On Friday, April 17, 2020 at 8:02:50 PM UTC-4, Jens Troeger wrote:
>
>
> Indeed, Child does have multiple parents…
>
Ok, so this isn't a one-to-one relationship, but a many-to-many
relationship.
I would opt for a 3 table structure:
Parent
Parent_2_Child
Child
The AssociationProxy extension (part of SqlAlchemy itself) can
transparently map the Parent and Child relationships through the
Parent_2_Child table as attributes on Parent & Child tables itself. (
https://docs.sqlalchemy.org/en/13/orm/extensions/associationproxy.html)
The section "Simplifying Association Objects" (
https://docs.sqlalchemy.org/en/13/orm/extensions/associationproxy.html#simplifying-association-objects)
gives a good example of this on User/UserKeyword/Keyword
You could even remove the `oldest_child_id` and `youngest_child_id`
columns, and turn them into readonly attributes that can compute the child
as needed.
SqlAlchemy is very robust and you can do almost anything with it. I am
certain it is possible to build something that only uses the columns on the
Parent table to accomplish exactly what you desire... but it really sounds
like you should be using an association table in this model.
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