Looking at the "Common Problems" section I see this:

My problem is that I have a legacy database that's populated with data. I'm tryingb to migrate some nasty C++ code to Java with Hibernate. The structure looks something like this:

Class FOO {
int fooId
String fooName
Set<BAR> bar
}

Class BAR {
int fooId
int non_unique_value
}

I've created a primary key (fooId, non_unique_value) and by using a composite-id I can load the data. However I can't save back- I get "SQL insert, update or delete failed (row not found)."

Not clear what my options are here. I suppose I could add another column to the table, but I'm not sure howthat would affect the legacy code, or how I'd populate it with unique values - I'm not a DBA. Any help would be appreciated.

Well thanks for nothing, board. I eventually figured out a solution, which was to take a copy of the FOO:bar set and null out the original. That way I could save FOO. I could then iterate through FOO:bar and save each element in turn.

Seems a long-winded way to do it, but it works.