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

  • From: "Ryan" <ryan.gaffuri@xxxxxxx>
  • To: <oracle-l@xxxxxxxxxxxxx>
  • Date: Mon, 1 Mar 2004 16:51:50 -0500

yeah good idea. how do you determine which columns need histograms? I have
100s of tables in my applications and I do not have time to determine it. I
typically have them run over night.
----- Original Message ----- 
From: "Wolfgang Breitling" <breitliw@xxxxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Monday, March 01, 2004 2:17 PM
Subject: Re: RE: query slow in 9i, but not slow in 8i


> I would NOT do that. "method_opt='FOR ALL COLUMNS'" will collect
histograms
> of (default) size 75 for ALL columns of the table. At best that would be a
> waste of time and resources, but it could easily be rather detrimental to
> access paths. You do NOT want to collect histograms unless it is
warranted.
>
> If the columns did not have histograms in 8i, I would not suddenly create
> any in 9i.
>
> At 11:55 AM 3/1/2004, you wrote:
> >then you did not properly analyze the tables. look at the cardinality in
> >the plan.
> >
> >card=estimated rows. estimated runs is determined by dba_tables.num_rows
> >which is populated when tables are analyzed.
> >
> >do the following
> >
> >exec
>
>dbms_stats_gather_table_stats(ownname=>'blah',tabnam=>'blah',method_opt='FO
R
> >ALL COLUMNS',cascade=>true);
> >
> >on both tables in 9204.
>
> Wolfgang Breitling
> Oracle7, 8, 8i, 9i OCP DBA
> Centrex Consulting Corporation
> http://www.centrexcc.com
>
>
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