[ZODB-Dev] Multi-version concurrency control

[Tino Wildenhain]

Hi,

Jeremy Hylton wrote:
> On Mon, 2003-09-29 at 10:11, Casey Duncan wrote:
> 
>>>http://www.zope.org/Wikis/ZODB/MultiVersionConcurrencyControl
>>
>>This is very well written, not an easy thing to explain to the proletariat 
>>down here ;^)
> 
> 
> Thanks :-).
> 
> 
>>A question: Will the ZODB provide a way to revert to the current behavior when 
>>the application wishes to retrieve the latest revision of an object 
>>regardless of the state of that object at the start of the transaction? I can 
>>think of a couple places where this would be desireable.
>>
>>I suspect the answer is to call load() explicitly in a particular way that 
>>means "current revision", no?
> 
> 
> load() will always mean current revision.  I think the way to deal with
> this is to add an option to a connection.  You can either get MVCC or
> you can always get the current object and risk conflict errors.
> 
> Jeremy

Why not borrow behavior from current MVCC databases like Postgresql?
There are several transaction modes (read: isolation levels) available
(SERIELIZEABLE, READ COMMITED) you can set mid stream but before
any object access.
(e.g. always at the start of a transaction)

Regards
Tino