Prefetching related objects in Django allows you to retrieve related objects for a queryset or a list of model instances at once, instead of making one query for each related object. This can improve performance, especially when dealing with large datasets.
To use prefetch with related_name relation in Group by, follow these steps:
class Author(models.Model):
name = models.CharField(max_length=100)
class Book(models.Model):
title = models.CharField(max_length=100)
author = models.ForeignKey(Author, on_delete=models.CASCADE, related_name='books')
authors = Author.objects.prefetch_related('books').all()
from django.db.models import Count
authors_by_name = Author.objects.annotate(num_books=Count('books')).order_by('-num_books')
authors_by_name = authors_by_name.values('id', 'name', 'num_books')
from rest_framework import serializers
class BookSerializer(serializers.ModelSerializer):
class Meta:
model = Book
fields = ('id', 'title')
class AuthorSerializer(serializers.ModelSerializer):
num_books = serializers.IntegerField()
books = BookSerializer(many=True)
class Meta:
model = Author
fields = ('id', 'name', 'num_books', 'books')
serializer = AuthorSerializer(authors_by_name, many=True)
This will give you a serialized queryset of authors sorted by the number of books they have, along with a list of their books. The related books will be pre-fetched using the 'books' related_name.
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Asked: 2023-06-20 07:50:53 +0000
Seen: 8 times
Last updated: Jun 20 '23
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