Re: BUG #18990: The results of equivalent queries are inconsistent (one returns 0, another returns -0)

On Thu, Jul 17, 2025 at 5:03 PM PG Bug reporting form
<noreply(at)postgresql(dot)org> wrote:
>
> The following bug has been logged on the website:
>
> Bug reference: 18990
> Logged by: Jinhui
> Email address: jinhui-lai(at)foxmail(dot)com
> PostgreSQL version: 17.5
> Operating system: ubuntu 22.04
> Description:
>
> Hi, PG developers
>
> Thanks for reading my report!
>
> You can reproduce it as follows:
>
> SELECT DISTINCT t1.c0 FROM t1 WHERE NOT EXISTS (SELECT 1 FROM t0 WHERE t1.c0
> > t0.c0)
> UNION
> SELECT DISTINCT t1.c0 FROM t1 WHERE EXISTS (SELECT 1 FROM t0 WHERE t1.c0 >
> t0.c0);
> c0
> ----
> -4
> -3
> -2
> -1
> -0
> 1
>
> SELECT DISTINCT t1.c0 FROM t1;
> c0
> ----
> 0
> -2
> -1
> -4
> -3
> 1
>
> Thanks once again for your precious time.

There is no explanation about what the problem is, can you please
explain what problem you see?

--
Regards,
Dilip Kumar
Google