What is the best way to store inherited domain objects? For example, I have a Business object, but there are actually 4 types of businesses. Most of them actually have only 1 field, but one of them has a few extra fields. I figured I could have 5 tables all together, but I'm not really sure how to approach it exactly.

I know hibernate supports subclasses, but I was wondering what are the performance trade offs for using this feature?

Also, if I had 5 tables, how would I figure out what type the business is? I figured I could just join the business table with all the other business type tables, but that would be low performance, would it not?

Thanks so much.

I'm using postgres's inheritance by the way.

Well, it doesn't appear that hibernate has direct support for postgres inheritance. I guess I just have to make 4 seperate mappings, although I don't like that idea since that's duplication, making the mapping file hard to maintain (potentially if a common field is added/edited/removed).

Well, time for sleep. I'll look back tomorrow I guess.

well, I couldn't sleep. heh.

I ended up just making seperate tables without the postgres specific way of doing inheritance and did joined-subclass and worked without a problem first crack. I guess this is better anyway since there is no duplication now.

PLEASE BE PATIENT!

have you read the doc?

Of course. It's not that I couldn't get either of them to work, it's just that I didn't know which to use with postgres's internal inheritance. I think the answer is simply none, so I just implemented the join-subclass way of doing it and got rid of those inherited tables and just made simple tables that all referenced the business table as their primary key (which worked without a hitch).

I just wanted to know what the best strategy was to avoid mapping duplication while having the benefits of using postgres's table inheritance, but since it appears that hibernate doesn't know they are inherited because postgres gives the illusion that they are not, there isn't much way for hibernate to know so I would have to duplicated 4 mappings with minor differences.

i believe there are two polymorphic devices in hibernate that will support batching (and, hence, greater performance for mass updates):

1. subclass and superclass share the same table. use a key column to indicate the subclass type. table must contain an aggregate of all columns required by all subclasses.

2. use encapsulation and model "subclasses" as separate objects. do not use the subclass feature in hibernate. do not use cascading updates or inserts.

Gavin, please correct me if i am wrong.

Um, that sounds right, I guess...