将原始sql映射到django orm

有没有办法简化这个工作代码? 这段代码为一个对象获取所有不同的投票类型,可能有20种,并对每种类型进行计数。 我不喜欢编写原始sql,而是使用orm。这有点棘手,因为我在模型中使用了通用外键。

def get_object_votes(self, obj):
    """ 
    Get a dictionary mapping vote to votecount
    """
    ctype = ContentType.objects.get_for_model(obj)

    cursor = connection.cursor()
    cursor.execute("""
       SELECT v.vote , COUNT(*)
       FROM votes v
       WHERE %d = v.object_id AND %d = v.content_type_id
       GROUP BY 1
       ORDER BY 1 """ % ( obj.id, ctype.id )
    )
    votes = {}

    for row in cursor.fetchall():
       votes[row[0]] = row[1]

    return votes

class Vote(models.Model):
    user = models.ForeignKey(User)

    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    payload = generic.GenericForeignKey('content_type', 'object_id')

    vote = models.IntegerField(choices = possible_votes.items() )


class Issue(models.Model):
    title = models.CharField( blank=True, max_length=200)