> > We can't read data from the index.  It would be nice if we could, but we
> > can't.  I think we believe that there are very few cases where this
> > would be win.  Usually you need non-indexed data too.
> 
> I have used other databases where this _is_ possible in the past, and
> the win is big when the programmer codes for it.  Sure, most cases don't
> just use indexed data, but if the programmer knows that the database
> supports index-only scans then sometimes an extreme performance
> requirement can be met.
> 

Yes, totally true.  It is an extreme optimization.  In Ingres, you could
actually SELECT on the index and use that when needed.

-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
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Sat, 20 May 2000 21:59:04 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: More Performance