Re: [Gnumed-devel] re: non-serializability detection

[Karsten Hilbert]

> This is about gmPG, gmBusinessObject.
> when a medical record is opened, are long running transactions kept open ?
No. Unlocked transactions aren't of particularly great value.
Locked transactions are to be avoided.

> Otherwise, in a commit of an update on an old value, would checking
> a timestamp or sequence number be needed ?
Yes.

> dbobjects seem to be checked out in one transaction, held for some time, 
> and then checked-in in another transaction
Correct.

> and serializability is only an issue if someone else is
> checking out or checking in during the short time of the
> checking-in transaction.
Yes.

> But actually, the transaction should run from when the
> dbobject is checked out to when it's checked in if the in-built
> sql transaction mechanism is to be used for serializability
> enforcement, and preventing lost updates.
Correct.

> So application transaction checks might be needed, either application 
> locks or timestamps
> held , checked and updated at the server when dbobjects are created or 
> completed, in order to
> abort or warn against a lost update.
Correct.

Our solution to this is all the fiddling with XMIN. The full
explanation is in the archives linked from the Wiki.

Karsten
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