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Re: Optimizer issue

From: Manjula Krishnan <>
Date: Fri, 19 May 2006 10:47:46 -0500
Message-ID: <>

I quote the vendor "the potential for displaced data (missing data on forms and reports) where statistics have been gathered. Missing data has been observed within the application under a strict RULE based environment where objects have been analyzed to gather statistics." What Riyaj said makes sense that without the order by clause, it will "appear" like data is missing.

Riyaj: What did you mean by "code/strategy that will break" ?

Thanks yall.


On 5/19/06, Riyaj Shamsudeen <> wrote:
> Quoting Manjula:
> >>and some data would not be pulled up in the application. Is that
> possible?
> Huh ? Generally not possible. But, I know of one exception. I think
> Kirti Deshpande encountered this: One of the application was relying
> upon an index order to return the rows in a specific order. Optimizer
> selected a different index, after collecting statistics, affecting the
> functionality. Specifically, if the code is also interested in top N
> rows with this strategy, then incorrect (from the application point of
> view) will be pulled in to the application, causing user irritation.
> But, the problem here is that incorrect and potentially treacherous
> strategy. Unless 'order by' clause is used, RDBMS will return rows
> anyway it sees fit. So, you might want to ask them to provide more
> details as to exactly why collecting statistics will not work and ask
> for code/strategy that will break.
> --
> Thanks
> Riyaj "Re-yas" Shamsudeen
> Certified Oracle DBA (ver 7.0 - 9i)
> Allocation & Assortment planning systems
> JCPenney
> Manjula Krishnan wrote:
> > I have an application on Oracle 9i. The database (designed by the
> > vendor) was set with optimizer_mode=CHOOSE. A week after we went live
> > with the application, performance started degrading. I discovered that
> > statistics were missing and built them. Immediately the application
> > problems were resolved.
> >
> > The vendor claims that with the statistics, it would not use the right
> > indexes and some data would not be pulled up in the application. Is
> > that possible?
> >
> > Thanks,
> >
> > Manjula
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Received on Fri May 19 2006 - 10:47:46 CDT

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