mongodb - mongoengine NotUniqueError on empty collection -

i trying save first object collection (i did db.connection.drop_database() ensure first object), keep getting *** notuniqueerror: tried save duplicate unique keys error.

here's quick example of get:

ipdb> card.objects.all()   []   ipdb> card   `<card: <card url/pk: c569e1c9-7311-441e-ba03-0e86d4bc2932>>`   ipdb> card.save()   *** notuniqueerror: tried save duplicate unique keys (e11000 duplicate key error index: contacts.dav_object.$username_1  dup key: { : null })   ipdb> card.drop_collection()   ipdb> card.save()   `<card: <card url/pk: c569e1c9-7311-441e-ba03-0e86d4bc2932>>`   ipdb> 

i'm using unittest, , setup method has card.ensure_indexes(). suspect has it, without line mongo accept duplicated entries, if model definition says unique=true.

if add card._collection.drop_indexes() after card.ensure_indexes() problem goes away, duplicated entries, said above.

here's card model:

class card(davobject):       addressbook = db.referencefield("addressbook")       url = db.stringfield(required=true, unique=true, unique_with=["addressbook", "url"])       active = db.booleanfield(default=true)       text = db.stringfield(required=true)   

and here's davobject:

class davobject(db.document):     meta = {         'allow_inheritance': true,     }      last_update = db.complexdatetimefield(required=true, default=datetime.utcnow)      def __unicode__(self):         return u"<%s url/pk: %s>" % (self.__class__.__name__, getattr(self, "url", self.pk))      def save(self, *args, **kwargs):         if self._get_changed_fields():             self.last_update = datetime.utcnow()         return db.document.save(self, *args, **kwargs) 

i can't figure out what's wrong.

i'm using mongoengine 0.8.3, flask 0.10.1 , python 2.7.3.

look problem inheritance: set 'allow_inheritance': true davobject means inherited models store in 1 collection.

you have username index model inherited davobject , have conflict when trying insert 2 inherited davobject documents same username (none).

if not shure need use 'allow_inheritance': true set false or try put documents different indexes separate collections.

to check assumption try print list(davobject.objects.all()).