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

From: PG Bug reporting form <noreply(at)postgresql(dot)org>
To: pgsql-bugs(at)lists(dot)postgresql(dot)org
Cc: jinhui-lai(at)foxmail(dot)com
Subject: BUG #18990: The results of equivalent queries are inconsistent (one returns 0, another returns -0)
Date: 2025-07-17 11:30:40
Message-ID: 18990-a8cecf16fb02d7b0@postgresql.org
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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.

Best regard,

Jinhui

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