Hibernate version:
3.x

So we have a base type and then a bunch of derived types. These are all types of content. We need to be able to do searches, but then we want to be able to group the results into subtype buckets. The base is called Post, the subtypes would be Discussion, Article, Blog, etc. Is there an elegant way to do this? Short of doing something like grouping on the discriminator column in the base class?

Thanks.

Can you clarify your problem a little. When you search 'search' do you mean Hibernate Search (Hibernate + Lucene) or plain HQL or JPA?

If you are talking about HQL then a group by on the discriminator column should work.

Yes the search is going to be a text search, e.g. look for the word salmon, and have it find mention in blogs, discussions, stories, etc. So the question is how to see results grouped properly by subtypes.

It depends what you want to achieve.
If you want to find the best matches globally and then split them by subtype, a split routine written in Java post Hibernate Search query is the right approach.
If you want to find the best matches for each category, then one query per category is probably best (ftem.createFTQuery(luceneQuery, Blog.class) ...)
Remember, Lucene queries are cheap.