Hi Jonathan,
The line you commented out from the example was either:
>
> children = relationship("Child")
>
> children = relationship("Child", back_populates="parent")
>
>
> both of those lines create an iterable list of all the Child objects on
> the `children`
>
Neither of them would work, because
sqlalchemy.exc.AmbiguousForeignKeysError: Could not determine join
condition between parent/child tables on relationship Parent.children -
there are multiple foreign key paths linking the tables. Specify the
'foreign_keys' argument, providing a list of those columns which should be
counted as containing a foreign key reference to the parent table.
Unfortunately, the following didn’t work either:
children = relationship("Child", foreign_keys=[oldest_child_id,
youngest_child_id])
(Oddly enough, specifying a list with a single element *does* work.)
Off the top of my head, the simplest way to accomplish this would be to add
> a "parent_id" column on the child table, and then create a relationship for
> "children" that correlates the `Parent.id` to `Child.parent_id`.
>
> That change might not work with your data model if a Child can have
> multiple parents.
>
Indeed, Child does have multiple parents…
--
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The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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