[Zope] More on understanding conflicts

[Chris McDonough]

On Dec 21, 2005, at 12:40 PM, Dennis Allison wrote:

>
> Chris W,
>
> The issue here has had to do with session variables and their  
> iteraction
> with the persistence mechanism and conflicts and multiple threads  
> for the
> same session.  Chris McDonough has pointed out that session  
> variables can
> cause writes and write conflicts even if the only Zope level access  
> is a
> read.  I thought MVCC works out of the box for Zope 2.8.4 which  
> uses ZODB
> 2.3.4. Am I wrong?

It does.  But MVCC does not prevent write conflicts.  Only read  
conflicts.

>
> The real surprise was that you can get a write conflict from a pair of
> session variable reads!

That is surprising, no doubt. ;-)