Steve Crawford wrote:
On 06/14/2011 05:13 AM, Mark Morgan Lloyd wrote:
Karsten Hilbert wrote:
On Tue, Jun 14, 2011 at 09:40:20AM +0000, Mark Morgan Lloyd wrote:
Is it possible to incorporate SET TIMEZONE into a query, so that
to_char(...'TZ') etc. is appropriately localised?
You seem to want "AT TIME ZONE".
Thanks for that. How can I do /this/
select to_char(now() at time zone 'GMT0BST', 'TZ');
It appears to return '', while if I used a separate SET TIMEZONE I'd
expect 'BST'.
The "now()" function returns a timestamp with time zone (aka a point in
time). When you ask for a timestamp with time zone at a specific time
zone, you get a timestamp *without* time zone (you provided and
therefore know the desired time zone and PostgreSQL returned the
timestamp in that zone).
I'm a bit concerned with your initial statement that "The development
environment I'm working with uses short-lifetime sessions, and it's
proving difficult to get a set command and a query associated with the
same handle.". Do I take this to mean that connections are going through
some sort of pooler that is allocating connections on as short as a
per-statement basis so you might end up with a different connection
between the "set time zone.." statement and the query? If so, you may
start to find all sorts of other issues.
It's a bit convoluted, but you could get the zone from a subquery and
select the timestamp converted to that zone along with the zone itself
from the outer query:
select now() at time zone foo.tz, foo.tz from (select 'est5edt'::text as
tz) as foo;
Looking back through the mailing list, the issue appears to be the way
that AT TIME ZONE is parsed into a function which returns a string. I
think the easiest way round most of this is going to be to use the PGTZ
shell variable, otherwise I think I can pull the info I need out of
pg_timezone_names subject to using the correct zone name.
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
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