost.objects.create(info={'title': 'original'})
         post.info.update({'title': 'updated'})
@@ -1207,19 +1228,26 @@ class FieldTest(unittest.TestCase):
         self.assertTrue(isinstance(e2.mapping['someint'], IntegerSetting))
 
         # Test querying
-        self.assertEqual(Simple.objects.filter(mapping__someint__value=42).count(), 1)
+        self.assertEqual(
-        self.assertEqual(Simple.objects.filter(mapping__nested_dict__number=1).count(), 1)
+            Simple.objects.filter(mapping__someint__value=42).count(), 1)
-        self.assertEqual(Simple.objects.filter(mapping__nested_dict__complex__value=42).count(), 1)
+        self.assertEqual(
-        self.assertEqual(Simple.objects.filter(mapping__nested_dict__list__0__value=42).count(), 1)
+            Simple.objects.filter(mapping__nested_dict__number=1).count(), 1)
-        self.assertEqual(Simple.objects.filter(mapping__nested_dict__list__1__value='foo').count(), 1)
+        self.assertEqual(
+            Simple.objects.filter(mapping__nested_dict__complex__value=42).count(), 1)
+        self.assertEqual(
+            Simple.objects.filter(mapping__nested_dict__list__0__value=42).count(), 1)
+        self.assertEqual(
+            Simple.objects.filter(mapping__nested_dict__list__1__value='foo').count(), 1)
 
         # Confirm can update
         Simple.objects().update(
             set__mapping={"someint": IntegerSetting(value=10)})
         Simple.objects().update(
             set__mapping__nested_dict__list__1=StringSetting(value='Boo'))
-        self.assertEqual(Simple.objects.filter(mapping__nested_dict__list__1__value='foo').count(), 0)
+        self.assertEqual(
-        self.assertEqual(Simple.objects.filter(mapping__nested_dict__list__1__value='Boo').count(), 1)
+            Simple.objects.filter(mapping__nested_dict__list__1__value='foo').count(), 0)
+        self.assertEqual(
+            Simple.objects.filter(mapping__nested_dict__list__1__value='Boo').count(), 1)
 
         Simple.drop_collection()
 
@@ -1477,6 +1505,375 @@ class FieldTest(unittest.TestCase):
         mongoed = p1.to_mongo()
         self.assertTrue(isinstance(mongoed['parent'], ObjectId))
 
+    def test_cached_reference_fields(self):
+        class Animal(Document):
+            name = StringField()
+            tag = StringField()
+
+        class Ocorrence(Document):
+            person = StringField()
+            animal = CachedReferenceField(
+                Animal, fields=['tag'])
+
+        Animal.drop_collection()
+        Ocorrence.drop_collection()
+
+        a = Animal(name="Leopard", tag="heavy")
+        a.save()
+
+        self.assertEqual(Animal._cached_reference_fields, [Ocorrence.animal])
+        o = Ocorrence(person="teste", animal=a)
+        o.save()
+
+        p = Ocorrence(person="Wilson")
+        p.save()
+
+        self.assertEqual(Ocorrence.objects(animal=None).count(), 1)
+
+        self.assertEqual(
+            a.to_mongo(fields=['tag']), {'tag': 'heavy', "_id": a.pk})
+
+        self.assertEqual(o.to_mongo()['animal']['tag'], 'heavy')
+
+        # counts
+        Ocorrence(person="teste 2").save()
+        Ocorrence(person="teste 3").save()
+
+        count = Ocorrence.objects(animal__tag='heavy').count()
+        self.assertEqual(count, 1)
+
+        ocorrence = Ocorrence.objects(animal__tag='heavy').first()
+        self.assertEqual(ocorrence.person, "teste")
+        self.assertTrue(isinstance(ocorrence.animal, Animal))
+
+    def test_cached_reference_field_decimal(self):
+        class PersonAuto(Document):
+            name = StringField()
+            salary = DecimalField()
+
+        class SocialTest(Document):
+            group = StringField()
+            person = CachedReferenceField(
+                PersonAuto,
+                fields=('salary',))
+
+        PersonAuto.drop_collection()
+        SocialTest.drop_collection()
+
+        p = PersonAuto(name="Alberto", salary=Decimal('7000.00'))
+        p.save()
+
+        s = SocialTest(group="dev", person=p)
+        s.save()
+
+        self.assertEqual(
+            SocialTest.objects._collection.find_one({'person.salary': 7000.00}), {
+                '_id': s.pk,
+                'group': s.group,
+                'person': {
+                    '_id': p.pk,
+                    'salary': 7000.00
+                }
+            })
+
+    def test_cached_reference_field_reference(self):
+        class Group(Document):
+            name = StringField()
+
+        class Person(Document):
+            name = StringField()
+            group = ReferenceField(Group)
+
+        class SocialData(Document):
+            obs = StringField()
+            tags = ListField(
+                StringField())
+            person = CachedReferenceField(
+                Person,
+                fields=('group',))
+
+        Group.drop_collection()
+        Person.drop_collection()
+        SocialData.drop_collection()
+
+        g1 = Group(name='dev')
+        g1.save()
+
+        g2 = Group(name="designers")
+        g2.save()
+
+        p1 = Person(name="Alberto", group=g1)
+        p1.save()
+
+        p2 = Person(name="Andre", group=g1)
+        p2.save()
+
+        p3 = Person(name="Afro design", group=g2)
+        p3.save()
+
+        s1 = SocialData(obs="testing 123", person=p1, tags=['tag1', 'tag2'])
+        s1.save()
+
+        s2 = SocialData(obs="testing 321", person=p3, tags=['tag3', 'tag4'])
+        s2.save()
+
+        self.assertEqual(SocialData.objects._collection.find_one(
+            {'tags': 'tag2'}), {
+                '_id': s1.pk,
+                'obs': 'testing 123',
+                'tags': ['tag1', 'tag2'],
+                'person': {
+                    '_id': p1.pk,
+                    'group': g1.pk
+                }
+        })
+
+        self.assertEqual(SocialData.objects(person__group=g2).count(), 1)
+        self.assertEqual(SocialData.objects(person__group=g2).first(), s2)
+
+    def test_cached_reference_field_update_all(self):
+        class Person(Document):
+            TYPES = (
+                ('pf', "PF"),
+                ('pj', "PJ")
+            )
+            name = StringField()
+            tp = StringField(
+                choices=TYPES
+            )
+
+            father = CachedReferenceField('self', fields=('tp',))
+
+        Person.drop_collection()
+
+        a1 = Person(name="Wilson Father", tp="pj")
+        a1.save()
+
+        a2 = Person(name='Wilson Junior', tp='pf', father=a1)
+        a2.save()
+
+        self.assertEqual(dict(a2.to_mongo()), {
+            "_id": a2.pk,
+            "name": u"Wilson Junior",
+            "tp": u"pf",
+            "father": {
+                "_id": a1.pk,
+                "tp": u"pj"
+            }
+        })
+
+        self.assertEqual(Person.objects(father=a1)._query, {
+            'father._id': a1.pk
+        })
+        self.assertEqual(Person.objects(father=a1).count(), 1)
+
+        Person.objects.update(set__tp="pf")
+        Person.father.sync_all()
+
+        a2.reload()
+        self.assertEqual(dict(a2.to_mongo()), {
+            "_id": a2.pk,
+            "name": u"Wilson Junior",
+            "tp": u"pf",
+            "father": {
+                "_id": a1.pk,
+                "tp": u"pf"
+            }
+        })
+
+    def test_cached_reference_fields_on_embedded_documents(self):
+        def build():
+            class Test(Document):
+                name = StringField()
+
+            type('WrongEmbeddedDocument', (
+                EmbeddedDocument,), {
+                    'test': CachedReferenceField(Test)
+            })
+
+        self.assertRaises(InvalidDocumentError, build)
+
+    def test_cached_reference_auto_sync(self):
+        class Person(Document):
+            TYPES = (
+                ('pf', "PF"),
+                ('pj', "PJ")
+            )
+            name = StringField()
+            tp = StringField(
+                choices=TYPES
+            )
+
+            father = CachedReferenceField('self', fields=('tp',))
+
+        Person.drop_collection()
+
+        a1 = Person(name="Wilson Father", tp="pj")
+        a1.save()
+
+        a2 = Person(name='Wilson Junior', tp='pf', father=a1)
+        a2.save()
+
+        a1.tp = 'pf'
+        a1.save()
+
+        a2.reload()
+        self.assertEqual(dict(a2.to_mongo()), {
+            '_id': a2.pk,
+            'name': 'Wilson Junior',
+            'tp': 'pf',
+            'father': {
+                '_id': a1.pk,
+                'tp': 'pf'
+            }
+        })
+
+    def test_cached_reference_auto_sync_disabled(self):
+        class Persone(Document):
+            TYPES = (
+                ('pf', "PF"),
+                ('pj', "PJ")
+            )
+            name = StringField()
+            tp = StringField(
+                choices=TYPES
+            )
+
+            father = CachedReferenceField(
+                'self', fields=('tp',), auto_sync=False)
+
+        Persone.drop_collection()
+
+        a1 = Persone(name="Wilson Father", tp="pj")
+        a1.save()
+
+        a2 = Persone(name='Wilson Junior', tp='pf', father=a1)
+        a2.save()
+
+        a1.tp = 'pf'
+        a1.save()
+
+        self.assertEqual(Persone.objects._collection.find_one({'_id': a2.pk}), {
+            '_id': a2.pk,
+            'name': 'Wilson Junior',
+            'tp': 'pf',
+            'father': {
+                '_id': a1.pk,
+                'tp': 'pj'
+            }
+        })
+
+    def test_cached_reference_embedded_fields(self):
+        class Owner(EmbeddedDocument):
+            TPS = (
+                ('n', "Normal"),
+                ('u', "Urgent")
+            )
+            name = StringField()
+            tp = StringField(
+                verbose_name="Type",
+                db_field="t",
+                choices=TPS)
+
+        class Animal(Document):
+            name = StringField()
+            tag = StringField()
+
+            owner = EmbeddedDocumentField(Owner)
+
+        class Ocorrence(Document):
+            person = StringField()
+            animal = CachedReferenceField(
+                Animal, fields=['tag', 'owner.tp'])
+
+        Animal.drop_collection()
+        Ocorrence.drop_collection()
+
+        a = Animal(nam="Leopard", tag="heavy",
+                   owner=Owner(tp='u', name="Wilson Júnior")
+                   )
+        a.save()
+
+        o = Ocorrence(person="teste", animal=a)
+        o.save()
+        self.assertEqual(dict(a.to_mongo(fields=['tag', 'owner.tp'])), {
+            '_id': a.pk,
+            'tag': 'heavy',
+            'owner': {
+                't': 'u'
+            }
+        })
+        self.assertEqual(o.to_mongo()['animal']['tag'], 'heavy')
+        self.assertEqual(o.to_mongo()['animal']['owner']['t'], 'u')
+
+        # counts
+        Ocorrence(person="teste 2").save()
+        Ocorrence(person="teste 3").save()
+
+        count = Ocorrence.objects(
+            animal__tag='heavy', animal__owner__tp='u').count()
+        self.assertEqual(count, 1)
+
+        ocorrence = Ocorrence.objects(
+            animal__tag='heavy',
+            animal__owner__tp='u').first()
+        self.assertEqual(ocorrence.person, "teste")
+        self.assertTrue(isinstance(ocorrence.animal, Animal))
+
+    def test_cached_reference_embedded_list_fields(self):
+        class Owner(EmbeddedDocument):
+            name = StringField()
+            tags = ListField(StringField())
+
+        class Animal(Document):
+            name = StringField()
+            tag = StringField()
+
+            owner = EmbeddedDocumentField(Owner)
+
+        class Ocorrence(Document):
+            person = StringField()
+            animal = CachedReferenceField(
+                Animal, fields=['tag', 'owner.tags'])
+
+        Animal.drop_collection()
+        Ocorrence.drop_collection()
+
+        a = Animal(nam="Leopard", tag="heavy",
+                   owner=Owner(tags=['cool', 'funny'],
+                               name="Wilson Júnior")
+                   )
+        a.save()
+
+        o = Ocorrence(person="teste 2", animal=a)
+        o.save()
+        self.assertEqual(dict(a.to_mongo(fields=['tag', 'owner.tags'])), {
+            '_id': a.pk,
+            'tag': 'heavy',
+            'owner': {
+                'tags': ['cool', 'funny']
+            }
+        })
+
+        self.assertEqual(o.to_mongo()['animal']['tag'], 'heavy')
+        self.assertEqual(o.to_mongo()['animal']['owner']['tags'],
+                         ['cool', 'funny'])
+
+        # counts
+        Ocorrence(person="teste 2").save()
+        Ocorrence(person="teste 3").save()
+
+        query = Ocorrence.objects(
+            animal__tag='heavy', animal__owner__tags='cool')._query
+        self.assertEqual(
+            query, {'animal.owner.tags': 'cool', 'animal.tag': 'heavy'})
+
+        ocorrence = Ocorrence.objects(
+            animal__tag='heavy',
+            animal__owner__tags='cool').first()
+        self.assertEqual(ocorrence.person, "teste 2")
+        self.assertTrue(isinstance(ocorrence.animal, Animal))
+
     def test_objectid_reference_fields(self):
 
         class Person(Document):
@@ -1836,7 +2233,6 @@ class FieldTest(unittest.TestCase):
         self.assertEqual(repr(Person.objects(city=None)),
                          "[<Person: Person object>]")
 
-
     def test_generic_reference_choices(self):
         """Ensure that a GenericReferenceField can handle choices
         """
@@ -1982,7 +2378,8 @@ class FieldTest(unittest.TestCase):
         attachment_required.blob = Binary(b('\xe6\x00\xc4\xff\x07'))
         attachment_required.validate()
 
-        attachment_size_limit = AttachmentSizeLimit(blob=b('\xe6\x00\xc4\xff\x07'))
+        attachment_size_limit = AttachmentSizeLimit(
+            blob=b('\xe6\x00\xc4\xff\x07'))
         self.assertRaises(ValidationError, attachment_size_limit.validate)
         attachment_size_limit.blob = b('\xe6\x00\xc4\xff')
         attachment_size_limit.validate()
@@ -2179,7 +2576,6 @@ class FieldTest(unittest.TestCase):
         c = self.db['mongoengine.counters'].find_one({'_id': 'person.id'})
         self.assertEqual(c['next'], 1000)
 
-
     def test_sequence_field_get_next_value(self):
         class Person(Document):
             id = SequenceField(primary_key=True)
@@ -2368,7 +2764,6 @@ class FieldTest(unittest.TestCase):
         self.assertEqual(1, post.comments[0].id)
         self.assertEqual(2, post.comments[1].id)
 
-
     def test_generic_embedded_document(self):
         class Car(EmbeddedDocument):
             name = StringField()