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Re: Messed up time zones

From: Laszlo Nagy <gandalf(at)shopzeus(dot)com>
To: pgsql-admin(at)postgresql(dot)org
Subject: Re: Messed up time zones
Date: 2012-08-03 10:55:47
Message-ID: 501BAE33.4090102@shopzeus.com (view raw or flat)
Thread:
Lists: pgsql-adminpgsql-performance
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)



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