create function update_reduced_geom(text, integer)
returns boolean as
'DECLARE tbl ALIAS FOR $1;
create temporary table tempparts as
  select gid, ST_Area((ST_Dump(the_geom)).geom)::bigint as part_area, (ST_Dump(the_geom)).geom
  from tbl;
alter table tempparts add column id serial;
create temporary table tempreduced as
  select gid, ST_Collect(geom) as reduced_geom
  from tempparts t1
  where id in
    (select id from county_parts t2
      where t1.gid = t2.gid order by part_area desc limit $2)
  group by gid;
SELECT AddGeometryColumn (''public'', tbl, ''reduced_geom'', 40000, ''MULTIPOLYGON'',2);
update tbl set reduced_geom =
  (select reduced_geom from county_reduced where tempreduced.gid = tbl.gid);'
language 'sql';