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

  • From: Tim Gorman <tim@xxxxxxxxxxxxx>
  • To: <oracle-l@xxxxxxxxxxxxx>
  • Date: Fri, 23 Apr 2004 12:06:31 -0600

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)

When do you see them?  Granted, you might want to live in my world (an
elevated part of the US called Colorado), but I didn't want to assume that
that is what you meant...  :-)


on 4/23/04 11:20 AM, Jesse, Rich at Rich.Jesse@xxxxxxxxxxxxxxxxx wrote:

> Man, I wish I lived in your world...
> 
> Rich
> 
> Rich Jesse                        System/Database Administrator
> rich.jesse@xxxxxxxxxxxxxxxxx      QuadTech, Sussex, WI USA
> 
> 
>> From: Tim Gorman
>> Sent: Friday, April 23, 2004 12:15 PM
>> 
>> The other two methods, FULL SCAN and FAST FULL SCAN, are not
>> often used
>> during queries, but are most often used during ALTER INDEX
>> ... REBUILD or
>> when index usage is explicitly hinted but not really
>> appropriate.
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