Hi
(I apologize in advance if this is a silly question, but I'm having
some trouble figuring out why this isn't working as expected.)
I have 3 tables: Users, Xs, and Ys. Each has an id, and relevant data.
Each user can have a bunch of Xs as well as a bunch of Ys, for which I
have a ForeignKey("users.id") in Xs and Ys. In addition, each Y can
have 0 or more Xs. For this, I made an auxiliary table X_Ys containing
X and Y keys.
Tables:
usersTable = Table('users', metadata,
Column('id', Integer, primary_key=True),
...
)
ysTable = Table('ys', metadata,
Column('id', Integer, primary_key=True),
...
Column('user_id', Integer, ForeignKey('users.id'), nullable=False)
)
X_Ys = Table('x_ys', metadata,
Column('y_id', Integer, ForeignKey('ys.id'),
nullable=False, primary_key=True),
Column('x_id', Integer, ForeignKey('xs.id'),
nullable=False, primary_key=True))
XsTable = Table('xs', metadata,
Column('id', Integer, primary_key=True),
...
Column('user_id', Integer, ForeignKey('users.id'), nullable=False)
)
Mappers are:
mapper(User, usersTable, properties = {
'Ys': relation(Y, backref='user'),
'Xs': relation(X, backref='user'),
})
mapper(X, xsTable, properties = {
'Ys': relation(Y, secondary = X_Ys)
})
mapper(Y, ysTable, properties={
'Xs': relation(X, secondary = X_Ys)
})
then:
>>> u = User(...)
>>> u.Ys.append(Y(...))
>>> u.Ys[0].Xs.append(X(...))
>>> u.Ys
[<Y(...)>]
>>> u.Ys[0].Xs
[<X(...)>]
>>> u.Xs
[]
I was expecting/hoping that u.Xs would have the X that was appended to
u.Ys[0]. I can sort of make it work as long as I make the id columns
in X_Ys non-nullable. In that case, session.commit() throws an
IntegrityError if I don't manually set the user_id in any X objects to
a user id (Y objects get their user id ok). However, when I do that:
>>> u.Ys[0].Xs[0].user_id = u.id
>>> u.commit()
I seem to have to make a new session before the changes "show up" in
the user. ie. I must do:
sess.close()
sess = Session()
u = s.query(User).first()
before u.Xs has the element I'd expect. It does, however, seem to be
ok at that point.
Is there something dumb that I've set up wrong that someone could
point me at? Or is this just a "gotcha" to be avoided?
thanks,
scott
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