如何在 Django QuerySet 上执行“SELECT a or b < c FROM Table”？

Question

I have the following model:

class DiscountCoupon(models.Model):
   is_used = models.BooleanField(default=False)
   expiration_date = models.DateField()

   def is_available(self):
      if self.used or self.expiration_date <= date.today():
         return False
      return True

Instead of calling the is_available method iterating through a QuerySet, I want to do this operation into the QuerySet to perform better, like this:

SELECT (used OR (expiration_date < Now())) AS is_available FROM randomapp_discountcoupon;

Is this possible?

Answer 1

You can use Q objects as

from django.db.models import Q

discount_objects = DiscountCoupon.objects.filter(Q(is_used=True) | Q(expiration_date__lt=datetime.date.today())