| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Andrew McMillan <Andrew(at)catalyst(dot)net(dot)nz> |
| Cc: | Matthias Urlichs <smurf(at)noris(dot)net>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: More Performance |
| Date: | 2000-05-21 01:59:04 |
| Message-ID: | 200005210159.VAA03127@candle.pha.pa.us |
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| Lists: | pgsql-hackers |
> > 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(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
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