RE: RE: query slow in 9i, but not slow in 8i

From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Date: Wed, 3 Mar 2004 13:20:36 -0500
Looks like you got a reply too.  By the way, his name is Cary, not Carrie. ;-)

-----Original Message-----
From: ryan.gaffuri@xxxxxxx [mailto:ryan.gaffuri@xxxxxxx]
Sent: Wednesday, March 03, 2004 11:47 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: RE: RE: query slow in 9i, but not slow in 8i


i put this on asktom and did a name drop to ensure a response(hope that was 
ok). 

http://asktom.oracle.com/pls/ask/f?p=4950:8:4690129998850851286::NO::F4950_P8_DISPLAYID,F4950_P8_CRITERIA:707586567563,

my post is at the bottom of the thread. 
> 
> From: "Cary Millsap" <cary.millsap@xxxxxxxxxx>
> Date: 2004/03/03 Wed AM 10:50:30 EST
> To: <oracle-l@xxxxxxxxxxxxx>
> Subject: RE: RE: query slow in 9i, but not slow in 8i
> 
> Not a big query at all. If I recall correctly, the query ran in about a
> minute and a quarter--something like 1:15.0, with 1:14.5 consumed in the
> parse. It was some kind of a bug, but I can't remember which. Now that I
> think about it, I'm not even sure whether it was histograms or
> partitions that was causing the problem. Not a lot of value, this foggy
> anecdote of mine :).
> 
> 
> Cary Millsap
> Hotsos Enterprises, Ltd.
> http://www.hotsos.com
> * Nullius in verba *
> 
> Upcoming events:
> - Performance Diagnosis 101: 3/23 Park City, 4/6 Seattle
> - Hotsos Symposium 2004: March 7-10 Dallas
> - Visit www.hotsos.com for schedule details...
> 
> 
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Mladen Gogala
> Sent: Wednesday, March 03, 2004 8:23 AM
> To: oracle-l@xxxxxxxxxxxxx
> Subject: Re: RE: query slow in 9i, but not slow in 8i
> 
> Parse time over a minute? Was it a huge query or not? I find it hard to
> believe.
> 
> 
> On 03/02/2004 09:36:10 PM, Cary Millsap wrote:
> > I don't have access to the data to back this up, but I have seen PARSE
> > call response time move from over a minute to less than a second by
> > eliminating histograms from the equation. I think when I last saw
> this,
> > it was an Oracle8 system.
> > 
> > 
> > Cary Millsap
> > Hotsos Enterprises, Ltd.
> > http://www.hotsos.com
> > * Nullius in verba *
> > 
> > Upcoming events:
> > - Performance Diagnosis 101: 3/23 Park City, 4/6 Seattle
> > - Hotsos Symposium 2004: March 7-10 Dallas
> > - Visit www.hotsos.com for schedule details...
> > 
> > 
> > -----Original Message-----
> > From: oracle-l-bounce@xxxxxxxxxxxxx
> > [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Wolfgang Breitling
> > Sent: Monday, March 01, 2004 10:30 PM
> > To: oracle-l@xxxxxxxxxxxxx
> > Subject: Re: RE: query slow in 9i, but not slow in 8i
> > 
> > There surely is some "cost" involved in evaluating a histogram during
> > the 
> > parse phase, but I doubt that it will be significant enough to be 
> > measurable. But histograms change the estimates of the CBO and it is
> > quite 
> > possible that the presence of a histogram on a column where the
> content
> > is 
> > not skewed enough to really warrant a histogram can change the
> estimates
> > 
> > enough to cause the optimizer to use a different, slower access path
> > than 
> > without the histogram.
> > 
> > At 09:14 PM 3/1/2004, you wrote:
> > 
> > >I am unfortunately speaking from heresay, however I heard once that
> > having
> > >histograms all over the place can slow down parsing as they have to
> be
> > >inspected.  I was left with the impression that unless the data is
> > skewed
> > >enough to warrant a histogram then there actually is a negative cost
> > >associated with having too many histograms.
> > >
> > >Surely someone on this list can either support me or shoot me down on
> > this
> > >one?
> > 
> > Wolfgang Breitling
> > Oracle7, 8, 8i, 9i OCP DBA
> > Centrex Consulting Corporation
> > http://www.centrexcc.com 
> > 
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RE: RE: query slow in 9i, but not slow in 8i

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