Message-ID: <501BAE33.4090102@shopzeus.com>
Date: Fri, 03 Aug 2012 12:55:47 +0200
From: Laszlo Nagy <gandalf@shopzeus.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
	rv:14.0) Gecko/20120714 Thunderbird/14.0
MIME-Version: 1.0
To: pgsql-admin@postgresql.org
Subject: Re: Messed up time zones
References: <501B8C6F.6040100@shopzeus.com> <501BAA84.9010306@shopzeus.com>
In-Reply-To: <501BAA84.9010306@shopzeus.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

Here is a better example that shows what I actually have in my database. 
Suppose I have this table, with UTC timestamps in it:

template1=> create table test ( a  timestamptz not null primary key );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index 
"test_pkey" for table "test"
CREATE TABLE
template1=> insert into test values ('2011-10-30 00:00:00'::timestamp at 
time zone 'UTC');
INSERT 0 1
template1=> insert into test values ('2011-10-30 01:00:00'::timestamp at 
time zone 'UTC');
INSERT 0 1
template1=> set datestyle to "postgres, postgres";
SET
template1=> select * from test;
               a
------------------------------
  Sun Oct 30 00:00:00 2011 UTC
  Sun Oct 30 01:00:00 2011 UTC
(2 rows)


I would like to see the same values, just converted into a different 
time zone. But still have timestamptz type!

So I try this:


template1=> select a at time zone 'Europe/Budapest' from test;
          timezone
--------------------------
  Sun Oct 30 02:00:00 2011
  Sun Oct 30 02:00:00 2011
(2 rows)

Which is not good, because the zone information was lost, and so I see 
identical values, but they should be different.

Casting to timestamptz doesn't help either, because casting happens 
after the time zone information was lost:

template1=> select (a at time zone 'Europe/Budapest')::timestamptz from 
test;
            timezone
------------------------------
  Sun Oct 30 02:00:00 2011 UTC
  Sun Oct 30 02:00:00 2011 UTC
(2 rows)

template1=>

So how do I create a query that results in something like:

            a
------------------------------
  Sun Oct 30 02:00:00 2011 +0500
  Sun Oct 30 02:00:00 2011 +0600
(2 rows)