Re: OCP - Performance Tuning

From: Niall Litchfield <n-litchfield_at_audit-commission.gov.uk>
Date: Wed, 29 Jan 2003 10:03:16 -0000
Message-ID: <3e37a6e4$0$245$ed9e5944@reading.news.pipex.net>

"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message news:b181rj$m9g$1$8302bc10_at_news.demon.co.uk...
> It is very easy to produce an example
> where changing the number of rows
> (without changing the number of blocks)
> in one of the tables causes a change in
> the execution path between merge join
> and nested loop join.
>

I'd be interested to see this, as the only way I can imagine the CBO taking the number of rows into account would be if there was an index access path (and hence selectivity changed), which may well be a good assumption but indexes are not referred to at all in the question.

>
> Helpful Hints for OCP (1) - if you are asked
> to select one option, but you know that two
> of the options are correct, the expected
> response might be one of the incorrect options.
>

:(, and of course if the correct answer is e) None of the above.....

--
Niall Litchfield
Oracle DBA
Audit Commission UK

Received on Wed Jan 29 2003 - 04:03:16 CST