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From "Dustin T. Clifford" <DCliff...@isdcorporation.com>
Subject RE: Slow performance on 5 or more joins in a star schema
Date Wed, 29 Jul 2009 22:05:11 GMT
Thanks for your reply. I hope to see this enhancement in the near future. Derby has performed
well for our customers and ourselves for quite some time and a more robust optimizer would,
definitely, help us to continue suggesting Derby as a reasonable alternative to Oracle and
SQL Server. Please, don't mistake my last statement as an insult as we understand that the
community works as hard as it can to provide this amazing solution. We would like to thank
the Derby community for their efforts! We do appreciate it!

-----Original Message-----
From: Richard.Hillegas@Sun.COM [mailto:Richard.Hillegas@Sun.COM] 
Sent: Wednesday, July 29, 2009 9:08 AM
To: Derby Discussion
Subject: Re: Slow performance on 5 or more joins in a star schema

Hi Dustin,

As you note, the Derby query optimizer only considers left-deep trees. I 
have logged an enhancement request for support for bushy query plans: 
DERBY-4327. If many people vote for this issue, we can consider it for 
the next Derby feature release.


Dustin T. Clifford wrote:
> All,
> We have implemented a star schema and we are noticing that queries 
> involving 5 or more joins perform very slowly. We have, also, noticed 
> that batch updates and deletes perform slowly. We support multiple 
> databases and, as we improve on performance in SQL Server and Oracle, 
> we notice a trend in the opposite direction with Derby.
> I know that the Derby optimizer use to only consider  left-deep 
>  trees. Is this still true or is there another optimizer that we can 
> use? Does anybody have any advise on working in a manner that can 
> provide good performance on Derby, SQL Server and Oracle? Any advice 
> would be appreciated.
> *Dustin Clifford*

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