What methods have you used to improve query efficiency in Django?

To improve query efficiency in Django, I used the following methods:

• select_related() — for eager loading related objects through foreign keys, reducing the number of SQL queries.

• prefetch_related() — for preloading related objects, especially when working with many-to-many relationships.

• values() and values_list() — for selecting only the necessary fields, which reduces the amount of data transferred.

• annotate() and aggregate() — for performing calculations at the database level, reducing the load on Python.

• Using indexes — adding indexes on fields that are frequently filtered or sorted.

• Caching — applying caching of query results using Django's cache framework.

Example of using select_related():

# Without select_related: will result in N+1 queries
books = Book.objects.all()
for book in books:
    print(book.author.name)

# With select_related: one join query
books = Book.objects.select_related('author').all()
for book in books:
    print(book.author.name)