Re: Performance / Index

On Thu, 13 Apr 2000 13:01:28 -0500, Terry Ball <terry_ball_at_csgsystems.com> wrote:

>If you use a percentage of 50, oracle will automatically do a compute so
>if you are going to use 50%, you might just as well compute.
>
>Mike Ault (who presents at IOUG and other places, and works for
>RevealNet) says he did extensive testing on this. He has proven to
>his satisfaction, that a sample of 30% is best. It gives more that
>adequate numbers with the least time. A smaller percentage does
>not give as close results and a higher percentage does not give any
>more accurate figurs while taking longer.
>

Careful, the situation is slightly different with low cardinality columns. The type that owuld be used in a bitmap index. Sometimes only a compute will do...  

Cheers
Nuno Souto
nsouto_at_nsw.bigpond.net.au.nospam
http://www.users.bigpond.net.au/the_Den/index.html Received on Fri Apr 14 2000 - 00:00:00 CDT