django - Django 查询在模型字段之间进行简单的算术运算并与来自另一个模型的字段进行比较

Question

（下面的所有代码都是实际代码的简化表示）。

如果我有以下 Django 模型：-

class Material(models.Model):
    name = models.CharField(max_length=110)

class OrderDetail(models.Model):
    material = models.ForeignKey(Material)
    order_quantity = models.IntegerField()
    quantity_delivered = models.IntegerField(null=True, blank=True)
    is_open = models.BooleanField()
    is_active = models.BooleanField()

class MaterialRequirement(models.Model):
    material = models.ForeignKey(Material)
    quantity = models.IntegerField()

我有一个MaterialRequirement模型实例，我们称之为material_requirement。我正在尝试检索OrderDetail满足以下条件的对象：-

1. material = material_requirement.material

2. is_open = True

3. is_active = True

4. order_quantity > quantity_delivered

5. material_requirement.quantity <= order_quantity - quantity_delivered

我的问题是如何在下面的 ORM 查询中合并第 5 个选择标准。

order_details = OrderDetail.objects.select_related('material').filter(material=material_requirement.material,
                                                                    is_open=True,
                                                                    is_active=True,
                                                                    order_quantity__gt=F('quantity_delivered'))

Answer 1

order_details = (OrderDetail.objects.select_related('material')
                 .filter(material=material_requirement.material,
                         is_open=True,
                         is_active=True,
                         order_quantity__gt=F('quantity_delivered'),
                         quantity_delivered__gte=F('order_quantity') - material_requirement.quantity,
                         )
)

Answer 2

order_details = order_detail.extra(where=["order_quantity - quantity_delivered <= %d" % material_requirement.quantity]))