[Tigerdb-team] Chages in tiger source

[<fre...@pa...>]

Hi,
I have commited some changes in the tiger source. The improvements are as
follows:
* Transaction isolation. All changes made by a thread are saved in a transaction
object and propagated to jdbm at commit. The changes are visible for that
thread but not for anyone else.

* Recovery handling. All changes made by a transaction are written to a temporary
transaction log before changes are propagated to jdbm. When all changes are
written to the transaction log and tiger is about to propagate the changes
to jdbm, the status (file extention) of the transaction log is changed from
temporary to redo. After the changes are propagated to jdbm the redo log
is deleted. If a system crash should occur before all changes are written
to the temporary log, no changes at all will be made. If a system crash occur
after all changes are written to the temporary log, all changes will be redone
next time tiger starts.

* Some class reorganizations. There are no longer a jdbm-specific broker
(JDBMPersistBrokerImpl). I have replaced it with the PersistBroker class.
I have defined a interface, ObjectStore, which may help us in the future
to replace jdbm with something else, if we want to.

I have just tested the changes with the very simple lasso application. But
I hope it will work as before.

/Fredrik



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