From: Tom Lane <tgl@sss.pgh.pa.us>
To: =?UTF-8?B?55SE5piO5rSL?= <zhenmingyang@yeah.net>
cc: pgsql-bugs@postgresql.org
Subject: Re: setting the timezone parameter with space cause diff result
In-reply-to: <37c04704.1327.179eab261fd.Coremail.zhenmingyang@yeah.net>
References: <37c04704.1327.179eab261fd.Coremail.zhenmingyang@yeah.net>
Comments: In-reply-to =?UTF-8?B?55SE5piO5rSL?= <zhenmingyang@yeah.net>
	message dated "Tue, 08 Jun 2021 16:17:09 +0800"
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Date: Tue, 08 Jun 2021 14:02:50 -0400
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=?UTF-8?B?55SE5piO5rSL?= <zhenmingyang@yeah.net> writes:
> /* timezone string with space */
> postgres=# set timezone=' +04:00 ';
> SET
> postgres=# select now();
>               now              
> -------------------------------
>  2021-06-08 05:14:36.486693-03
> (1 row)

What is happening here is that the setting is being interpreted
much like 'X+04:00Y'.  That is, it's taken as a POSIX timezone
specifier with standard-time abbreviation being ' ', daylight-
savings abbreviation also being ' ', and the daylight-savings
offset and transition rules all being defaulted.  Your example
without any spaces is recognized as a POSIX timezone spec
with no DST part, so that's why it behaves differently.

There's certainly room to quibble about whether a single space
ought to be considered a valid zone abbreviation.  However,
this behavior comes directly from the IANA tzcode library,
so I'm hesitant to change it.

			regards, tom lane