From: Laurenz Albe <laurenz.albe@cybertec.at>
To: 798604270@qq.com
To: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18976: -0.0 with float8 will be transformed to 0 in prepare statement but not in normal execution
Date: Thu, 03 Jul 2025 14:23:42 +0200
Message-ID: <c8c5090a0d720db8a5c4c382cce59afde3dc65d2.camel@cybertec.at> (raw)
In-Reply-To: <18976-c1bc92542b90e5e6@postgresql.org>
References: <18976-c1bc92542b90e5e6@postgresql.org>
On Thu, 2025-07-03 at 03:03 +0000, PG Bug reporting form wrote:
> The following bug has been logged on the website:
>
> Bug reference: 18976
> Logged by: Chi Zhang
> Email address: 798604270@qq.com
> PostgreSQL version: 18beta1
> Operating system: Ubuntu 24.04 and docker
> Description:
>
> The value -0.0 with float8 is transformed to 0 in prepared statements but
> remains -0 in normal execution. Although 0 and -0 are numerically equal,
> this discrepancy can lead to subtle bugs in certain cases—for example, when
> the value is cast to a VARCHAR, as illustrated below.
>
> PREPARE prepare_query (float8) AS SELECT CAST($1 AS VARCHAR) =
> CAST(-0.0::float8 AS VARCHAR);
> EXECUTE prepare_query(-0.0); -- f
That's not a bug, but a pilot error. If you feed a "float8", the result ist TRUE:
EXECUTE prepare_query(-0.0::float8);
?column?
══════════
t
(1 row)
Yours,
Laurenz Albe
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To: pgsql-bugs@postgresql.org
Cc: laurenz.albe@cybertec.at, 798604270@qq.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18976: -0.0 with float8 will be transformed to 0 in prepare statement but not in normal execution
In-Reply-To: <c8c5090a0d720db8a5c4c382cce59afde3dc65d2.camel@cybertec.at>
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