| From: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
|---|---|
| To: | mlw <markw(at)mohawksoft(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Thomas Lockhart <thomas(at)fourpalms(dot)org>, Lincoln Yeoh <lyeoh(at)pop(dot)jaring(dot)my>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Louis-David Mitterrand <vindex(at)apartia(dot)org>, PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Index Scans become Seq Scans after VACUUM ANALYSE |
| Date: | 2002-04-17 18:32:19 |
| Message-ID: | Pine.LNX.4.30.0204171428300.690-100000@peter.localdomain |
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| Lists: | pgsql-hackers |
mlw writes:
> Adding huristics, such as weighting for index scans, is not making the planner
> stupider. It is making it smarter and more flexable.
If life was as simple as index or no index then this might make some
sense. But in general the planner has a whole bunch of choices of join
plans, sorts, scans, and the cost of an individual index scan is hidden
down somewhere in the leaf nodes, so you can't simply say that plans of
type X should be preferred when the cost estimates are close.
--
Peter Eisentraut peter_e(at)gmx(dot)net
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