Re: Assertion failure with LEFT JOINs among >500 relations

David Rowley <dgrowleyml@gmail.com> writes:
> I admit it's annoying to add cycles to clamp_row_est() for such insane cases.

I poked at this a bit more closely, and noted that the actual problem is
that when we do this:

    outer_skip_rows = rint(outer_path_rows * outerstartsel);

we have outer_path_rows = inf, outerstartsel = 0, and of course inf times
zero is NaN.  So we end up asserting "NaN <= Inf", not "Inf <= Inf"
(which wouldn't have caused a problem).

If we did want to do something here, I'd consider something like

    if (isnan(outer_skip_rows))
        outer_skip_rows = 0;
    if (isnan(inner_skip_rows))
        inner_skip_rows = 0;

(We shouldn't need that for outer_rows/inner_rows, since the endsel
values can't be 0.)  Messing with clamp_row_est would be a much more
indirect way of fixing it, as well as having more widespread effects.

In the end though, I'm still not terribly excited about this.

            regards, tom lane