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RE: which should be faster

From: Stephane Paquette <stephane.paquette_at_standardlife.ca>
Date: Mon, 05 May 2003 07:52:08 -0800
Message-ID: <F001.0058F855.20030505075208@fatcity.com>


I've check on asktom and he is positive that the order of predicate has no impact (DB version for that comment is 815).
>From the site :

No, the order of evaluation of a predicate in SQL is purposely "indeterminate".

You should not, cannot rely on a specific order or evaluation. You cannot even
rely on short-circut evaluation. The optimizer will evaluate the predicate in
the order it feels is best -- that is its job.

SQL is a wholly non-procedural language, you are trying to attribute procedural
language to it. You should not have any need to have a predicate evaluated in
some order.

If anyone can come up with a good reason for needing a predicate evaluated in
some specific order -- put it in the comments and I'll address them as they come
in.

Stephane
-----Original Message-----
Sent: Saturday, May 03, 2003 1:52 PM
To: Multiple recipients of list ORACLE-L

Is the predicate order relavent for 8.1.7.3? Im doing quite a bit of tuning and am wondering whether its worth the effort to reorganize the predicate?

So is the rule of thumb on predicates.

 Filters before joins..

If I have col1 = 'ABC', put that before my join?

BTW, logically I would think it would help to put filters into inline views, but Im not seeing any performance improvements. You have any luck with this?

select col1, b.col2
from a,
(select col2
from tabb
where col2 = 'blah') b
where a.col1 = b.col1

Someone told me this can help. Any good rules of thumb on this or documents? All the books seem to only focus on the basic things. ----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Saturday, May 03, 2003 11:11 AM

>
> Did you also test with index compression in place
> on the organization column ?
>
> If your tests were:
> organization = 'XXX'
> and inv_date between ....
>
> did you also test
> inv_date between ....
> and organization = 'XXX'
>
> Under Oracle 8, the predicate order
> can make a difference - although in
> this case I don't think you would see
> much difference, as neither predicate
> is an eliminator at the filter level.
>
>
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> The educated person is not the person
> who can answer the questions, but the
> person who can question the answers -- T. Schick Jr
>
>
> One-day tutorials:
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>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: 02 May 2003 22:31
>
>
> > Actually I found a note on tom kyte's book(expert one on one) that
> it
> > shouldn't matter weather u index c1,c2 or c2,c1 . Although my
> scenerio is
> > not exact . But its kinda similer . I did a little testing and found
> that
> > just invdate is faster compare to org , indate .
> >
> > Thanks ,
> > -ak
> >
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Jonathan Lewis
> INET: jonathan_at_jlcomp.demon.co.uk
>
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--
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--
Author: Ryan
  INET: rgaffuri_at_cox.net

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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Stephane Paquette
  INET: stephane.paquette_at_standardlife.ca

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Received on Mon May 05 2003 - 10:52:08 CDT

Original text of this message

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