Re: Assertion failure with LEFT JOINs among >500 relations

On Sat, 17 Oct 2020 at 06:00, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I'm confused now, because the v2 patch does remove those isnan calls?

I think that was a case of a last-minute change of mind and forgetting
to attach the updated patch.

> I rechecked the archives, and I agree that there's no data about
> exactly how we could have gotten a NaN here. My guess though is
> infinity-times-zero in some earlier relation size estimate. So
> hopefully the clamp to 1e100 will make that impossible, or if it
> doesn't then clamp_row_est() should still prevent a NaN from
> propagating to the next level up.
>
> I'm good with the v2 patch.

Thanks a lot for having a look. I'll proceed in getting the v2 which I
sent earlier into master.

For the backbranches, I think I go with something more minimal in the
form of adding:

if (outer_path_rows <= 0 || isnan(outer_path_rows))
outer_path_rows = 1;
+else if (isinf(outer_path_rows))
+ outer_path_rows = DBL_MAX;

and the same for the inner_path_rows to each area in costsize.c which
has that code.

Wondering your thoughts on that.

David