[ZODB-Dev] Re: MVCC and packing

[Toby Dickenson]

On Thursday 09 October 2003 12:22, Jeremy Hylton wrote:
> On Thu, 2003-10-09 at 05:19, Toby Dickenson wrote:
> > Ive been thinking about the interaction of MVCC and packing.... The
> > natural implementation in most storages could lead to incorrect behaviour
> > if loadNonCurrent was asked about a transaction that predates the most
> > recent pack.
>
> I think that's right.  Did I forget to mention this in the plan?
>
> > Is it the responsibility of the storage to check this?
>
> Yes.  If the transaction specified in loadNonCurrent() has been packed,
> then the storage should not return data.  I'm not sure if it should
> return None or raise an exception.

The storage will raise some kind of KeyError for ancient objects that have 
been entirely removed by packing. I would also expect some kind of KeyError 
for revisions that are only slightly too old.

-- 
Toby Dickenson