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

On 11/1/2024 16:08, Richard Guo wrote:
>
> On Thu, Dec 28, 2023 at 12:30 PM Andrei Lepikhov
> <a(dot)lepikhov(at)postgrespro(dot)ru <mailto: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.
I like it, thanks for your efforts.

--
regards,
Andrei Lepikhov
Postgres Professional