On Fri, Oct 27, 2017 at 4:57 PM, <char...@konversion.ca> wrote:
> My SQLAlchemy version is 1.1.14.
>
> I'm having difficulty understanding behaviours around a polymorphic
> hierarchy.
>
> I have an AbstractConcreteBase and two subclasses.
>
> The ACB declares some attributes shared by the two subclasses, and the
> subclasses have attributes of their own that are not shared(i.e. they are
> not part of the shared identity represented by the ACB).
>
> class MyBase(AbstractConcreteBase, Base, Mixin):
> shared_id = Column(Integer, default=Sequence("database_shared_id_seq",
> start=0, increment=1), primary_key=True)
>
> @declared_attr
> def name(self):
> return Column(String(100), nullable=False)
>
> @declared_attr
> def foreign_key(self):
> return Column(Integer, ForeignKey("MyOtherTable.id"))
>
> ...
>
>
> class Concrete1(MyBase):
> start = Column(Date)
> end = Column(Date)
>
>
> class Concrete2(MyBase):
>
> @property
> def start(self):
> return self.details.start
>
> @property
> def end(self):
> return self.details.end
>
> details = relationship("Concrete2Detail", uselist=False, viewonly=True)
>
>
> As you can see, "start" and "end" are not declared in the ACB and are
> implemented differently between the table. I don't want them to be shared by
> the subclasses.
>
> When I query one of the Concretes, the ACB mapper is updated with the
> "start" and "end" attributes, and then the Concretes are expected to
> implement the attributes on the mapper level(which is not the case for
> Concrete2).
>
> How can I prevent this from happening?
>
Can you provide a full script that demonstrates the problem?
Thanks,
Simon
--
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http://www.sqlalchemy.org/
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