mongoengine search in EmbeddedDocument ListField

Question

I use django-mongonengine to use a mongdb database; and i got a question about filtering/searching inside a structure like this:

class Shop(Document):
created = DateTimeField(default=datetime.now,verbose_name='date_created')
updated = DateTimeField(default=datetime.now,verbose_name='date_updated')
code = StringField(required=True,unique=True)
socialName = StringField(verbose_name='legal_name')
name = StringField(required=True,verbose_name='shop_name')
address = StringField(required=True,verbose_name='shop_address')
gpsLoc = GeoPointField()
apdo = IntField(default=0)
logo = StringField(verbose_name='url_logo')
listGifts = ListField(EmbeddedDocumentField(Gift))
listOffers = ListField(EmbeddedDocumentField(Offer))
def __unicode__(self):
    return u'%s' % (self.name)
@queryset_manager
def objects(doc_cls,queryset):
    return queryset.order_by('-shop_name')


class Gifted(EmbeddedDocument):
    created = DateTimeField(default=datetime.now,verbose_name='date_created')
    gifted = DateTimeField(default=datetime.now,verbose_name='date_gifted')
    shop = ReferenceField(Shop,required=True,verbose_name='shop')
    gift = EmbeddedDocumentField(Gift,required=True,verbose_name='gift')
    def __unicode__(self):
        return u'%s' % (self.gift)
    @queryset_manager
    def objects(doc_cls,queryset):
        return queryset.order_by('-date_gifted')




class UserProfile(EmbeddedDocument):
    created = DateTimeField(default=datetime.now,verbose_name='date_created')
    updated = DateTimeField(default=datetime.now,verbose_name='date_updated')
    birthday = DateTimeField(verbose_name='birthday')
    gender = BooleanField(default=True,verbose_name='is_man')
    rel_status = StringField()
    name = StringField(max_length=50,verbose_name='name')
    phone = StringField(verbose_name='phone')
    points = IntField(default=0,verbose_name='current_points')
    listGifts = ListField(EmbeddedDocumentField(Gifted))
    listOffers = ListField(EmbeddedDocumentField(Discount))
    def __unicode__(self):      return self.name
    @queryset_manager
    def objects(doc_cls,queryset):
        return queryset.order_by('update')



class User(Document):
    username = EmailField(unique=True,max_length=250,min_length=4,required=True)
    password = StringField(max_length=100,required=True)
    created = DateTimeField(default=datetime.now,verbose_name='date_created')
    code = StringField(required=True,unique=True)
    tok_crypt = StringField(verbose_name='token_crypt',required=True)
    expired = DateTimeField(verbose_name='date_expired')
    last_login = DateTimeField(default=datetime.now, verbose_name='date_last_login')
    profile = EmbeddedDocumentField(UserProfile, verbose_name='profile')
    def __unicode__(self):  return self.username
    @queryset_manager
    def objects(doc_cls,queryset):
        return queryset.order_by('username')

If i want to search all the users that have some Gifted items from a particulary shop (Shop.code) how can i filter/search without using for inside for, inside for... etc.

Something like:

listUsers = User.objects(profile.listGifts__contains=Gifted.objects(shop.code=sCode))

listUsers = User->Profile->List(Gifted->Shop.code=code)

Answer 1

First you have to obtain the shop with the given code:

shop = Shop.objects(code=code)[0]

Then you use it to search inside your User collection:

listUsers = User.objects(profile__listGifts__shop=shop)

MongoEngine syntax for searching in lists is simple like that: you just write the query as if listGifts wasn't a list, and it will queries all the users whose list listGifts contains the given shop.

What MongoEngine doesn't do is joins. By that I mean that you cannot make a single query to more than one collection. The first query above belongs to the Shop class collection. The second one to the User class collection - UserProfile and Gifted are embedded documents in the same collection.