[hibernate-dev] JPA2 locking followup...
smarlow at redhat.com
Thu Nov 12 08:56:51 EST 2009
More JPA-2 locking support is checked in for HHH-4546. As per Steve's
suggestion, we can now customize dialects to control how core locking
(optimistic +pessimistic) is performed against different database servers.
We now have the following additional Hibernate LockModes that are used
for JPA-2 locking:
OPTIMISTIC - Verify that version hasn't changed just prior to
OPTIMISTIC_FORCE_INCREMENT - Verify that version hasn't changed and
increment version. Performed just prior to transaction commit.
PESSIMISTIC_READ - Immediately obtain a read (or greater) entity
PESSIMISTIC_WRITE - Immediately obtain a write entity database lock.
PESSIMISTIC_FORCE_INCREMENT - Immediately obtain a write entity database
lock and increment the version.
I propose that we make the following database dialect changes for the above:
1. For Oracle, I believe that "select for update" is now getting a
shared database lock. I propose that we tailor the Oracle dialect to do
a "select for update" for LockMode.PESSIMISTIC_READ. The Oracle dialect
should also handle LockMode.PESSIMISTIC_WRITE by using the above
described behavior for LockMode.PESSIMISTIC_FORCE_INCREMENT (JPA-2 spec
2. For SQL Server dialect, we could use "holdlock, rowlock" for
LockMode.PESSIMISTIC_READ and "updlock, rowlock" for
LockMode.PESSIMISTIC_WRITE. There are probably other variations to
consider (e.g. Snapshot Isolation mode).
Perhaps we will get some community help in customizing the dialects. :-)
On 11/06/2009 09:04 AM, Scott Marlow wrote:
> Initial support for locking is checked in via HHH-4546.
More information about the hibernate-dev