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From "Bergquist, Brett" <BBergqu...@canoga.com>
Subject RE: I need help diagnosing a Derby engine problem where threads are not progressing
Date Fri, 14 Mar 2014 14:19:00 GMT
Unfortunately, introducing something into the production environment is not possible.  I am
in the process of trying to build a simulation of that environment but that is also difficult
as the application is an Element Management System and in the network there are about 40K
pieces of our equipment that are being monitored and receiving data from with provisioning
of additional services on the equipment or new equipment ever few minutes.  Getting a lab
setup with that is being a challenge (simulating 40K pieces of IP addressable equipment that
responds to management request via SNMP is not trivial).

But the patch will give me an idea of where you were looking.   So from the comment in the
JIRA, it appears that you were testing with a hard limit to the optimizer timeout.   So am
I correct that in the 10.9 release timeframe, there is no such hard limit?

-----Original Message-----
From: Bryan Pendleton [mailto:bpendleton.derby@gmail.com] 
Sent: Friday, March 14, 2014 10:10 AM
To: derby-dev@db.apache.org
Subject: Re: I need help diagnosing a Derby engine problem where threads are not progressing

>>> My assumption is that there is a possibility that the optimization 
>>> may get into a state where it may take a very long time to complete 
>>> or may even be looping.

>>> So what I would like to explore is under what conditions could the 
>>> optimizer get into a state where it might loop or make no progress 
>>> for a very long period of time.

Are you able to try the patch for DERBY-2130 in your environment?

https://issues.apache.org/jira/browse/DERBY-2130

At the time that I was wrestling with this problem (years ago, sorry), I was experiencing
great instability in optimization times.

Sometimes it would run in a few seconds.

Sometimes it would take 15 minutes.

If you can provide any feedback on whether the DERBY-2130 change alters the behaviors that
you see, that would be great!

bryan


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