how to add annotate data in django-rest-framework queryset responses?

by

The accepted solution will hit the database as many times as results are returned. For each result, a count query to the database will be made.

The question is about adding annotations to the serializer, which is way more effective than doing a count query for each item in the response.

A solution for that:

models.py

class Author(models.Model):
    name = models.CharField(...)
    other_stuff = models...
    ...

class Book(models.Model):
    author = models.ForeignKey(Author)
    title = models.CharField(...)
    publication_year = models...
    ...

serializers.py

class BookSerializer(serializers.ModelSerializer):
    authors = serializers.IntegerField()

    class Meta:
        model = Book
        fields = ('id', 'title', 'authors')

views.py

class BookViewSet(viewsets.ModelViewSet):
    queryset = Book.objects.annotate(authors=Count('author'))
    serializer_class = BookSerializer
    ...

That will make the counting at database level, avoiding to hit database to retrieve authors count for each one of the returned Book items.

More Related Contents:

  1. Does the django-rest-framework provide an admin site to manage models?
  2. How can I enable CORS on Django REST Framework
  3. DRF: Simple foreign key assignment with nested serializers?
  4. Django Rest Framework File Upload
  5. How do I include related model fields using Django Rest Framework?
  6. Include intermediary (through model) in responses in Django Rest Framework
  7. Django REST Framework upload image: “The submitted data was not a file”
  8. Django REST Framework POST nested objects
  9. Django serializer Imagefield to get full URL
  10. Django Rest Framework and JSONField
  11. How can I use Django OAuth Toolkit with Python Social Auth?
  12. django.db.migrations.exceptions.InconsistentMigrationHistory
  13. Django Rest Framework writable nested serializers
  14. Pass extra arguments to Serializer Class in Django Rest Framework
  15. Django REST: Uploading and serializing multiple images
  16. When to use Serializer’s create() and ModelViewset’s perform_create()
  17. Django Rest Framework – Authentication credentials were not provided
  18. Logging requests to django-rest-framework
  19. Django REST Framework serializer field required=false
  20. Django Rest Framework – Could not resolve URL for hyperlinked relationship using view name “user-detail”
  21. Django Rest Framework – How to add custom field in ModelSerializer
  22. OperationalError, no such column. Django
  23. Django Python rest framework, No ‘Access-Control-Allow-Origin’ header is present on the requested resource in chrome, works in firefox
  24. Django viewset has not attribute ‘get_extra_actions’
  25. How to use csrf_token in Django RESTful API and React?
  26. Override JSONSerializer on django rest framework
  27. Django: app level variables
  28. How to add custom field in ModelSerializer?
  29. CSRF validation does not work on Django using HTTPS
  30. Multiple lookup_fields for django rest framework

Leave a Comment