How to make reverse relationship query with count in Django

Question

I have related models as defined below. I want to write a query to get all product that have product_options. I there a way I can achieve this or how to my attempted solution. I have pasted my solution below.

# Attempted Solution

Product.objects.filter(product_options__count__gt=0)

# Defined models

class Product(models.Model):
    name = models.CharField(max_length=200)


class ProductOption(models.Model):
    name = models.CharField(max_length=200)
    product = models.ForeignKey(
        Product,
        on_delete=models.PROTECT,
        related_name='product_options'
    )

user_67579 · Answer

You can work with a .annotate() [Django-doc] and then .filter(…) [Django-doc]:

from django.db.models import Count

Product.objects.annotate(
    noptions=Count('product_options')
).filter(
    noptions__gt=0
)

Since django-3.2, you can also work with .alias(…) [Django-doc]:

from django.db.models import Count

Product.objects.alias(
    noptions=Count('product_options')
).filter(
    noptions__gt=0
)

user_5048203 · Answer

You can easily do it by this query

Product.objects.filter(product_options__isnull=False)

It will send those product that doesn't have product options

How to make reverse relationship query with count in Django

2 Answers