Get sublcass queryset only

[KekeliDev]

I can't get queryset for a particular subclass only. I want to get only products relating that subclass only

• Django Model Utils version: 4.3.1
• Django version: 4.1
• Python version: 3.9

class Product(models.Model)
...
objects  = InheritanceManager()


class Phone(Product)
...

class Laptop(Product)
...

How do I get querysets for the subclass Phone without any other subclasses instances
I have gone through the documentation and didn't find any

I have built a custom filter that can do but it means I don't need the package and my concern is scalability of the custom implementation. I want to know if the package can help so I don't have to reinvent the wheel.

[kezabelle]

It's been a long time since I used the InheritanceManager, but I would think:

Product.objects.select_subclasses(Phone).filter(phone__isnull=False)

or something ought to do the trick. The select_subclasses would leave you with a heterogenous queryset of Product and Phone instances, so you'd subsequently want to only have Phone instances, which you'd get by filtering out rows which don't have a product → phone relation.

---

That said. If you're after a homogenous queryset, why not just do:

Phone.objects.filter(...)

and ignore the inheritance part entirely? It'll effectively be roughly the same query and without the additional complexity.

[KekeliDev]

Thank you very much this should work.
The trick I created earlier wouldn't scale very well as I have to load all products objects then load all Phone objects and use phone objects ids to do conditional check with if statements and even check for product status too.

I will use your suggestion even though I have embed category field in the product which are basically the subclasses so that I can filter on categories and no need to worry about subclassing.
I will adopt your suggestions because I want the database to handle queries not python functions