Re: cost

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Tue, 6 Apr 2004 09:37:55 +0100
Message-ID: <00c201c41bb2$7a4dbc60$7102a8c0@Primary>

Me, too.
I should have tested it before I emailed.

But I'm pretty sure there is an 8.1.7 version where the result would not appear - although I am only basing this claim on the memory of just a few years ago where the optimizer calculated a cardinality of 1, and joined to the next table using a nested loop FTS. Unfortunately the actual cardinality was not one, so the nested loop option was much more resource intensive than the hash join when it ran.

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

April 2004 Iceland http://www.index.is/oracleday.php June 2004 UK - Optimising Oracle Seminar

• Original Message ----- From: "Wolfgang Breitling" <breitliw_at_centrexcc.com> To: <oracle-l_at_freelists.org> Sent: Tuesday, April 06, 2004 1:48 AM Subject: Re: cost

I get the same result (higher cost hash join chosen over NL join) with Oracle 8.1.7.4.1

At 01:28 PM 4/5/2004, you wrote:

>My guess would be that this is a deliberate
>heuristic introduced some time around 9
>to avoid nested loop full tablescans when
>the numbers are small.

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Received on Tue Apr 06 2004 - 03:34:30 CDT