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RE: index full scan over an index fast full scan in an analytic function?

From: Larry Elkins <elkinsl_at_flash.net>
Date: Thu, 23 Oct 2003 13:19:25 -0800
Message-ID: <F001.005D4213.20031023131925@fatcity.com>


Possibly to avoid a sort operation (assuming that you might be able to get away with a NOSORT when doing the full index scan)? It might be deciding that the benefit of the multi-block reads for the fast full scan are more than offset by the sort operation that would be needed (and might not be needed when doing the full index scan).

Regards,

Larry G. Elkins
The Elkins Organization Inc.
elkinsl_at_flash.net
214.954.1781

> -----Original Message-----
> From: ml-errors_at_fatcity.com [mailto:ml-errors_at_fatcity.com]On Behalf Of
> rgaffuri_at_cox.net
> Sent: Thursday, October 23, 2003 2:39 PM
> To: Multiple recipients of list ORACLE-L
> Subject: Re: index full scan over an index fast full scan in an analytic
> function?
>
>
> i cant attach the 10053 trace. it has proprietary info. There
> isnt much in analytic explain plan either.
>
> does anyone know in general why a full scan would be faster than
> a fast full scan?
> >
> > From: <rgaffuri_at_cox.net>
> > Date: 2003/10/23 Thu PM 03:09:26 EDT
> > To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > Subject: index full scan over an index fast full scan in an
> analytic function?
> >
> > I have an index on the two columns used in this query. Why
> would the optimizer choose an index full scan over an index fast
> full scan?
> >
> > My question isnt why an index is used, but the type of index scan?
> >
> > select *
> > from (select col1, col2,
> > dense_rank()
> > over (partition by col1
> > order by col2 desc)tab
> > from mytable)
> > where tab = 1
> >
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.net
> > --
> > Author: <rgaffuri_at_cox.net
> > INET: rgaffuri_at_cox.net
> >
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> Author: <rgaffuri_at_cox.net
> INET: rgaffuri_at_cox.net
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Larry Elkins
  INET: elkinsl_at_flash.net

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San Diego, California        -- Mailing list and web hosting services
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Received on Thu Oct 23 2003 - 16:19:25 CDT

Original text of this message

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