Hi at all,
I haven't found something by googling, but I'm also not sure about the
right search terms, so I hope some can help me here.
I have a model like this:
class Parent(DeclarativeBase):
id = Column(Integer, primary_key=True)
time = Column(Float)
another_id = Column(Integer)
class Child(DeclarativeBase):
id = Column(Integer, primary_key=True)
parent_id = Column(Integer, ForeignKey('parent.id'), nullable=False)
parent = relationship('Parent')
_time = Column(Float, nullable=True)
@property
def time(self):
return self._time or self.parent.time
So basically, a Child object may set it's own value for time, but if it's
not set, it uses the value from its parent.
This works, but I would also like to be able to do something like:
session.query(Child).filter(Child.parent.another_id==2)
(Which would throw Neither 'InstrumentedAttribute' object nor 'Comparator'
object has an attribute 'another_id')
And I wondered if this would be somewhat possible by using some of
sqlalchemy's fancy extensions! ;)
Thanks in advance,
Moritz
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