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Message-ID: <fd8e28ef0604270838l52933c36k4d12d4ac4dc1ee5@mail.gmail.com>
Date: Thu, 27 Apr 2006 11:38:25 -0400
From: "Cees Hek" <ceeshek@gmail.com>
To: ichudov@algebra.com
Subject: Re: Apache::Session: can I have a "date" in session
Cc: "Mod_Perl Mailing List" <modperl@perl.apache.org>
In-Reply-To: <20060427152050.GA3339@manifold.algebra.com>
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References: <20060427152050.GA3339@manifold.algebra.com>

On 4/27/06, Igor Chudov <ichudov@algebra.com> wrote:
> I run algebra.com with a few thousand registered users and a lot more
> unregistered. I use Apache::Session to store their session info. Right
> now I clean sessions every month. I would like to be smarter and clean
> sessions based on date information (ie remove sessions that are more
> than 3 weeks old).
>
> Can I have a date as a relational column in the sessions table?
>
> I know that I could maintain a date in the session data blob, but, it
> is expensive to use that for a few reasons.

You can have the database do all that for you using a trigger (if your
database suports it).  I have used PostgreSQL in the past to do the
following:

CREATE TABLE sessions (
   id varchar(32) NOT NULL PRIMARY KEY,
   a_session text NOT NULL,
   lm timestamp with time zone DEFAULT now()
);
CREATE FUNCTION update_session_lm() RETURNS "trigger"
   AS '
   BEGIN
     NEW.lm :=3D ''now'';
     RETURN NEW;
   END;
 '
   LANGUAGE plpgsql;

CREATE TRIGGER update_session_lm_trig
   BEFORE UPDATE ON sessions
   FOR EACH ROW
   EXECUTE PROCEDURE update_session_lm();

The deleting the sessions becomes a simple SQL statement against the
lm column.  And this requires no code changes as everything is handled
in the database.

There is always a trade off though.  This means more load up front
when the sessions are created and/or altered.  The database has to do
slightly more work on each request to make the expiring of sessions
easy for you in the end.

Cheers,

Cees