Django QuerySet Optimierung mit only() und defer() für Selektives Laden von Feldern

from django.db import models
 
class Article(models.Model):
    title = models.CharField(max_length=200)
    content = models.TextField()
    summary = models.TextField()
    author = models.ForeignKey('Author', on_delete=models.CASCADE)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    metadata = models.JSONField(default=dict)
 
# Fetch only required fields - reduces memory and query time
titles_and_dates = Article.objects.only('title', 'created_at').filter(
    author__name__icontains='python'
)
 
# Defer heavy fields that are rarely accessed immediately
articles_with_deferred_content = Article.objects.defer(
    'content', 'metadata'
).select_related('author').all()
 
# Combine with ordering and slicing
recent_titles = Article.objects.only(
    'title', 'created_at'
).order_by('-created_at')[:10]
 
# Chain with values() for dictionaries instead of model instances
author_names = Article.objects.values_list(
    'author__name', flat=True
).distinct()[:5]