Re: CBO & disabled foreign keys

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Thu, 17 Mar 2005 20:42:53 +0000 (UTC)
Message-ID: <d1cq4d$ocq$1@titan.btinternet.com>

Yes,

    RELY/NORELY
    ENABLE/DISABLE
    VALIDATE/NOVALIDATE are three (virtually) independent options.

A constraint that is disabled/novalidate can still be RELY or NORELY.

If you want to leave FKs disabled on
a data warehouse, you may still want
to set them to RELY because this may
give the optimizer some options for
using particular transformation strategies during optimization.

-- 
Regards

Jonathan Lewis

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

http://www.jlcomp.demon.co.uk/seminar.html
Public Appearances - schedule updated March 9th 2005






"Matthias Hoys" <idmwarpzone_NOSPAM__at_yahoo.com> wrote in message 
news:4239dd1b$0$28062$ba620e4c_at_news.skynet.be...


>

> "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message 

> news:d1ab1v$62f$1_at_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

>>

>> http://www.jlcomp.demon.co.uk/seminar.html

>> Public Appearances - schedule updated March 9th 2005

>>

>>

>

> Is there a difference between fk constraints which have the status "RELY", 

> and those that are "DISABLED NOVALIDATE" ?

>

> Matthias

>

Received on Thu Mar 17 2005 - 14:42:53 CST