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@postgresql.org> wrote:
>
> The following bug has been logged on the website:
>
> Bug reference:      18990
> Logged by:          Jinhui
> Email address:      jinhui-lai@foxmail.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