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?
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http://www.sqlalchemy.org/
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