Django 4.2: advanced patterns with QuerySet Prefetching and Related Object Attributes
Quick question that's been bugging me - I'm currently working on a Django 4.2 application where I'm experiencing unexpected behavior when prefetching related objects in my QuerySet. I have a `Book` model that has a foreign key to an `Author` model and I'd like to fetch both books and their related authors efficiently. However, when I try to access author attributes after prefetching, they appear as `None` for some records. Here's the simplified code that I'm using: ```python from django.db import models from django.db.models import Prefetch 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) # Fetch books with prefetching books = Book.objects.prefetch_related('author').all() for book in books: print(f"{book.title} by {book.author.name}") ``` In some cases, I get the following behavior: ``` AttributeError: 'NoneType' object has no attribute 'name' ``` I have verified that all books have an associated author in the database. The scenario seems to occur when there are books for which the author was recently deleted, but I expected all related authors to be pre-fetched and not return `None`. Is there a way to handle this gracefully so that I can avoid exceptions when accessing related attributes? I've tried using `select_related` instead of `prefetch_related`, but it doesn't seem to work for this scenario due to the relationship type. Any help or insights would be greatly appreciated! I'm working on a CLI tool that needs to handle this. How would you solve this?