Question

Hi Stackoverflow people,

I am experiencing a strange issue with a select_related query in Django. I have installed the django-cities app, which lists geo information for a large number of cities.
In my project model, I have created a foreignkey to the city element to store the location in my models.py.

from cities.models import City 
class Project(models.Model): 
   ...
   city = models.ForeignKey(City, blank = True, null = True)

Due to the large number of possible cities, I have created a query in my class based view which selects the related city field when creating a Project object.

from django.views.generic.edit import CreateView, UpdateView, DeleteView
from project.models import Project
class ProjectCreate(CreateView):
    queryset = Project.objects.select_related('city__country', 'city__region').all()
    template_name = 'solution/solution_create_form.html'

However, when I request the ProjectCreate class, Django still pulls an endless number of foreignkeys from the database. The logger is showing an unlimited number of the following requests.

…
DEBUG (0.000) SELECT “cities_region”.”id”, “cities_region”.”name”,
“cities_region”.”slug”, “cities_region”.”name_std”,
“cities_region”.”code”, “cities_region”.”country_id” FROM
“cities_region” WHERE “cities_region”.”id” = 3861887 ; args=(3861887,)
DEBUG (0.000) SELECT “cities_country”.”id”, “cities_country”.”name”,
“cities_country”.”slug”, “cities_country”.”code”,
“cities_country”.”population”, “cities_country”.”continent”,
“cities_country”.”tld” FROM “cities_country” WHERE
“cities_country”.”id” = 3865483 ; args=(3865483,) D
…

How can I force the select related method when I execute the ProjectCreate class?

Thank you for your help and suggestions!

Answer 1

Without any testing, have you tried overriding the get_queryset method instead of using the queryset attribute? At least you will be more flexible with exception catching and other techniques.