Hi,
I've got a problem understanding how to handle relationships with
polymorphism
Sorry for the db design (I took it overs as it is ).
I've got a parent class Task
class Task(DBBASE):
__tablename__ = 'task'
id = Column(Integer, primary_key=True)
amount = Column(Integer)
and two child classes
class Invoice(DBBASE):
__tablename__ = 'invoice'
id = Column(Integer, ForeignKey('task.id'), primary_key=True)
date = Column(Date)
project_id = Column(Integer, ForeignKey('project.id'))
project = relationship("Project", backref=backref('invoices',
order_by='Invoice.date'))
specific_attr1 = Column(Integer)
class Esimation(DBBASE):
__tablename__ = 'estimation'
id = Column(Integer, ForeignKey('task.id'), primary_key=True)
date = Column(Date)
project_id = Column(Integer, ForeignKey('project.id'))
project = relationship("Project", backref=backref('estimations',
order_by='Invoice.date'))
specific_attr2 = Column(Integer)
specific_attr3 = Column(Integer)
I'd like to query something like:
dbession.query(Task).with_polymorphic([Invoice,
Estimation]).join(Invoice.project).join(Estimation.project).join(Project.client)
I actually get an error :
(1066, "Not unique table/alias: 'project' ")
1- I've tried to add a aliased=True to the with_polymorphic call, but it
gives me "<lambda>() got an unexpected keyword argument 'aliased'"
2- I've tried to build two queries and use union_all but then I need to
specify all the columns and there are something like 40 columns to query.
How should I do to build this query ?
Cheers,
Gaston
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