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Timestamp with libpq

From: Jakob Lechner <jakob(dot)lechner(at)applstrudl(dot)com>
To: pgsql-interfaces(at)postgresql(dot)org
Subject: Timestamp with libpq
Date: 2008-10-13 07:53:01
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-interfaces
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
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

Jakob Lechner
Research & Development
appl.strudl Software GmbH
Honauerstra├če 4
A-4020 Linz
Tel.: [+43] (70) 60 61 62
Fax: [+43] (70) 60 61 62-609
E-Mail: jakob(dot)lechner(at)applstrudl(dot)com
Handelsgericht Linz, FN 303988 t


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Subject: Re: Timestamp with libpq
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