Django model inheritance: how to retrieve records?

Question

I have these Django models:

class Base(models.Model):
    name = models.CharField(max_length=255)

class Restaurant(Base):
    pass

class Hotel(Base)
    pass

class Message(models.Model)
    text = models.TextField()
    parent = models.ForeignKey(Base, on_delete=models.CASCADE)

I would like to set up a query to retrieve all of the messages left about Hotels only. But how to do that?

Message.objects.filter(has_attr("Hotel"))

Obviously this doesn't work but something like that is what I am looking for.

Answer 1

An inherited model has an implicit OneToOneField from the child to the parent. This relation in reverse has, by default, as related name the name of the class, so hotel .

We thus can check if there exists a Hotel object for the given parent with:

Message.objects.filter()