Ionel Cristian: Tweaks for making django admin faster

Here follow a number of tricks I’ve employed in the past to make django admin faster.

Editable foreign keys in the changelist

If you have foreign keys in list_editable django will make 1 database query for each item in the changelist. Quite a lot for a changelist of 100 items. The trick is to cache the choices for that formfield:

class MyAdmin(admin.ModelAdmin):
    list_editable = 'myfield',
    def formfield_for_dbfield(self, db_field, **kwargs):
        request = kwargs['request']
        formfield = super(MyAdmin, self).formfield_for_dbfield(db_field, **kwargs)
        if db_field.name == 'myfield':
            myfield_choices_cache = getattr(request, 'myfield_choices_cache', None)
            if myfield_choices_cache is not None:
                formfield.choices = myfield_choices_cache
            else:
                request.myfield_choices_cache = formfield.choices
        return formfield

Foreign keys or many to many fields in admin inlines

If you have fk of m2m fields on InlineModelAdmin for every object in the formset you’ll get a database hit. You can avoid this by having something like:

class MyAdmin(admin.TabularInline):
    fields = 'myfield',
    def formfield_for_dbfield(self, db_field, **kwargs):
        formfield = super(MyAdmin, self).formfield_for_dbfield(db_field, **kwargs)
        if db_field.name == 'myfield':
            # dirty trick so queryset is evaluated and cached in .choices
            formfield.choices = formfield.choices
        return formfield

Enable template caching

It’s amazing how easy it is to forget to add this in your settings:

TEMPLATE_LOADERS = (
    ('django.template.loaders.cached.Loader', (
        'django.template.loaders.filesystem.Loader',
        'django.template.loaders.app_directories.Loader',
    )),
)

Use select_related for the edit forms too

In case you have some readonly fields on the edit form and they need related data to display list_select_related doesn’t help. Eg:

class MyAdmin(admin.ModelAdmin):
    readonly_fields = 'myfield',
    def queryset(self, request):
        return super(MyAdmin, self).queryset(request).select_related('myfield')

Use annotations if possible for function entries list_display instead of making additional queries

Check the aggregation api to see if you can use this. Here’s the typical example:

class AuthorAdmin(admin.ModelAdmin):
    list_display = 'books_count',
    
    def books_count(self, obj):
        return obj.books_count
    
    def queryset(self, request):
        return super(AuthorAdmin, self).queryset(
            request).annotate(books_count=Count('books'))

The models would look like this:

class Author(models.Model):
    name = models.CharField(max_length=100)

class Book(models.Model):
    name = models.CharField(max_length=100)
    author = models.ForeignKey(Author, related_name="books")

Cache the filters from the admin changelist

This has the obvious tradeoff that you’ll have stale data in the list of filter but if they don’t change that often and those distinct queries are killing your database then this will help a lot. Just add a custom change_list.html template in your project (eg: templates/<myapp>/change_list.html):

{% extends "admin/change_list.html" %}
{% load admin_list i18n cache %}

{% block filters %}
    {% cache 300 admin_filters request.GET.items request.path request.user.username %}
        {% if cl.has_filters %}
          <div id="changelist-filter">
            <h2>{% trans 'Filter' %}</h2>
            {% for spec in cl.filter_specs %}{% admin_list_filter cl spec %}{% endfor %}
          </div>
        {% endif %}
    {% endcache %}
{% endblock %}

Bonus trick

frame = sys._getframe(1)
while frame:
    if frame.f_code.co_name == 'render_change_form':
        if 'request' in frame.f_locals:
            request = frame.f_locals['request']
            break
    frame = frame.f_back
else:
    raise RuntimeError("Could not find request object.")

# do stuff with request

This could be used in some specific cases (eg: you need the request in a widget’s render method), as a last resort ofcourse ;)

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What did you do to make django admin faster ?

Tagged: django, django admin, python