I have a database, which among others has the following tables:
CREATE TABLE users (
userId BIGINT PRIMARY KEY
);
CREATE TABLE movies (
movieId BIGINT PRIMARY KEY,
title varchar(255) NOT NULL
);
CREATE TABLE ratings (
userId BIGINT NOT NULL REFERENCES users(userId),
movieId BIGINT NOT NULL REFERENCES movies(movieId),
rating SMALLINT NOT NULL,
timestamp varchar(150) NOT NULL,
CONSTRAINT unique_userid_movieid UNIQUE(userId, movieId)
);
As you can see the 'rating' table has no separate primary key field.
Here are the models created by Django with some my corrections:
class Users(models.Model):
userid = models.BigIntegerField(primary_key=True)
def __unicode__(self):
return u"User %d" % self.userid
class Meta:
db_table = u'users'
class Movies(models.Model):
movieid = models.BigIntegerField(primary_key=True)
title = models.CharField(max_length=255)
users = models.ManyToManyField(Users, through='Ratings',
related_name="rated_movies")
def __unicode__(self):
return self.title
class Meta:
db_table = u'movies'
class Ratings(models.Model):
user = models.ForeignKey(Users, db_column='userid')
movie = models.ForeignKey(Movies, db_column='movieid')
rating = models.SmallIntegerField()
timestamp = models.BigIntegerField()
def __unicode__(self):
return u"%d" % self.rating
class Meta:
db_table = u'ratings'
unique_together = (("user", "movie"),)
So having these models i can do this:
In [1]: from django_orm.movielens.models import *
In [2]: u = Users.objects.get(pk=1)
In [3]: u.rated_movies.all()
Out[3]: [<Movies: Boomerang (1992)>,..]
or this:
In [4]: m = Movies.objects.get(pk=1)
In [5]: m.users.all().count()
Out[5]: 2264
But i can't get the "ratings" objects because trying this:
Ratings.objects.filter(user=1)
or this:
u.ratings_set.all()
causes the following error
DatabaseError: column ratings.id does not exist
LINE 1: SELECT "ratings"."id", "ratings"."userid",
"ratings"."moviei...
Is there a way to tell Django, that 'Ratings' models does not have a
separate primary key? Or my only option is to add the column to the
'ratings' table?
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