如何在新持久的 SQLAlchemy 2.0 模型上禁用延迟加载？

Question

我有一个接受 SQLAlchemy 模型实例的例程。它所做的一件事是查看子对象的数量。如果我通过 ORM 的 select() 函数加载模型并立即加载相关记录，则效果很好；但是，当我创建一个新对象时，保留它，然后将其传递给使用函数，因为我超出了会话范围，所以我收到一个 DetachedInstanceError 。如何禁用新持久实例上的行为？

示例代码：

class Base(DeclarativeBase):
    pass


class Customer(Base):

    __tablename__ = 'customers'

    customer_id: str = Column(String(36), primary_key=True)
    orders: Mapped['Order'] = relationship('Order', back_populates='customer')


class Order(Base):

    __tablename__ = 'orders'

    order_id: str = Column(String(36), primary_key=True)
    customer_id: str = Column(String(36), ForeignKey('customers.customer_id'))

    customer: Mapped['Customer'] = relationship('Customer', back_populates='orders')


customer = Customer()
print(customer.orders)  # Works fine

session.add(customer)

print(customer.orders)  # Uh-oh

Answer 1

禁用延迟加载：

orders: Mapped['Order'] = relationship('Order', back_populates='customer', lazy='noload')