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Home -> Community -> Mailing Lists -> Oracle-L -> 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_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Mladen Gogala
Sent: Wednesday, March 03, 2004 8:23 AM
To: oracle-l_at_freelists.org
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_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Wolfgang Breitling
> Sent: Monday, March 01, 2004 10:30 PM
> To: oracle-l_at_freelists.org
> 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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-- Archives are at http://www.freelists.org/archives/oracle-l/ FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html ----------------------------------------------------------------- ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request_at_freelists.org put 'unsubscribe' in the subject line. -- Archives are at http://www.freelists.org/archives/oracle-l/ FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------Received on Wed Mar 03 2004 - 09:52:52 CST
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