>>
Do you think thats better? I don't really...
Anyway, we shouldn't take ODMG as a good model. The ODMG API is an API for OO
databases, not for OR mappers and so its somewhat badly adapted to the task at hand.
You can't do this:
database.lookup("name", Transaction.UPGRADE)
using the ODMG API. But for an OR tool that is the most efficient / natural way to do
things. So in fact, the proposed locking API is just as granular as ODMG, but also
more efficient in terms of database access.
<<
Not now, you brought to my attention a very good point that I had not considered. Note
that I am not experienced with OJB, just trying to learn the issues and the approaches.
>> A shared lock is acquired with an SQL "select...". <<
Actually the type of lock, lock duration, granularity and escalation depends on the
database and the isolation level. But I get your point.
>> There is really no cache-level locking. No thread *ever* blocks or recieves an
>> exception when trying to access the cache. The most that happens is that one
>> session gains exclusive access to the _cached_ representation of the object when it
>> tries to update it. Then all other sessions have to go to the database. If you
>> search back through this list, you'll see plenty of
previous discussions about how we maintain transaction isolation with this approach. <<
I spent several hours reading the treads today, searched on "transaction isolation"
and "lock isolation" (require all words) and the most helpful tread was "RE:
Pessimistic locking?"
(https://sourceforge.net/mailarchive/message.php?msg_id=1301809). I now understand
locking Session.lock() and loadWithLock() - used to support pessimistic locking ala
select for update. Thanks for your help.
Jeff Boring
Custom & Web Services Development
AT&T Labs
[EMAIL PROTECTED]
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