function compute_posizioni($values_ar, $field_name)
{
    $cnt = 0;
    $msg = sprintf("computing %s\n", $field_name);
    echo pakeColor::colorize($msg, array('fg' => 'cyan', 'bold' => true));
    foreach ($values_ar as $record_id => $value) {
        $cnt++;
        $cached_record = OppPoliticianHistoryCachePeer::retrieveByPK($record_id);
        call_user_func_array(array($cached_record, "set" . ucfirst($field_name) . "Pos"), array($cnt));
        $cached_record->save();
    }
}