Re: More stable query plans via more predictable column statistics

On Wed, Mar 9, 2016 at 5:28 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "Shulgin, Oleksandr" <oleksandr(dot)shulgin(at)zalando(dot)de> writes:
> > Yes, I now recall that my actual concern was that sample_cnt may
> calculate
> > to 0 due to the latest condition above, but that also implies track_cnt
> ==
> > 0, and then we have a for loop there which will not run at all due to
> this,
> > so I figured we can avoid calculating avgcount and running the loop
> > altogether with that check. I'm not opposed to changing the condition if
> > that makes the code easier to understand (or dropping it altogether if
> > calculating 0/0 is believed to be harmless anyway).
>
> Avoiding intentional zero divides is good. It might happen to work
> conveniently on your machine, but I wouldn't think it's portable.
>

Tom,

Thank you for volunteering to review this patch!

Are you waiting on me to produce an updated version with more comments
about NULL-handling in the distinct estimator, or do you have something
cooking already?

--
Regards,
Alex