RE: Index scan and redundant sorting

From: Niall Litchfield <n-litchfield_at_audit-commission.gov.uk>
Date: Wed, 25 Feb 2004 23:38:46 +0000
Message-Id: <s03d3213.062@bristol21.bristol.ac>

That is my understanding too.

-----Original Message-----
From: AC.GWIA.oracle-l_at_freelists.org [mailto:AC.GWIA.oracle-l_at_freelists.org] Sent: Wed 25/02/2004 20:10
To: Daniel.Fink_at_Sun.COM; oracle-l_at_freelists.org Cc:
Subject: Re: Index scan and redundant sorting

Let's see if I understand correctly. For an IFS or IRS, the blocks of an index are read (in single block read mode) in the order of their existence within the tree. For an IFFS, all blocks in the segment (below the HWM) are read in order of their 'physical' existence within the segment. This is not the order of their existence within the tree, so the blocks are 'out of order'.

Dan

"Bobak, Mark" wrote:

> Dan,Only an INDEX FULL SCAN (walks the tree, does single
> block reads) provides sorted output.An INDEX FAST FULL SCAN
> (does not walk tree structure, does multi-block reads,
> discards branch blocks) does NOT provide sorted output.-Mark
>
> Mark J. Bobak
> Oracle DBA
> ProQuest Company
> Ann Arbor, MI
> "Imagination was given to man to compensate him for what he is
> not, and a sense of humor was provided to console him for what
> he is." --Horace Walpole

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Received on Wed Feb 25 2004 - 17:35:58 CST