Subject: Timestamp with libpq
From: Jakob Lechner <jakob.lechner@applstrudl.com>
Reply-To: jakob.lechner@applstrudl.com
To: pgsql-interfaces@postgresql.org
Content-Type: text/plain;
	charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Organization: appl.strudl Software GmbH
Date: Mon, 13 Oct 2008 09:53:01 +0200
Message-Id: <1223884381.3502.10.camel@vie063.fabagl.fabasoft.com>
Mime-Version: 1.0

Hello everybody,

I'm trying to convert timestamp values returned by an SQL query into an
unix time_t. I'm using the libpq library.

For executing the query I use "PQexecParams" with the parameter
"resultFormat" set to 1 in order to obtain results in binary format.

The table I'm fetching data from was created with the following
statement:
create table testtable (c timestamp);

The statement executed by "PQexecParams" is a simple "select"-statement:
select * from testtable;


I've read that postgres internally handles timestamps as double numbers,
where the timestamp is represented in seconds since 2000-01-01.
Thus, I assumed the data returned by "PQgetvalue" for the timestamp
field is encoded in this format. Then I wrote a little routine, which
takes the double number obtained from "PQgetvalue" and converts it into
an unix time_t. This works perfectly if the postgres server (version
8.1.4-1.1) runs on RHEL but if I query the data from a postgres server
(version 8.1.4-1.3) runnning on SLES the result totally wrong.

Any ideas?

Best regards
Jakob Lechner


--=20
Jakob Lechner
Research & Development
appl.strudl Software GmbH
Honauerstra=C3=9Fe 4
A-4020 Linz
Tel.: [+43] (70) 60 61 62
Fax: [+43] (70) 60 61 62-609
E-Mail: jakob.lechner@applstrudl.com
Web: http://www.applstrudl.com
Handelsgericht Linz, FN 303988 t