python - Flask 管理员 - 对 hybrid_property 进行复杂排序

Question

我有一个相当复杂的 hybrid_property。这是一个供应商模型，它有多个 skuchannels(产品)。它的作用是:根据 target_stock_duration(例如，我们希望将商品存货 4 个月)计算必须订购的单位数量以及这将花费多少。这给了我们潜力。

class Vendor(db.Model):
    __tablename__ = "vendor"
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(150))
    b2c_price_factor = db.Column(db.Float, nullable=False)
    skuchannels = db.relationship("SKUChannel", back_populates="vendor")

    @hybrid_property
    def po_potential(self):
        """This is a "virtual" property that will that can be used in the admin view. It calculates
        the potential value for a comming PO.

        Returns:
            _type_: _description_
        """
        
        potential = 0
        for item in self.skuchannels:
            purchasing_price = item.purchasing_price if item.purchasing_price != None else 0
            
            target_stock_duration = 4

            try:
                to_order = item.average_monthly_sales * target_stock_duration - item.stock_level #calculate how many units we have to order
                if to_order < 0:
                    to_order = 0
            except TypeError:
                to_order = 0
            
            potential = potential + purchasing_price * to_order #calculate how much everything costs

        return potential

好吧，这个 hybrid_property 工作得很好，但我非常想对这个属性进行排序。使用@po_potential.expression -> 好吧，我不知道该怎么做，因为据我所知，它应该返回一个选择对象。还有其他办法吗？

Answer 1

这应该让你开始:

class Vendor(Base):
    ...
    ...
    @po_potential.expression
    def po_potential(cls):
        target_stock_duration = 4
        return (
            select(func.sum(
                func.ISNULL(SKUChannel.purchasing_price, 0) *
                func.GREATEST(0, SKUChannel.average_monthly_sales * target_stock_duration - SKUChannel.stock_level, 0)
            ))
            .where(SKUChannel.vendor_id == cls.id)
            .label('po_potential')
        )