所以,我有一个类似的模型:
class Foo(model):
__tablename__ = "foo"
id = Column(Integer, primary_key=True)
data = relationship(
"FooData",
cascade="all, delete-orphan",
backref="foo",
lazy="dynamic",
order_by="desc(FooData.timestamp)"
)
@property
def first_item(self):
# the problem is here:
return self.data.order_by(asc("timestamp")).first()
@property
def latest_item(self):
return self.data.first()
class FooData(Model):
__tablename__ = "foo_data"
foo_id = Column(Integer, ForeignKey("foo.id"), primary_key=True)
timestamp = Column(DateTime, primary_key=True)
actual_data = Column(Float, nullable=False)
所以,问题在于first_item
那里的方法:当它按照上面的方式定义时,SQL看起来像这样:
SELECT foo_data.timestamp AS foo_data_timestamp, foo_data.actual_data AS foo_data_actual_data, foo_data.foo_id AS foo_data_foo_id
FROM foo_data
WHERE :param_1 = foo_data.foo_id ORDER BY foo_data.timestamp DESC, foo_data.timestamp ASC
-- ^^^^^^^^^^^^^^^^^^^^^^
显然,order_by
查询中指定的内容将附加到关系定义中指定的内容,而不是替换它;有没有办法让查询覆盖原来的order_by
?我知道我可以直接在FooData
类,但如果可能的话我想避免这种情况。