Re: BUG #18260: Unexpected error: "negative bitmapset member not allowed" triggered by multiple JOIN

On Thu, Dec 28, 2023 at 12:30 PM Andrei Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru>
wrote:

> On 28/12/2023 10:03, Richard Guo wrote:
> > if (bms_is_subset(phinfo->ph_needed, joinrelids) &&
> > bms_is_member(relid, phinfo->ph_eval_at) &&
> > - !bms_is_member(ojrelid, phinfo->ph_eval_at))
> > + (sjinfo == NULL || !bms_is_member(ojrelid,
> phinfo->ph_eval_at)))
>
> > Alternatively, we can modify bms_is_member() to return false for
> > negative numbers instead of emitting an error, as suggested by the
> > comment there.
> > - /* XXX better to just return false for x<0 ? */
> > + /* negative number cannot be a member of the bitmapset */
> > if (x < 0)
> > - elog(ERROR, "negative bitmapset member not allowed");
> > + return false;
> >
> > I prefer the second option, but I'm open to other thoughts.
> I don't like this option. It could mask some blunders somewhere like a
> current one.

After a second thought, I agree that the first option is better. It
maintains consistency with the Assert a few lines ahead, and also
minimizes the potential impact of code changes compared to the second
option.

> > FWIW, here is a simplified repro for this error.
> >
> > create table t (a int primary key, b int);
> >
> > explain (verbose, costs off)
> > select 1 from t t1 left join
> > (lateral (select 1 as x, * from t t2) s1 inner join
> > (select * from t t3) s2 on s1.a = s2.a)
> > on true
> > where s1.x = 1;
> > ERROR: negative bitmapset member not allowed
> It can be simplified even more (without LATERAL):

Indeed. I realized this shortly after v1 patch was sent out, and was
thinking that it wasn't worth the effort to update the patch with a new
version just for this issue.

Thanks
Richard