Please help me I've been stuck on this for way too long :(

What I want to do:

I have these two models:

class Specialization(models.Model):    name = models.CharField("name", max_length=64)class Doctor(models.Model):    name = models.CharField("name", max_length=128)    # ...    specialization = models.ForeignKey(Specialization)

I would like to annotate all specializations in a queryset with the number of doctors that have this specialization.

My Solution so Far:

I went through a loop and I made a simple: Doctor.objects.filter(specialization=spec).count() however this proved to be too slow and inefficient. The more I've read the more I realized that it would make sense to use a SubQuery here to filter the doctors for the OuterRef specialization. This is what I came up with:

doctors = Doctor.objects.all().filter(specialization=OuterRef("id")) \    .values("specialization_id") \    .order_by()add_doctors_count = doctors.annotate(cnt=Count("specialization_id")).values("cnt")[:1]spec_qs_with_counts = Specialization.objects.all().annotate(    num_applicable_doctors=Subquery(add_doctors_count, output_field=IntegerField()))

The output I get is just 1 for every speciality. The code just annotates every doctor object with its specialization_id and then annotates the count within that group, meaning it will be 1.

This doesn't make complete sense to me unfortunately. In my initial attempt I used an aggregate for the count, and while it works on its own it doesn't work as a SubQuery, I get this error:

This queryset contains a reference to an outer query and may only be used in a subquery.

I posted this question before and someone suggested doing Specialization.objects.annotate(count=Count("doctor"))

However this doesn't work because I need to count a specific queryset of Doctors.

I've followed these links

However, I'm not getting the same result:

• https://docs.djangoproject.com/en/1.11/ref/models/expressions/

• https://medium.com/@hansonkd/the-dramatic-benefits-of-django-subqueries-and-annotations-4195e0dafb16

• Django 1.11 Annotating a Subquery Aggregate

If you have any questions that would make this clearer please tell me.