Hi! Got this setup:
class Document(Base):
__tablename__ = 'document'
discriminator = Column('type', String(30))
__mapper_args__ = {'polymorphic_identity':'document',
'polymorphic_on': discriminator}
id = Column(Integer, primary_key=True)
number = String(20)
class Invoice(Document):
__tablename__ = 'invoice'
__mapper_args__ = {'polymorphic_identity':'invoice'}
id = Column(Integer, ForeignKey('document.id'), primary_key=True)
customer = String(100)
linked_document_id = Column(Integer, ForeignKey('document.id'))
And, predictably, I get "sqlalchemy.exc.AmbiguousForeignKeysError: Can't
determine join between 'document' and 'invoice'; tables have more than one
foreign key constraint relationship between them. Please specify the
'onclause' of this join explicitly." As I understand, augmenting Invoice's
__mapper_args__ with 'inherit_condition ': (id == Document.id) will deal
with the problem. However, in my case I cannot call (id == Document.id),
because it all is going on inside a metaclass I've devised for reasons
beyond this topic and the class being created (Invoice) does not yet exist
at the time of setting __mapper_args__ , so accessing this ID class member
is problematic. So the question is this: can I set 'inherit_condition' by
using some other way, like string form or something? Thanks!
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