Django admin performance issue

Question

I'm getting thousands of these queries when I try to open up a model in the Django admin interface and it's leading to a serious performance issue.

[sql] SELECT ... FROM `auth_user` WHERE `auth_user`.`id` = 9535
[sql] (21ms) Found 1 matching rows
[sql] SELECT ... FROM `auth_user` WHERE `auth_user`.`id` = 9536
[sql] (20ms) Found 1 matching rows

Any ideas why Django admin isn't using select_related()?

Here are (I think) the relevant parts of the model (I'm looking at an instance of the Student model in the admin):

from django.contrib.auth.models import User

class Student(models.Model):
    user = models.OneToOneField(User, unique=True)
    mhtl_user = models.OneToOneField(MHTLUser, unique=True)
    def __str__(self):
        return u"%s %s" % (self.user.first_name, self.user.last_name)

class MHTLUser(models.Model):
    user = models.OneToOneField(User, unique=True)
    def __str__(self):
        return str(self.user)

Shifflett

Still experimenting -- just discovered if I comment out "mhtl_user = models.OneToOneField(MHTLUser, unique=True)" the queries go away. So it's related to that somehow... – Shifflett

Aaand it's the str function in MHTLUser. If that is gone, problem solved. But I'm still curious why that's an issue though. – Shifflett

What are you using to show the SQL queries like this ? – Rootless

github.com/dcramer/django-devserver =) – Shifflett

Not directly related to your problem but can I ask you why you define __str__ instead of __unicode__? Not mentioning that your Student __str__ return unicode... – Ultann

Short answer is that I don't really understand character encodings, or how Python deals with them, and I think there was some issue with "ordinal not in range" with ascii where str was being called. Rather than change the library that called str, it seemed easier to just return unicode. Lol, that's probably terrible, and thanks for making me realize I should probably learn these things. – Shifflett

Answer 1

Or just enable list_select_related.

class MyModelAdmin(admin.ModelAdmin):
    list_select_related = True
    # ....

Flyaway

I originally accepted this answer because I thought it worked, but it was actually another change that fixed it, not this. I had commented the str method in MHTLUser. Using this ModelAdmin doesn't actually help in this case. – Shifflett

Answer 2

You could make Django use select_related by defining your own ModelAdmin like this

class MyModelAdmin(admin.ModelAdmin):
    def queryset(self, request):
        qs = super(MyModelAdmin, self).queryset(request)
        return qs.select_related()

Griselgriselda