How do I optimize database queries in Django?

What are select_related and prefetch_related in Django?

select_related and prefetch_related are methods in Django ORM to optimize database queries. select_related uses SQL JOINs to fetch related objects in a single query, while prefetch_related performs separate queries and does the joining in Python.

When should I use select_related over prefetch_related?

Use select_related when you have a ForeignKey or OneToOne relationship and want to reduce the number of queries. Use prefetch_related for ManyToMany or reverse ForeignKey relationships, as it fetches related objects in a more efficient way.

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

Sure! For select_related, you can do something like MyModel.objects.select_related('related_model').all(). For prefetch_related, it would be MyModel.objects.prefetch_related('many_related_model').all().

What are the performance implications of using these methods?

Using these methods can significantly reduce the number of database queries, improving performance. However, be mindful of the amount of data being loaded, as fetching too much can lead to memory issues.