Instruction: Discuss the techniques available in Django to optimize ORM queries for performance.
Context: This question assesses the candidate's ability to write efficient database queries using Django ORM and their knowledge of optimization strategies.
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Firstly, select_related and prefetch_related are two powerful methods for reducing the number of database queries. select_related is used for foreign key and one-to-one relationships. It works by joining the related tables and fetching the necessary data in a single query. This is particularly useful when you know you will need related objects and want to avoid multiple queries.
prefetch_related, on the other hand, is designed for many-to-many and reverse foreign key relationships. It executes a separate lookup for each relationship and then does the "joining" in Python. This can significantly reduce query counts, especially when dealing with many objects that have multiple related items....