From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | mlw <markw(at)mohawksoft(dot)com> |
Cc: | Andrew Sullivan <andrew(at)libertyrms(dot)info>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Index Scans become Seq Scans after VACUUM ANALYSE |
Date: | 2002-04-17 21:13:04 |
Message-ID: | 200204172113.g3HLD4w03659@candle.pha.pa.us |
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Lists: | pgsql-hackers |
mlw wrote:
> Andrew Sullivan wrote:
>
> > > Now, given the choice of the two strategies on a table, both pretty
> > > close to one another, the risk of poor performance for using the
> > > index scan is minimal based on the statistics, but the risk of poor
> > > performance for using the sequential scan is quite high on a large
> > > table.
> >
> > I thought that's what the various cost estimates were there to cover.
> > If this is all you're saying, then the feature is already there.
>
> The point is that if the index plan is < 20% more costly than the sequential
> scan, it is probably less risky.
I just posted on this topic. Index scan is more risky, no question
about it.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
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