[ZODB-Dev] Supporting a DataManager without Two Phase Commit

[Andreas Jung]

--On 5. Mai 2007 02:46:58 +0200 Andreas Jung <lists at zopyx.com> wrote:

>
> If commit fails or another DataManager fails, data is not commited to the
> database.
>

However I am not sure if this is completely true. Although this approach 
ensures that all SQL statements were execute properly it does not take into 
account that a commit operation itself might fail even at that point for 
some reason. Even the Python DB API itself does not support the TPC and 
most don't driver don't support TPC through an API. So that's basically a 
flaw in the Python DB-API level. Even up2date drivers like psycopg2 for 
Postgres don't support something like PREPARE TRANSACTION or COMMIT 
PREPARED.

See also

<http://mail.zope.org/pipermail/zope3-users/2006-April/002949.html>

Looking back at your hack..it seems to introduce some more safety for a
particular usecase (perhaps general for people dealing only with one 
database at a time).

But thanks for pointing out this problem. I'll change my code in 
z3c.sqlalchemy in a similar way to gain at least a bit more safety.

Andreas
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