Transaction Isolation, was Re: SystemSpecifyer, was Re: [ZODB-Dev] How to predict George Bailey?

[Toby Dickenson]

On Monday 04 November 2002 2:24 pm, Christian Reis wrote:
> On Sun, Nov 03, 2002 at 07:36:33PM +0100, Magnus Lycka wrote:
> > Let's pretend this is a word processor. Should I drop and
> > reload my document every time I press Ctrl-S or Ctrl-Z?
>
> No, and this brings up a question for the ZODB wizards.
>
> With this discussion, I became aware of the issues that are related to
> having unrelated (in the domain sense) objects changing during a single
> transaction - meaning you have a transaction that changes an object her=
e
> but also there just because you happened to commit() on the second
> change.

Think about how this application would implement a correct Undo feature i=
f it=20
was not using ZODB.... Probably with an architecture that involves=20
application-level transaction awareness.

IMO the application architecture is broken if it doesnt include this, wit=
h or=20
without ZODB.

> And, more importantly, how can this be solved?=20

Keep the transactions out of your View, and avoid long-running transactio=
ns=20
altogether. I sketched out an architecture in M/V/C terms in this thread=20
yesterday.....