From: myzhen <zhenmingyang@yeah.net>
To: pgsql-bugs@postgresql.org
Subject: to_timestamp function calculation error
Date: Tue, 17 Dec 2024 19:51:44 +0800 (CST)
Message-ID: <4833ac30.18d0.193d475b6d3.Coremail.zhenmingyang@yeah.net> (raw)
When calling the to_timestamp function, if the actual parameter passed is a negative year and you specify BC, this will cause to_timestamp to return an AD date.
example：select to_timestamp('-2011-2-18 15:13:14 BC', 'YYYY-MM-DD HH24:MI:SS BC');
I tested is as follows:
postgres=# select to_timestamp('-2011-2-18 15:13:14', 'YYYY-MM-DD HH24:MI:SS BC');
to_timestamp
---------------------------------
2011-02-18 15:13:14+08:05:43 BC
(1 row)
postgres=# select to_timestamp('-2011-2-18 15:13:14 BC', 'YYYY-MM-DD HH24:MI:SS BC');
to_timestamp
------------------------
2011-02-18 15:13:14+08
(1 row)
postgres=# select to_timestamp('-2011-2-18 15:13:14 BC', 'YYYY-MM-DD HH24:MI:SS BC') = to_timestamp('2011-2-18 15:13:14', 'YYYY-MM-DD HH24:MI:SS');
?column?
----------
t
(1 row)
postgres=#
I found the following code snippet in do_to_timestamp function:
{
/* If a 4-digit year is provided, we use that and ignore CC. */
tm->tm_year = tmfc.year;
if (tmfc.bc)
tm->tm_year = -tm->tm_year;
/* correct for our representation of BC years */
if (tm->tm_year < 0)
tm->tm_year++;
}
As long as tmfc.bc is true, tm->tm_year = tm->tm_year * -1, that's what led to this scene.
I haven't tested on other DBMS so I'm not sure if that's an issue.
Best regards
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-bugs@postgresql.org
Cc: zhenmingyang@yeah.net
Subject: Re: to_timestamp function calculation error
In-Reply-To: <4833ac30.18d0.193d475b6d3.Coremail.zhenmingyang@yeah.net>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox