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Home -> Community -> Usenet -> c.d.o.misc -> Re: Oracle wont use an index and performance sucks
PMJI, but with cost based optimization the cardinality of the indexes counts.
If your keys are not spread out enough, then the cost of an index search can
be higher than for a table scan. You may need to use hints.
In article <19990207132645.13258.00000003_at_ngol03.aol.com>,
gjlinker_at_aol.com (Gjlinker) wrote:
>
> Dear all,
>
> >Since we upgraded to 805 from 733 a month ago
> >we have been having performance problems, not across every tbale but on
> >certain specfic tables.
>
> Oracle has re-implemented the optimizer in Oracle8. The optimizer did not work
> very well in Oracle7. My experience is that you can have a query like the one
> you described to use the index when no compute statistics is used. When you
> compute statistics it will start doing full table scans.
>
> Oracle support told me that all should be fine in Oracle8. Apparently it
> isn't...
>
> Regards Gerrit-Jan Linker,
>
> *************************************************
> *| Gerrit-Jan Linker : gjlinker_at_aol.com
> *|
> *| http://members.aol.com/gjlinker
> *|
> *| Developer of:
> *| Oraxcel, OraWeb, OraSQL, OraCodes and OraDebug
> *************************************************
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> LLLL
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> L Linker IT Consulting Ltd L
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>
>
Joseph R.P. Maloney, CCP,CSP,CDP
MPiR, Inc.
502-451-7404
some witty phrase goes here, I think.
-----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own Received on Mon Feb 08 1999 - 08:26:57 CST