Question

我在ndb模型中有一个类方法，我按“用户”（没有问题）和“行业”过滤。

问题是实体推荐没有行业属性，但有 stock 属性是Stock的KeyProperty，并且股票有行业属性

如何修复 get_last_n_recommendations_for_user_and_industry 方法按行业过滤，即Stock的KeyProperty？

class Industry(ndb.Model):
    name = ndb.StringProperty()
    ...

class Stock(ndb.Model):
    name = ndb.StringProperty()
    industry = ndb.KeyProperty(kind=Industry)
    ...

    @classmethod
    def get_industry(cls):
        return cls.query(cls.ticker == cls).get().industry

class Recommendation(ndb.Model):
    user = ndb.KeyProperty(kind=User)
    stock = ndb.KeyProperty(kind=Stock)
    ...

    @classmethod
    def get_last_n_recommendations_for_user_and_industry(cls, stock_key, user_key, n):
        return cls.query(
                cls.user == user_key, 
                cls.stock.get().industry == ndb.Key('Stock', stock_key.string_id()).get().industry
            )
            .fetch(page_size)

当我这样做时，我有这个错误：

AttributeError: 'KeyProperty' object has no attribute 'get'

Answer 1

您无法通过引用属性的属性进行过滤/查询，您需要在Recommendation模型中添加行业属性并对其进行查询。

class Recommendation(ndb.Model):
  user = ndb.KeyProperty(kind=User)
  stock = ndb.KeyProperty(kind=Stock)
  industry = ndb.ComputedProperty(lambda e:  
    Stock.industry.get_value_for_datastore(e.stock))

  @classmethod
  def get_last_n_recommendations_for_user_and_industry(cls, industry_key, user_key, n):
    return cls.query(
            cls.user == user_key, 
            cls.industry == ndb.Key('Stock', stock_key.string_id()).get().industry
        )
        .fetch(page_size)

NDB查询按KeyProperty过滤

1 个答案: