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Re: Timestamp with libpq

From: "Wilhansen Li" <willi(dot)t1(at)gmail(dot)com>
To: pgsql-interfaces(at)postgresql(dot)org
Subject: Re: Timestamp with libpq
Date: 2008-10-13 09:32:30
Message-ID: bc9549a50810130232nf40bfd2l2aee3c8c3ff5ec7e@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-interfaces
Actually, I've done this before. And, uh, you can check out my blog for
details:

http://blogs.crammerz-inc.net/thunk/2007/05/09/grabbing_time_in_postgresql_using_libpq
On Mon, Oct 13, 2008 at 3:53 PM, Jakob Lechner <jakob(dot)lechner(at)applstrudl(dot)com
> wrote:

> 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
>
>
> --
> 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
> Web: http://www.applstrudl.com
> Handelsgericht Linz, FN 303988 t
>
> --
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