What is the difference between annotate and aggregate in Django?

What is the difference between annotate and aggregate in Django?

In Django, annotate is used to add a new field to each object in a queryset, while aggregate computes a single value from the entire queryset.

Can you give me an example of how to use annotate?

Sure! If you have a Book model and want to count the number of reviews for each book, you can use:

from django.db.models import Count
Book.objects.annotate(num_reviews=Count('reviews'))

And how would I use aggregate?

To get the average rating of all books, you can use:

from django.db.models import Avg
Book.objects.aggregate(Avg('rating'))

Are there any performance considerations I should be aware of?

Yes, annotate can lead to more complex queries and potentially slower performance if used on large datasets. aggregate is generally more efficient for summary calculations.