hi,
Thank you for your reply!
I’m wondering—since the parameter has already been specified as float8 in the PREPARE statement, why is it still necessary to convert it to float8 again during EXECUTE?
发件人：Laurenz Albe <laurenz.albe@cybertec.at> 发件时间：2025年7月3日 20:23 收件人：798604270 <798604270@qq.com>, pgsql-bugs <pgsql-bugs@lists.postgresql.org> 主题：Re: BUG #18976: -0.0 with float8 will be transformed to 0 inprepare statement but not in normal execution |
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?
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t
(1 row)
Yours,
Laurenz Albe
