Re: Assertion failure with LEFT JOINs among >500 relations

On Fri, 9 Oct 2020 at 12:16, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> > Perhaps the right fix is to modify clamp_row_est() with:
>
> I thought of that too, but as you say, if the rowcount has overflowed a
> double then we've got way worse problems.  It'd make more sense to try
> to keep the count to a saner value in the first place.

I wonder if there was something more logical we could do to maintain
sane estimates too, but someone could surely still cause it to blow up
by writing a long series of clause-less joins. We can't really get
away from the fact that we must estimate those as inner_rows *
outer_rows

I admit it's annoying to add cycles to clamp_row_est() for such insane cases.

David