Optimizing Django Queries with Prefetch Related for Nested Relationships
Could someone explain Recently started working with a Django application where I'm tasked with optimizing database queries that involve nested relationships. The models are set up such that a `Book` can have multiple `Authors`, and each `Author` can have multiple `Awards`. Fetching all books along with their authors and awards can be quite slow, especially with larger datasets. I've tried using `select_related` to fetch related `Authors`, but it doesn’t cascade to get the `Awards`. Here's a simplified version of what I attempted: ```python books = Book.objects.select_related('author').all() for book in books: print(book.title, book.author.name) ``` This only retrieves authors and not their awards, which leads to additional queries when I access the awards. To solve this, I looked into `prefetch_related`. Here's what I implemented: ```python from django.db.models import Prefetch awards = Award.objects.all() books = Book.objects.prefetch_related(Prefetch('author_set', queryset=Author.objects.prefetch_related('awards'))) ``` While this approach seems better, I still notice performance issues when there are many authors and awards per book. Should I consider creating a custom query or perhaps use raw SQL for this? Also, is there a recommended way to evaluate the performance of these queries? Any insights on how to best approach this would be greatly appreciated. Any ideas what could be causing this?