Question

I have these data models in django:

class User(models.Model):
     type = models.CharField()

class Tmp1(models.Model):
     var1 = models.ForeignKey(User)

class Tmp2(models.Model):
     var2 = models.ForeignKey(Tmp1)

class Tmp3(models.Model):
     user = models.ForeignKey(User)
     var3 = models.ForeignKey(Tmp2)

I want to have a Tmp3 queryset which selects instances of Tmp3 which Tmp3.var3.var2.var1.id equals Tmp3.user.id.

I know how I should do it with InnerJoin in PostgreSQL but I don’t know how to do it with Django queryset.

Answer 1

From what I understand you want to get Tmp3 objects in which their user attribute matches the related user in the Tmp1 table (for the current Tmp3 object) – it sounds like you can make use of F expressions

from django.db.models import F
Tmp3.objects.filter(var3__var2__var1=F('user'))