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Re: Timestamp without Timezone and differing client / server tzs

From: Pushker Chaubey <pchaubey(at)vertex(dot)co(dot)in>
To: Ken Johanson <pg-user(at)kensystem(dot)com>
Cc: pgsql-jdbc(at)postgresql(dot)org
Subject: Re: Timestamp without Timezone and differing client / server tzs
Date: 2008-07-09 07:23:05
Message-ID: 48746759.5080507@vertex.co.in (view raw or flat)
Thread:
Lists: pgsql-jdbc

Ken Johanson wrote:
> The servers and their schema (use-of ts w/o tz are not under my 
> control; adding with-timezone would likely break apps that transmit 
> date values with offset already normalized).
Just wondering, other apps using same database must also be facing the 
same problem as you are if they operate across various timezones.
Since all the applications are sharing the same timestamp(without TZ) 
column they all should follow the same protocol to update and read 
values for this shared timestamp(without TZ) column.

We had a similar situation where the schema (having a timestamp without 
timezone column ) was not under our control and we had clients across 
various timezone who accessed the database.
If one client with timezone TZ1 updated the value, the other client with 
timezone TZ2 did not read the correct value.
To get around that we agreed on a reference timezone (GMT) so that 
stored timestamp value would be as per GMT timezone.
While updating the timestamp values first we had to manipulate it to a 
value as it would be on a jvm with GMT timezone. And after reading it 
from any client on any timezone we were doing the reverse manupulation. 
Since we knew that read timestamp value is as per GMT time zone, we 
could manipulate it to as per clients' time zone.
And this protocol was followed by all the client applications.

But whenever I have control over schema I prefer storing LONG values 
directly (dates converted to millis) to using any database specific 
timestamp implementation. This keeps my code easily adaptable to various 
databases as I do not depend on Database behavior for dealing with 
timestamp objects.

Regards,
Pushker Chaubey



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