Microcosm Feature Suggestions

I need a scratchpad... this will do:

SELECT (line / 50000) + 1 AS sitemap_file
      ,line
      ,item_type_id
      ,item_id
  FROM (
           SELECT row_number() OVER() AS line
                 ,item_type_id
                 ,item_id
             FROM flags
            WHERE site_id = 234
              AND item_type_id != 5
              AND parent_item_type_id NOT IN (3, 5)
            ORDER BY last_modified ASC
       ) AS f
 ORDER BY line ASC
 LIMIT 50