Re: Group-count estimation statistics

* Tom Lane (tgl(at)sss(dot)pgh(dot)pa(dot)us) wrote:
> The only real solution, of course, is to acquire cross-column
> statistics, but I don't see that happening in the near future.

That'd be nice, but sounds like alot of work.

> As a short-term hack, I am thinking that the "clamp to size of table"
> part of the rule is overly pessimistic, and that we should consider
> something like "clamp to size of table / 10" instead. The justification
> for this is the thought that you aren't going to bother grouping unless
> it actually reduces the data volume. We have used similar rules in the

I definitely agree with this.

Stephen