But, Why is the Admin Slow?

DjangoCon 2015 Talk

Transcript

1. BUT, WHY IS THE ADMIN SLOW? Jacinda Shelly DjangoCon 2015
2. ABOUT ME • Platform Engineer at Doctor On Demand • Been using Django for 4+ years • Given two tutorials on the admin • Second time speaking at DjangoCon • Love reading and rowing
3. SO, YOU JUST STARTED USING THE ADMIN
4. FIRST, YOU FEEL LIKE THIS
6. THEN PEOPLE START USING IT
8. BUT THEN…
10. AND NOW YOU’RE DEALING WITH…
12. A LIBRARY
14. class LibraryUser(AbstractUser): ''' Custom user for our library project. Inherits from AbstractUser, which has the following fields: - username - first_name - last_name - email - is_staff - is_active - date_joined ''' birthdate = models.DateField('Date of Birth', null=True, blank=False) gender = models.CharField('Gender', max_length=1, choices=GENDER_CHOICES, blank=False) books = models.ManyToManyField('stacks.Book', through='stacks.LoanedBook') def __unicode__(self): return self.get_full_name()
15. class Author(models.Model): last_name = models.CharField(max_length=32) first_name = models.CharField(max_length=32) def __unicode__(self): return self.full_name()
16. class Book(AbstractItem): authors = models.ManyToManyField(Author, related_name='works') page_count = models.PositiveIntegerField() title = models.CharField(max_length=4000) daily_fine = models.DecimalField( max_digits=4, decimal_places=2, default='0.25', help_text=_("Amount the patron will be fined per day for an overdue library book")) def __unicode__(self): return self.title
17. class LoanedBook(models.Model): patron = models.ForeignKey(settings.AUTH_USER_MODEL) book = models.ForeignKey(Book) checkout_date = models.DateField() due_date = models.DateField() return_date = models.DateField(null=True, blank=True) times_renewed = models.IntegerField(default=0) fine_paid = models.NullBooleanField() def __unicode__(self): return ': '.join([str(self.patron), str(self.book)])
18. https://github.com/django-debug-toolbar/ django-debug-toolbar INSTALLED_APPS = ( # … 'debug_toolbar' )
19. Quick Tip! * INTERNAL_IPS is a whitelist of IPs making requests to your server
23. def __unicode__(self): return ': '.join([str(self.patron), str(self.book)]) Problem: Solution 1: @admin.register(LoanedBook) class LoanedBookAdmin(admin.ModelAdmin): list_display = ('patron', 'book') Solution 2a: @admin.register(LoanedBook) class LoanedBookAdmin(admin.ModelAdmin): list_select_related = True Solution 2b: @admin.register(LoanedBook) class LoanedBookAdmin(admin.ModelAdmin): list_select_related = ('patron', 'book')
25. @admin.register(LoanedBook) class LoanedBookAdmin(admin.ModelAdmin): list_select_related = ('patron',) Let’s Try:
28. @admin.register(LoanedBook) class LoanedBookAdmin(admin.ModelAdmin): list_select_related = (‘patron’, ‘book') Full Solution 2b:
30. @admin.register(LoanedBook) class LoanedBookAdmin(admin.ModelAdmin): list_select_related = ('patron', 'book') def get_queryset(self, request): qs = super(LoanedBookAdmin, self).get_queryset(request) qs = qs.only('patron__first_name', ‘patron__last_name', 'book__daily_fine') return qs Well, let’s see…
33. @admin.register(LoanedBook) class LoanedBookAdmin(admin.ModelAdmin): list_select_related = ('patron', 'book') def get_queryset(self, request): qs = super(LoanedBookAdmin, self).get_queryset(request) qs = qs.only('patron__first_name', ‘patron__last_name', 'book__title') return qs Fixed!
35. Now, we want to try something else # models.py class Book(AbstractItem): authors = models.ManyToManyField(Author, related_name='works') def authors_display(self): return '; '.join([str(author) for author in self.authors.all()]) # admin.py @admin.register(Book) class BookAdmin(admin.ModelAdmin): list_display = ('__unicode__', 'authors_display') list_select_related = True
38. Solution @admin.register(Book) class BookAdmin(admin.ModelAdmin): list_display = ('__unicode__', 'authors_display') def get_queryset(self, request): qs = super(BookAdmin, self).get_queryset(request) qs = qs.prefetch_related('authors') return qs
41. Next Up - Counting! # models.py class Author(models.Model): def book_count(self): return self.works.count() # admin.py @admin.register(Author) class AuthorAdmin(admin.ModelAdmin): fields = ('first_name', 'last_name') list_display = ('__unicode__', 'book_count')
43. Custom Querysets to the Rescue (again)! from django.db.models import Count @admin.register(Author) class AuthorAdmin(admin.ModelAdmin): fields = ('first_name', 'last_name') list_display = ('__unicode__', 'book_count') def get_queryset(self, request): qs = super(AuthorAdmin, self).get_queryset(request) qs = qs.annotate(book_count=Count('works')) return qs
46. Side Note # models.py class Author(models.Model): def book_count(self): return self.works.count() book_count.admin_order_field = 'book_count'
47. A FEW RANDOM NOTES Decrease ModelAdmin.list_per_page Set ModelAdmin.show_full_result_count to False Remove pagination
48. THANK YOU @jacindashelly jshelly@doctorondemand.com