From: mlw <markw@mohawksoft.com>
11:05
Subject: Re: Index Scans become Seq Scans after VACUUM ANALYSE To: Thomas Lockhart
<thomas@fourpalms.org>
Thomas Lockhart wrote:
>
> ...
> > Weighing these factors, perhaps once we get one or two complaining about
> > postgresql using an index vs 20 complaining about not using an index, then
> > the optimizer values have reached a good compromise :). But maybe the ratio
> > should be 1 vs 100?
>
> :)
>
> So we should work on collecting those statistics, rather than statistics
> on data. What do you think Tom; should we work on a "mailing list based
> planner" which adjusts numbers from, say, a web site? That is just too
> funny :)))
No, you miss the point!
On borderline conditions, wrongly using an index does not result in as bad
performance as wrongly not using an index, thus usage of an index should be
weighted higher because the risk of not using the index out weighs the risk of
using it.