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From Aristedes Maniatis <...@maniatis.org>
Subject Re: Why are most flattened relationships read-only?
Date Thu, 22 Mar 2012 21:37:18 GMT
On 23/03/12 2:40 AM, Schönfisch, Jörg wrote:
> Hi everybody,
>
> I'm trying to create a model which uses multiple levels of inheritance. Because of this,
I use many (flattened) 1:n-relationships between tables and subtables. Unfortunately, this
results in read-only relationships on deeper levels of the hierarchy.
> Is there any possibility to establish such a read-only relationship with Cayenne? Otherwise
the model is practically unusable as I have no existing data and solely want to create it
through the ORM.
> I wonder if there is any practical reason why flattened relationships are read-only?
Or is only the implementation to handle these lacking? Technically it should be possible to
make them writable, at least if the flattened relationship spans only foreign key constraints.


Since you have a special knowledge of your schema that Cayenne doesn't, perhaps you can write
your own helper methods which know how to create the intermediate tables and all their required
attributes. If the intermediate tables contain only foreign keys and nothing else, then Cayenne
could potentially do what you want. But that often isn't the case.


Ari



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Aristedes Maniatis
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