I'm having trouble with many-to-one relationships to subclasses that use
single table inheritance. I have tried this in 0.5.8 and 0.6beta1.
Here is my test case:
import sqlalchemy as sa
from sqlalchemy import orm
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
employee = sa.Table("employee", Base.metadata,
sa.Column("id", sa.Integer, primary_key=True),
sa.Column("type", sa.Integer, nullable=False))
class Employee(Base):
__table__ = employee
__mapper_args__ = {"polymorphic_identity": 0,
"polymorphic_on": employee.c.type}
class Engineer(Employee):
__mapper_args__ = {"polymorphic_identity": 1}
class Other(Base):
__tablename__ = "other"
# Fields
id = sa.Column(sa.Integer, primary_key=True)
engineer_id = sa.Column(sa.Integer,
sa.ForeignKey("employee.id"))
# Relations
engineer = orm.relation("Engineer")
print Other.engineer.has()
I get this exception:
AttributeError: 'ClauseList' object has no attribute 'proxy_set'
This appears to be the same issue described at
http://groups.google.com/group/sqlalchemy/browse_thread/thread/7fcb0c0c6e1c809f.
Is this a bug? Currently, I am working around the issue by changing
Other.engineer to refer to Employee and using
Other.engineer.of_type(Engineer).has(), but this is less than ideal.
NOTE: In my real use case, I have compound foreign keys and check
constraints on Other to ensure that its engineer_id only points to
Engineer objects. However that was not necessary to demonstrate the
problem, so it has been omitted here.
Thanks,
-Conor
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