Re: [Hibernate-devel] database native keys

[Gavin_King/Cirrus%<CI...@ci...>]

> I was wondering how difficult it would be to support database native
> keys in hibernate (i.e. indentity columns in sybase/mssql), or if theres
> a reason why its not implemented atm in hibernate. If its really easy i
> could take a look at implementing it ;)

It would be great if you could get this going. It would certainly be a
great feature to have. I think the main difficulty would be this:

1. Hibernate always delays executing SQL statements until a flush(), so you
can't know what the generated key is until _after_ you execute the insert.
2. Hibernate uses the key in its internal data structures (and in other
ways) so its expecting to know the key _before_ you execute the insert.

Fixing this *should* be as simple as deciding to execute the insert
immediately for some classes (and sticking with the current behaviour for
others).

Have a look at:

(1) RelationalDatabaseSession.save(Object object, Serializable id)
(2) ClassPersister.insert(insert(Serializable id, Object[] fields,
SessionImplementor session)

These two methods do the work of
(1)
  * assigning an id,
  * calling PersistentLifecycle.create(),
  * copying the state of the object,
  * nullifying references to transient objects (in the copied state),
  * registering the object and its copied state in the sessions internal
data structure,
  * scheduling the actual insertion for later

(2)
  * actually executing the SQL insert

The class ScheduledInsertion adds an indirection between save() and insert
() that lets Hibernate execute the insertion "later". I suppose you would
want to remove this indirection....

Good Luck!