| From: | "Thomas G(dot) Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu> |
|---|---|
| To: | Jan Wieck <jwieck(at)debis(dot)com> |
| Cc: | Andreas Zeugswetter <andreas(dot)zeugswetter(at)telecom(dot)at>, hackers(at)postgreSQL(dot)org |
| Subject: | Re: [HACKERS] Re: order by and index path |
| Date: | 1998-10-15 14:28:36 |
| Message-ID: | 36260694.9139563E@alumni.caltech.edu |
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| Lists: | pgsql-hackers |
> We do not have this statistical information. So the whole
> thing is at this time academic.
I recall that Commercial Ingres made the assumption that one row (or 1%
of rows? My memory of Ingres is fading :) would be returned from a
qualified query if no statistics were available to suggest otherwise.
It did collect statistics on data distribution to try to help make those
optimizer choices.
It may be reasonable to assume that if there is an index, then using it
with any qualified query would be a win. Since the alternative is to
decide to _not_ use an index, a decision for which we have no support
with existing statistics.
- Tom
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