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Date: Wed, 14 May 2003 08:45:10 -0400
Subject: Re: transactions in the SQLTransformer
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From: Brian Johnson <johnsbrn@yahoo.com>
To: cocoon-dev@xml.apache.org
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In-Reply-To: <3EC22C64.2010601@nada.kth.se>
Message-Id: <E66481BC-8609-11D7-9616-000393DB9A58@yahoo.com>

Interesting.... maybe it's an issue with XA vs. non-XA transactions. I 
haven't had the problem you describe with XA transactions. In my 
application, you would have to associate the connection with the 
session, since the SQLTransformer is used multiple times in the 
pipeline in a single transaction. What database are you using? I 
believe that transactions are associated with a particular thread, and 
since a second user request will always come in on a different thread, 
it shouldn't be an issue. Am I missing something? Is there a difference 
between XA and non-XA on this issue? Am I just wrong and simply haven't 
noticed the issue in my app? I wrote a test case for my application 
that I believe addresses the issue, but maybe I need to increase the 
number of concurrent connections to properly test it. Thanks.
Brian

On Wednesday, May 14, 2003, at 07:45  AM, Daniel Fagerstrom wrote:

> Brian Johnson wrote:
>
> > It should not be necessary to use the same connection for each query.
> > Even if you are not using a J2EE datasource, Cocoon maintains a pool
> > of database connections, so the connection is not actually closed
> > after each query. Transaction processing does not require a single
> > database connection, the only thing it requires is a single thread.
>
> I have tried this, IIRC it lead to some highly undesirable things like
> that an SQLTransformer instance that was serving another users request
> got a connection with an opened transaction from the pool and closed 
> it.
> As soon as you have more than one user it is very dangerous to return a
> connection with an opened transaction to the pool, you might be lucky
> and get the same connection when you executes the rest of the queries 
> in
> the transaction. But this "luck" is more likely when you as a developer
> is the only user.
>
> Anyhow as I wrote earlier in this thread I have written a patch
> http://issues.apache.org/bugzilla/show_bug.cgi?id=16718 that solve the
> problem, and also increase the efficiency of the SQLTransformer, and
> that works without any problems in our production systems since a 
> couple
> of mounths. I would be very thankful if somebody with commit right 
> could
> find the time to apply the patch :)
>
> /Daniel
>
>
>