On Sep 21, 2010, at 8:42 PM, Michael Hipp wrote:
>
> class Car(Base):
> __tablename__ = 'cars'
> id_ = Column(Integer, primary_key=True)
> auct_id = Column(Integer, ForeignKey('auctions.id_'), nullable=False)
> auction = relationship('Auction', backref=backref('cars', order_by=lane))
>
> If I do this, it fails trying to do an 'INSERT' on the new Car.
> new.auction = old.auction
>
> If I change that to:
> new.auct_id = old.auct_id
>
> It attempts an UPDATE as expected. (I don't understand why that
> auct_id/auction column would have that effect; it's not a primary key.)
It definitely does not attempt an INSERT if id_ is set to a non-None value,
assuming that row already exists in the DB, without something else in your
model/usage causing that to happen. If id_ is None or the given id_ doesn't
exist in the DB, you get an INSERT. auct_id has no direct effect here.
>
> But that won't work because new.auction is still None so when I attempt a
> commit it fails with:
>
> Exception: IntegrityError: (IntegrityError) null value in column "auct_id"
> violates not-null constraint
> 'UPDATE cars SET make=%(make)s, auct_id=%(auct_id)s,
> version_id=%(version_id)s WHERE cars.id_ = %(cars_id_)s AND cars.version_id =
> %(cars_version_id)s' {'auct_id': None, 'make': '', 'cars_version_id': 1,
> 'cars_id_': 2, 'version_id': 2}
that also makes no sense since if you set "auct_id" manually, assuming
old.auct_id is not None, it wouldn't be None in the UPDATE statement.
>
> Why is 'auction' causing it to do an INSERT and how can I set it?
No idea. There's definitely more going on that you aren't illustrating here.
As usual, distilling down the behavior that appears wrong into a single
file/no-dependencies/test-data-provided-inline/fully runnable/reproducible test
will reveal either the issue in your usage, or whatever bug/subtle SQLAlchemy
issue is at play.
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