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From Wernke zur Borg <>
Subject Re: Performance question [Problem solved!]
Date Wed, 25 Jan 2012 09:46:00 GMT

I solved the problem by wrapping the entire processing into one 
transaction, following "User-Defined Transaction Scope" in

         // embed the whole thing in one single transaction
         DataDomain d = getRuntime().getDataDomain();
         Transaction tx = d.createTransaction();

         try {
                 // do all processing here
         } finally {

No need to worry about rollbacks as everything is read-only.

 >>> Processing time has gone down from one hour to one minute !!!

Thanks to everybody,

On 2012-01-25 10:01, Wernke zur Borg wrote:
> To give you a picture here is a screenshot of the profiler showing 
> that one connection is opened and closed for every query.
> The question I do not understand is why does DataNode.performQueries() 
> unconditionally close the current connection?
> Otherwise I could probably provide a custom DataSource class 
> overriding getConnection() to re-use connections.
> Wernke
> On 2012-01-24 17:11, Wernke zur Borg wrote:
>> Dear list,
>> I have another question. My application converts a huge MS Access
>> database to a set of XML files by traversing some really big tables with
>> Select queries and also querying related tables to collect the
>> information needed for the output. Performance is horribly bad, so I did
>> some profiling and found that it spends 75% of its CPU time in
>> org.apache.cayenne.access.ExternalTransaction.close() and another 21% in
>> org.apache.cayenne.conn.DriverDataSource.getConnection(). Only 2% are
>> spent in SelectAction.performAction().
>> So it appears that it opens and closes a new connection for every single
>> select query. I must be doing something wrong here! Where can I tell it
>> to re-use connections? Or make one big transaction as it is read-only
>> anyway? Any other hints? I hope I can reduce the processing time to 4%
>> of what it is now...
>> Thanks,
>> Wernke

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