Re: CBO & disabled foreign keys

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Wed, 16 Mar 2005 22:13:19 +0000 (UTC)
Message-ID: <d1ab1v$62f$1@hercules.btinternet.com>

The optimizer can make use of them
if they are marked as 'RELY'.

It also helps if they columns are also
NOT NULL - if it's true, or course -
as this gives the optimizer more scope
for transforming queries.

-- 
Regards

Jonathan Lewis

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

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Public Appearances - schedule updated March 9th 2005






"Matthias Hoys" <idmwarpzone_NOSPAM__at_yahoo.com> wrote in message 
news:4238a847$0$30165$ba620e4c_at_news.skynet.be...


> Hi,

>

> Can the behaviour of the CBO be influenced by the presence of disabled 

> foreign key constraints ? Do disabled foreign key constraints have any use 

> at all ? I ask this because I noticed that in our Oracle 8i DWH db there 

> are a lot of disabled FK constraints. I wonder if I just can't remove 

> them, if they have no real use. Maybe they were created in this way to 

> influence CBO execution plans ?

>

>

> Thanks - Matthias

>

Received on Wed Mar 16 2005 - 16:13:19 CST