Django query optimization with only and defer

                  from blog.models import Post


# Load only specific fields
posts = Post.objects.only('id', 'title', 'published_at')
for post in posts:
    print(post.title)  # No extra query
    # print(post.content)  # Would trigger extra query


# Exclude large fields
posts = Post.objects.defer('content', 'raw_content')
for post in posts:
    print(post.title)  # No extra query
    # Accessing content would trigger query


# Combine with select_related
posts = Post.objects.select_related('author').only(
    'id', 'title', 'author__username'
)


# For API responses
def get_post_list_data():
    return Post.objects.only(
        'id', 'title', 'slug', 'published_at', 'author_id'
    ).select_related('author').only(
        'author__id', 'author__username'
    )