I am using Seam in a very important project of my company. In my project I need a base entity class and it has more than ten sub entity classes. I don't want to use single table strategy because the number of fields of the sub entities vary widely. But if I use the joined subclass strategy, a query for the base entity will always be polymorphic and will join all the sub entity table. This is very inefficient apparently. Is it possible to avoid this problem?
I'm not sure if this is what you are asking for. Take a look at the following post http://www.jboss.com/index.html?module=bb&op=viewtopic&t=83732. It might handle what you are looking for, but in a persistent way instead of querying.
With kind regards