Re: wildcard search and full tablescans

Charles Hooper wrote:

> Paraphrasing from "Expert Oracle Database Architecture" by Tom Kyte:
> B*Tree indexes should be used only when retrieving a small portion of
> the rows in a table - less than 20% of the rows.

Oh I know Tom wrote that and I suspect he regrets having done so. Not because it isn't often correct ... but because often it is not correct.

I can, for example, fiddle with optimizer_index_cost_adj and optimizer_index_caching and make that number come out just about anywhere I want.

Remember Connor's demo of how he could dial in just about any hit ratio he wanted? Somewhere I have one that does the same thing with B*Trees. I'll see if I can find it.

Regards

-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace x with u to respond)
Puget Sound Oracle Users Group
www.psoug.org