Question

class AppUser(models.Model):
    user = models.ForeignKey(User, unique=True)
    slug = models.SlugField(editable=False, blank=True)

For above model suppose we have a object “appuser” which we have rendered in template

Does django hits User db each time when we use it like appuser.user.username in our code??

Any help on how in django/python db lookups are done while accessing foreign key and many-to-many variables ??

Answer 1

You should carefully read through this for all details to database access optimization: https://docs.djangoproject.com/en/1.3/topics/db/optimization/

And select_related():

https://docs.djangoproject.com/en/dev/ref/models/querysets/#select-related

As for a quick answer to your question: It depends on how you’ve retrieved the object

With

appuser = AppUser.objects.get(pk=id)

it will hit the database separately for appuser.user.

But with

appuser = AppUser.objects.select_related().get(pk=id)

It will do a joined query, so accessing appuser.user does not trigger an SQL query.