clear select

would this not clear the whole query though rather than just the select element ?

PHP Code:

<?php
// Not tested but i would go for something like this
$select = ( null !== $rs_type && 'small_select' == $rs_type ) ? 'user.user_id' : 'user.*';
$query  = $this->db->select($select)->get('users');

$result = $query->result();