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problem with query optimizer

2 posts in Windows NT Last posting was on 2001-01-18 21:22:21.0Z
Milan_Mircetic Posted on 2001-01-18 17:42:14.0Z
From: Milan_Mircetic
Date: Thu, 18 Jan 2001 12:42:14 -0500
Newsgroups: sybase.public.sqlserver.nt
Subject: problem with query optimizer
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Hi!
We have a version ASE 11.9.2/1031/P/NT(ix86)/03
Our queries become real slow by time even we update statistics every day.
When check plan with showplan we find totaly different showplan for the
query comparing with showplan when query ran well, then we have to add
dummy index to revert to old good showplan and then drop dummy index and
after a month same thing happens again.
Is this Sybase internal bug in this release or what?

Thanks


Eric Miner Posted on 2001-01-18 21:22:21.0Z
Message-ID: <3A675E8D.407A8F2B@sybase.com>
Date: Thu, 18 Jan 2001 13:22:21 -0800
From: Eric Miner <eminer@sybase.com>
Organization: Sybase, Inc.
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Article PK: 1088760

Milan,

You'll need to supply more information so that we can help you with analysis
of this situation.

Update statistics does not guarantee good performance, only that the
statistics are up to date as of the end of its run. I suspect there are
changes to the stats that are effecting which query plan is being chosen.

Could you post the following:
dbcc traceon(3604,302,310) output for a run of the query when thins run fine
and when it's slow

Optdiag for the table before and after you run update stats
The update stats syntax you're using
The query.

Thanks,

Eric Miner
Sybase
ESD Engineering
Optimizer Group

Milan_Mircetic wrote:

> Hi!
> We have a version ASE 11.9.2/1031/P/NT(ix86)/03
> Our queries become real slow by time even we update statistics every day.
> When check plan with showplan we find totaly different showplan for the
> query comparing with showplan when query ran well, then we have to add
> dummy index to revert to old good showplan and then drop dummy index and
> after a month same thing happens again.
> Is this Sybase internal bug in this release or what?
>
> Thanks