[Hibernate] Are toplevel collections / subcollections a Bad Thing?

[Gavin K. <Gav...@ex...>]

I'm (again) considering deprecating toplevel collections and
subcollections=20
in Hibernate 2.0. I was never completely happy with this feature after I

implemented it, but it had taken so much effort to get it to work that I
left it in.

The case against toplevel collections is:
* the relational model is broken - there is no foreign key constraint
from=20
collection element row to the owning row
* subcollections complicate code in SessionImpl _significantly_

The case for keeping them is:
* they let you persist a Java "collection of collections"
* they let you have a single table / collection mapping that can be used
by=20
different owning classes
* instances of a toplevel collection can be passed between different
owners=20
(even between owners of a different class, potentially) without needing
to=20
remove and recreate the collection rows
* they currently work and I havn't needed to touch the complicated code
for=20
a long time now

So: Do people USE this feature?? Have people really actually found uses=20
for this stuff, or is it actually just making Hibernate harder to
understand=20
for the first time? Even if it has been useful, is perhaps *still*
undesirable,=20
because of concerns about data integrity? Perhaps we simply shouldn't=20
be encouraging this kind of relational model.....

I need advice on this.

Gavin


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