Django - Select Related & Prefetch Related ORM Optimization

Initial

Sales.objects.filter(sales_person=self)

Select Related (O2O)

Sales.objects.select_related().filter(sales_person=self)

Prefetch Related (M2M / M2O)

Sales.objects.select_related().prefetch_related('booking_set', 'advancepayment_set', 'others_set').filter(sales_person=self)

More info:
https://docs.djangoproject.com/en/dev/ref/models/querysets/#select-related
https://docs.djangoproject.com/en/dev/ref/models/querysets/#prefetch-related