1. It depends.

2. You can either edit CGI::Session::MySQL or edit your own (I called mine CGI::Session::MySQLtheSequel...no pun intended). You will need the following table created in your database:

CREATE TABLE sessions (
        id CHAR(32) NOT NULL UNIQUE,
        a_session TEXT NOT NULL,
        expires int unsigned NOT NULL
    );
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You will also need to alter the store sub in your package.

sub store {
    my ($self, $sid, $options, $data) = @_;   

    my $dbh = $self->MySQL_dbh($options);
    my $lck_status = $dbh->selectrow_array(qq|SELECT GET_LOCK("$sid", 
+10)|);
    unless ( $lck_status == 1 ) {
        $self->error("Couldn't acquire lock on id '$sid'. Lock status:
+ $lck_status");
        return undef;
    }

    $dbh->do(qq|REPLACE INTO $TABLE_NAME (id, a_session, expires) VALU
+ES(?,?,?)|, undef, $sid, $self->freeze($data),$self->expire() + $self
+->atime());
    
    return $dbh->selectrow_array(qq|SELECT RELEASE_LOCK("$sid")|);
}
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Now in your code for clearing out the expired session id's, run this do:

$dbh->do("delete from sessions where expires<?",undef,time());
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Just be certain to set $session->expire() to something or it will never get deleted. Hope this helps.

antirice    
The first rule of Perl club is - use Perl
The ith rule of Perl club is - follow rule i - 1 for i > 1

2. I haven't used CGI::Session yet so someone may have CGI::Session specific advice. However what I would do is give each row in my table a date field that holds the expiration date for the session. Then in a cron job, run a script that deletes all rows that have expired session dates.

1. 1 - 5 million total users.

2. I was wondering if there was a built in feature in CGI::Session that removes the row, after the expiration date had expire.

Could you be a little more specific as to what "1 - 5 million people" means?

I assume that you are using mod_perl as the backend, and mod_perl can certainly handle that type of load (see mod_perl Success Stories if you don't believe me). However, without more details about your site, it is hard to say for sure.