RE: oracle can ignore hints
- From: "Lim, Binley" <Binley.Lim@xxxxxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 8 Mar 2004 15:43:35 +1300
IIRC, RBO had that thing where in the event of an index-tie (2 indexes
qualify equally according to the rules), the index with a later creation
date(or is it earlier?) is picked.
> -----Original Message-----
> From: Jared Still [SMTP:jkstill@xxxxxxxxxx]
> Sent: Saturday, March 06, 2004 3:58 AM
> To: Oracle-L Freelists
> Subject: Re: oracle can ignore hints
>
> I have had that exact same experience.
>
> Two Sun servers, different number of CPU's and RAM,
> same versions of Oracle 7 down to the patch level,
> data exported from one database into the other.
>
> Strictly RBO, two very different execution paths.
>
> Very frustrating, wish I could recall the solution we used.
>
> Jared
>
>
>
>
> On Fri, 2004-03-05 at 00:41, Kresimir Fabijanic wrote:
> > Hi Ryan
> >
> > What version of Oracle and OS are you running? What hint did you try to
>
> > use? How complex was query?
> >
> > I have seen a case (OK it was 7.3.4.0 in 1999 on Sun's OS) where two
> > databases - same version, same OS same Oracle and OS patches on both -
> > hardware configuration was slightly different (not 100% sure but there
> > were differences in RAM (1G vs 2G or 4G) and number of CPUs - (2 vs 4)
> > and some disk layout differences) both databases running RULE (software
> > vendor requested [Keystone - if you have ever heard of it]) - identical
> > statement (cut and paste between two terminal sessions (and back))
> > generating very different execution plans.
> >
> > I tried to verify few times and results were consistently different.
> > Nothing would surprise me any more.
> >
> > Kind regards
> >
> > Kresimir Fabijanic
> >
> > ryan.gaffuri@xxxxxxx wrote:
> >
> > >We had a discussion on here regarding hints. some of you stated that
> Oracle cannot ignore a proper hint. I have a TAR open and asked about
> this. Here is the response.
> > >
> > >
> > >
> > >"A hint simply adds weight to a cost estimation, it can still be
> overridden by the CBO if the values aren't seen as useful."
> > >
> > >
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