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)

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... — Charles Offenbacher, Mar 15 '12 at 12:35
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. — Charles Offenbacher, Mar 15 '12 at 12:37
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... — Etienne, Mar 16 '12 at 01:57
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. — Charles Offenbacher, Mar 16 '12 at 12:30

score 3 · Accepted Answer · answered Mar 15 '12 at 13:31

3

Or just enable list_select_related.

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

answered Mar 15 '12 at 13:31

jpic

32,891
5
112
113

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. – Charles Offenbacher Mar 16 '12 at 00:10

score 2 · Answer 2 · answered Mar 15 '12 at 12:37

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()

answered Mar 15 '12 at 12:37

Juho

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5
9

Django admin performance issue

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