Question

I have 3 models in django:

class Movie(models.Model):
    mid = models.IntegerField(primary_key = True)
    name = models.CharField(max_length = 100)

class User(models.Model):
    username = models.CharField(max_length=128, null=True)
    uid = models.CharField(max_length=100)
    movie = models.ManyToManyField(Movie, through = "Vote")

class Vote(models.Model):
    movie = models.ForeignKey(Movie)
    user = models.ForeignKey(User)
    rating = models.IntegerField()

here rating = 0/1, 0 means dislike, 1 means like
i want to make some queries using filters:

1. find out all movies that a current user likes. For that i use this following 2 queries, but none of them work. In both cases it gives erroneous results

   ans = Movie.objects.filter(vote__user = self).filter(vote__rating = 1)

   ans = Movie.objects.filter(user__uid = self.uid).filter(vote__rating = 1)

2. I have a list of users in an array ids. I want to find out how many users from this list like a particular movie?
   i tried this, but this is also incorrect:

   ret = User.objects.filter(uid__in = ids).filter(vote__movie = mov).filter(vote__rating = 1)

can somebody please help me with these 2 queries?

Answer 1

I’d also suggest letting django assign the model’s id’s but if you are using a legacy database or for some other reason need to assign the id’s you can query like so:

1. # uid is some uid
   user = User.objects.get(uid=uid)
   likes = Movie.objects.filter(vote__user=user, vote__rating=1)
   

   or

   likes = Movie.objects.filter(vote__user__uid=some_uid, vote__rating=1)
   

2. count of people in the list of users who like a specific movie:

   >>> uids = ['1','2','3']
   >>> # if mov is a Movie instance
   >>> votes = Vote.objects.filter(user__uid__in=uids, movie=mov, rating=1)
   >>> print votes.query
   SELECT "so1_vote"."id", "so1_vote"."movie_id", "so1_vote"."user_id", "so1_vote"."rating" FROM "so1_vote" INNER JOIN "so1_user" ON ("so1_vote"."user_id" = "so1_user"."id") WHERE ("so1_user"."uid" IN (1, 2, 3) AND "so1_vote"."movie_id" = 1  AND "so1_vote"."rating" = 1 )
   >>> # if mov is a mid for a movie
   >>> # get movie instance by using Movie.objects.get(mid=mov)
   >>> # or query:
   >>> # votes = Vote.objects.filter(user__uid__in=uids, movie__mid=mov, rating=1)
   >>> likes_count = votes.count()
   >>> print likes_count
   0
   

   combined:

   likes_count = Votes.objects.filter(user__uid__in=uids, movie=mov, rating=1).count()