On Jun 8, 2011, at 5:19 PM, Eric Ongerth wrote:
> # Meanwhile, the following way of doing it doesn't work.
> # But it seems like it would make sense and might be worth enabling.
>
> class SomeClass(Base):
>
> __table__ = Table('sometable', Base.metadata,
> Column('id', Integer, primary_key=True),
> Column('discriminator', Text),
> Column('data', Text))
>
> __mapper_args__ = {'polymorphic_on': 'discriminator',
> 'polymorphic_identity': 'default'}
>
>
"polymorphic_on" someday might be able to handle more than just a column, and
there's no dependency-oriented rationale for allowing the string there like
there is with relationship(), so its better that it only accept the column for
now, which you can do easily enough via
{"polymorphic_on":__table__.c.discriminator} above.
> error it causes is not very clear. The error would be fine if it
> quoted the piece of code which triggered it, for instance if it said:
> * AttributeError: 'str' object 'discriminator' has no attribute
> 'proxy_set'.
we have a canned "columns only" function used by relationship() to check its
arguments, while there are probably a lot more places such a checker could go,
its additionally affixed to polymorphic_on in r760197daa0c2.
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