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Re: Why "Separating Data and Indexes improves performance" is a m yth?

From: Mladen Gogala <>
Date: Fri, 23 Apr 2004 14:20:24 -0400
Message-ID: <>

On 04/23/2004 02:06:31 PM, Tim Gorman wrote:
> Do you see a lot of FAST FULL scans? Generally, when I see them, they are
> the result of either:
> * SELECT COUNT(*) on table with PK (usually ad-hoc, thus rare)
> * result of index being forced into usage due to an inappropriate
> INDEX hint (i.e. no predicates using the index in the WHERE
> clause)
> * ALTER INDEX ... REBUILD (hopefully relatively rare)

Another situation in which fast full scans appear is a report from a reference table, like a list of names of all employees (artificial example, but I have no better at the moment). Those are relatively rare, but they are regular. Speaking of index scans, does anybody here sees skip scans? Few months ago I've had a lengthy discussion with Wolfgang about INDEX_SS, but I have to confess that I've never seen them in real life.

Mladen Gogala
Oracle DBA

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Received on Fri Apr 23 2004 - 13:19:47 CDT

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