Re: Cache hit rate

From: John P. Higgins <jh33378nospam_at_deere.com>
Date: Tue, 19 May 1998 21:02:34 -0500
Message-ID: <356239BA.BA02AE4E@deere.com>

Some cases one, some cases the other. With rules based optimizer, Oracle always uses an index if it is available and mentioned in the where clause. The cost based optimizer, based on the statistics from the analyze command, will properly switch to a full table scan when benificial.

larionov_at_yahoo.com wrote:

> How about the range queries? Suppose there is an index on a table,
> but I use the range query (like select sum...) which scans about half of the
> table. Does oracle use multiblock_read_count in this case or
> it still thinks this is the query via index lookup?
>
> Thank you!
>
> "Pei L. Ku" <pku_at_gte.net> wrote:
> >
> > Oracle uses multiblock_read_count for full table scan only. If the rows
> > you are updating are fetched via index lookup, multiblock_read_count does
> > not come into play.
> >
> > Pei
> >
>
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Received on Tue May 19 1998 - 21:02:34 CDT