Thread: Postgre connect on Postgre

On Aug 26, 2008, at 7:10 PM, Anderson dos Santos Donda wrote:
> How I can connect a postgre database on another postgre database,
> and manipulate the datas on both database?

There is a module in contrib just for such a purpose:

    http://www.postgresql.org/docs/8.3/interactive/dblink.html

I traced a bug in our application down to this basic operation:

set timezone to 'US/Eastern';

select '11/02/2008'::timestamptz, '12:10'::time,
'11/02/2008'::timestamptz + '12:10'::time;

I have a date and a time stored separately and I want to combine them,
and use them in some timezone-aware calculations.  When I add the time
12:10 to the date 11/2/08, I expect the timestamp "11/2/08 12:10" but
instead, I get "11/2/08 11:10".

It's probably not coincidence that daylight saving time rolls back one hour
on the morning of 11/2.  Still, I would have expected the above behavior
when adding an interval to a timestamp, but not a time.  Is the time being
cast to an interval before the add?  Is there a better way to combine a
date with a time and get a timestamptz ?  (the values are stored in the database, and are not literals as in my
example)

Adam Rich <adam.r@sbcglobal.net> writes:
> I traced a bug in our application down to this basic operation:
> set timezone to 'US/Eastern';

> select '11/02/2008'::timestamptz, '12:10'::time,
> '11/02/2008'::timestamptz + '12:10'::time;

> I have a date and a time stored separately and I want to combine them,
> and use them in some timezone-aware calculations.  When I add the time
> 12:10 to the date 11/2/08, I expect the timestamp "11/2/08 12:10" but
> instead, I get "11/2/08 11:10".

I don't see why that surprises you in the least.
'11/02/2008'::timestamptz means 11/02/2008 00:00 local time, and (given
US DST rules) 11/2/08 11:10 is what the time will be 12 hours and 10
minutes later.

If you want non-DST-aware timekeeping, use timestamp without time zone.

> Still, I would have expected the above behavior
> when adding an interval to a timestamp, but not a time.

How could a time work differently from an interval in this context?

            regards, tom lane

Hi,

Anderson dos Santos Donda wrote:
> Thanks man!!
>
> I'll study this module!!

You should also be aware that sometimes instead of
connecting two separate databases via dblink or similar,
two schemas in one database can be used instead.

It really depends on what you are really doing if
there are even more solutions (like slony for example).

Regards
Tino

PS: the database likes to be called Postgresql or Postgres :-)

> On Tue, Aug 26, 2008 at 11:19 PM, Christophe <xof@thebuild.com
> <mailto:xof@thebuild.com>> wrote:
>
>
>     On Aug 26, 2008, at 7:10 PM, Anderson dos Santos Donda wrote:
>
>         How I can connect a postgre database on another postgre
>         database, and manipulate the datas on both database?
>
>
>     There is a module in contrib just for such a purpose:
>
>            http://www.postgresql.org/docs/8.3/interactive/dblink.html
>
>     --
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