Re: Oracle Performance Tuning Question

The most common explanation of this behaviour is the limitation of the optimizer. When a query is too complex it chooses a common strategy, PK-index or Full table access. When you split up the query into five relatively simple ones, the optimizer algorithm is able to choose a real
efficient strategy.

regards,
Guus van de Sande

--
>
> On a relatively small data set on my local copy of Oracle, this takes
> roughly 13 seconds to return the correct data set. For non-trivial
> data sets, query performance will be completely unaacceptable.
> However, if I recode the query as a union of five queries, each for a
> single symbol, as below:
>
>
> the query comes back in roughly one second, perhaps less. Performance
> is quite good even with good sized data sets on a good-sized Sun
> server. Can anyone explain why there is over a factor of ten
> difference in performance between the two queries?
>
> Please respond via email as I do not read this newsgroup regularly.
>
> Sincerely,
> Mark W. Eaton
> Senior Engineering Manager, Application Server Development
> Harvest Technology, Inc.
> 164 Townsend
> Suite 2
> San Francisco, CA, 94107
> 415.908.6804 (phone)
> 415.777.4456 (FAX)
> eaton_at_harvestinc.com
>
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Received on Thu Sep 10 1998 - 14:19:48 CDT