👀 Views: 0 💬 Answers: 1 📅 Created: 2025-08-23

django performance queryset Python

I'm working on a project and hit a roadblock... This might be a silly question, but I've been banging my head against this for hours. I'm working with a important performance scenario when querying a large dataset in Django. I have a model `Author` that has a foreign key relationship with a model `Book`, and I want to fetch all books along with their associated authors efficiently. Using `prefetch_related`, I expect the database queries to be optimized, but I notice that the query still takes a long time to complete. Here's the relevant section of my code: ```python from django.db import models class Author(models.Model): name = models.CharField(max_length=100) class Book(models.Model): title = models.CharField(max_length=200) author = models.ForeignKey(Author, related_name='books', on_delete=models.CASCADE) # Attempting to fetch books with prefetch_related books = Book.objects.prefetch_related('author').all() for book in books: print(f'{book.title} by {book.author.name}') ``` Despite using `prefetch_related`, I found that the query still results in multiple queries being executed when I know the dataset should allow for optimization. The following message shows up in my logs: ``` WARNING: QuerySet contains more than 1000 items, consider using pagination. ``` I’ve tried running `django-debug-toolbar` to analyze the queries being executed, and it shows that while it does make fewer queries than without `prefetch_related`, the total time for fetching data remains high. I also tried using `select_related` on the foreign key, but since the relationship is one-to-many (one author can have many books), I ran into issues with data duplication in the resulting query. The dataset I’m working with contains over 50,000 book entries, and I’m running Django version 3.2. I need to understand if the scenario lies in the way I’m querying the data or if there are other optimizations I can apply to improve performance. Any suggestions would be greatly appreciated! Any help would be greatly appreciated! This is part of a larger service I'm building. What am I doing wrong?