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Re: Why would an index not be used if specified as a hint in a query?

From: DA Morgan <damorgan_at_x.washington.edu>
Date: Fri, 11 Feb 2005 21:27:24 -0800
Message-ID: <1108185875.191030@yasure>


Craig & Co. wrote:

> Hi,
>
> Running Oracle 8.1.7.4 on Solaris 2.8.
>
> Running explain plan, and then a query (I don't have a copy to show at this
> point), apparently
> the index is not used.
>
> I assume it is because the optimiser thinks the index is not required even
> though it is specified.
>
> Cheers
> Craig.

A reasonable presumption.

On the other hand it could be lack of statistics for the optimizer or any one of a number of things. Small matters like the number of rows in the table, the applicability of the index to the query, the cardinality, and the percentage of rows to be returned could also be affecting the outcome.

-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)
Received on Fri Feb 11 2005 - 23:27:24 CST

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