I'm not able to reproduce the issue you describe. Below is an MCVE, can you
please modify it to show the failure you are getting? The .foo attribute on B
is returned:
from sqlalchemy import Column
from sqlalchemy import create_engine
from sqlalchemy import Integer
from sqlalchemy import String
from sqlalchemy.ext.declarative import AbstractConcreteBase
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.declarative import declared_attr
from sqlalchemy.orm import configure_mappers
from sqlalchemy.orm import query_expression
from sqlalchemy.orm import Session
from sqlalchemy.orm import with_expression
Base = declarative_base()
class A(AbstractConcreteBase, Base):
@declared_attr
def foo(cls):
return query_expression()
class B(A):
__tablename__ = "b"
id = Column(Integer, primary_key=True)
data = Column(String(50))
__mapper_args__ = {"polymorphic_identity": "b"}
class C(A):
__tablename__ = "c"
id = Column(Integer, primary_key=True)
__mapper_args__ = {"polymorphic_identity": "c"}
configure_mappers()
e = create_engine("sqlite://", echo=True)
Base.metadata.create_all(e)
session = Session(e)
session.add(B(id=1, data='b data'))
session.commit()
b1 = session.query(A).options(with_expression(A.foo, B.data + ' hi')).all()[0]
assert b1.foo == "b data hi"
On Wed, Mar 25, 2020, at 12:30 PM, Benjamin Beguin wrote:
> Hi there,
>
> I'm facing an issue with the use of AbstractConcreteBase class and a
> @declarred_attr returning a query_expression()
>
>
> class A(AbstractConcreteBase, Base):
> @declared_attr
> def foo(cls):
> return query_expression()
>
>
> class B(A):
> ...
>
>
> class C(A):
> ...
>
>
> objects = db.session.query(A).options(with_expression(A.foo,
> my_expression)).all()
>
>
>
> B and C objects returned have the property foo but it is None
> The generated SQL query returns a value for the expression but the mapping
> seems to be not effective
>
> Am I doing something wrong ?
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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