Thanks Mike. This is good to know.
On Tuesday, January 7, 2020 at 5:53:19 PM UTC-8, Mike Bayer wrote:
>
> to accomplish this you would need to rewrite the
> orm.util.polymorphic_union function to include these additional expressions
> within each SELECT under a common label name, then override the part of
> AbstractConcreteBase which applies the polymorphic_union in order to
> accomplish this.
>
> These two functions could be enhanced to support additional expressions
> added to the polymorphic_union however that's not available right now.
>
> Otherwise, you need to select from TableA and TableB explicitly and write
> the UNION directly.
>
> if this in fact a "toy" example then I would say you're better off not
> using concrete inheritance as it is not very fluent.
>
>
>
>
> On Tue, Jan 7, 2020, at 1:38 PM, Damian Yurzola wrote:
>
> Folks I have this toy example I've sanitized.
>
> class TableBase(AbstractConcreteBase, Base):
> pass
>
>
> class TableA(TableBase):
> __tablename__ = "table_a"
> __mapper_args__ = {
> "polymorphic_identity": "A",
> "concrete": True,
> }
>
> v0 = Column(Integer)
>
> @hybrid_property
> def magic(self):
> return self.v0 * 100
>
> @magic.expression
> def magic(cls):
> return cls.v0 * 100
>
>
> class TableB(TableBase):
> __tablename__ = "table_b"
> __mapper_args__ = {
> "polymorphic_identity": "B",
> "concrete": True,
> }
> v0 = Column(Integer)
>
> @hybrid_property
> def magic(self):
> return self.v0 * 10
>
> @magic.expression
> def magic(cls):
> return cls.v0 * 10
>
>
> When I query at the top level:
>
> print(Query([TableBase.magic]).limit(1).statement)
>
> I get
>
> AttributeError: type object 'TableBase' has no attribute 'magic'
>
>
> I've tried a bunch of things, most of them point to the fact that the
> hybrid_property is not being rendered in the subquery.
> I did solve it by moving the hybrid_property into the abstract class,
> though I want the particularities of a table to stay with the table
> definition and not at the union level.
>
> Thoughts? Ideas?
>
> Thanks!!!
>
> --Damian
>
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
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SQLAlchemy -
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http://www.sqlalchemy.org/
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