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From "Dustin T. Clifford" <DCliff...@isdcorporation.com>
Subject RE: Query Compilation Drastically Increased on Join
Date Wed, 18 Feb 2009 19:28:49 GMT
Bryan,

This does look similar but I have noticed a difference. The estimated optimizer cost remains
exactly the same at 303.76 for whether joinOrder is specified or not. A colleague noted this
earlier today:

	I don't see the any differences between the cost based optimizer and the fix ordered query
plans, but the 	fix ordered is so much faster.  10.4.2 didn't help and an interesting thing
is that as I decrease the 	number of tables, the response time gets better which means sense
because of less permutation that it has 	to generate for query plan.  I'm not sure why the
query plans are the same, but the response times are so 	drastic unless I'm reading the query
plans incorrect or there is a bug that derby is not actually doing 	what is in the query plan.

Is this the same defect with slightly different symptoms maybe? Also, Jira does not note that
10.4, which we are using. Have you been able to reproduce your issue in 10.4?

Dustin

-----Original Message-----
From: Bryan Pendleton [mailto:bpendleton@amberpoint.com] 
Sent: Wednesday, February 18, 2009 2:09 PM
To: Derby Discussion
Subject: Re: Query Compilation Drastically Increased on Join

> offering.  We have recently modified a query by adding a couple of 
> tables to a simple join. We have noticed a drastic increase in query 
> compilation time on large data sets. 

It's possible you're seeing this problem:
https://issues.apache.org/jira/browse/DERBY-2130

There is an experimental patch attached to that issue. If possible,
in your environment, it would be interesting if you can confirm
whether the patch improves the behavior that you see.

thanks,

bryan


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