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From Mahler Thomas <thomas.mah...@itellium.com>
Subject Prevayler based PB implementation
Date Mon, 15 Sep 2003 11:04:05 GMT
Hi all,

during the weekend I wrote a new PB implementation that is based on
prevayler (http://sourceforge.net/projects/prevayler/). It's already checked
in CVS.

Prevayler provides transparent and failsafe persistence for Java objects.
All Objects are kept in memory, only transaction logs and snapshots are
written to disk.
On restarting the application the latest snapshot + transactionlogs are
reexcuted to restore the latest memory state.

With Prevayler + OJB PB we now have a very simple OODBMS ! ODMG, OTM and JDO
can run on top of it as with the "normal" PB.

The implemementation is not yet complete, but it's already possible to
execute the PB tutorial application against it!

There are some still some todos:
- sequencemanagement. The Prevayler impl will need it's own SequenceManager,
as the SQL based version won't work.
- A query engine must be implemented. This is the largest todo. We need a
query engine, that is able to perform PB queries against the in-memory
database.
  Any ideas for this are welcome. This engine could be reused to provide
in-memory queries for ODMG and JDO.
- The In-memory Database must be improved to provide one Hashmap per class.

Unfortunately Prevayler is licenced under LGPL and we can not redistribute
it directly. 
As the prevayler concept is so simple I'm thinking of writing an ASF
licensed clean room implementation.
What do you think, is it worth the effort?

All ideas are welcome,

Thomas


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