How to create infrastructure coverage using pgRouting?

Question

I'm trying to reproduce what Underdark did here.
I succesfully installed pgrouting and the two required function (nearest neighbour and driving_distance).
cdv_osm_v contains all the openstreetmap points of my region, from which I select only transportation infrastructure.
taa_2po_4pgr and taa_2po_v contain network and nodes extracted by osm2po for my region.
When I try to run this query in pgAdmin3 I got a syntax error at or near "FOR".
The first select works well, and also driving_distance outputs results fine if called separately.
I'm a noob at postgresql/postgis and I don't know how to pass a geometry to nn() to test it separately (and maybe x,y and factor parameters are not so good).
What am I doing wrong?

CREATE TEMPORARY TABLE nodes_costs (vertex_id integer,edge_id integer,cost double precision);

FOR i IN
  SELECT the_geom
  FROM cdv_osm_v
  WHERE highway like 'bus_stop' OR railway like 'station' or amenity like 'bus_station'
LOOP
  INSERT INTO nodes_cost
  driving_distance(
    'SELECT id, source, target, km AS cost
    FROM taa_2po_4pgr',
    mm(i.the_geom ,0.0001,2,2,'taa_2po_v','id','geom_vertex'), 0.4, false, false);
END LOOP;

SELECT * 
FROM taa_2po_v 
JOIN 
  SELECT vertex_id, min(cost) AS costo
  FROM nodes_costs
ON
taa_2po_v.id = nodes_costs.vertex_id;

I forgot: posgresql 9.1, postgis 2.0.1, pgrouting 1.0.5 from kyngchaos.

Answer 1

Ok, I got it!
First thing first, in PostgreSQL I cannot execute inline commands, so I had to write a function.
Then, driving_distance returns a SETOF (namely, a table), so I had to loop through this set and insert the records in my table. I don't know if it could be rewritten in a more efficient way.
Finally, a correction to the output query to make all three fields available.
Here's the result:

CREATE OR REPLACE FUNCTION coverage() RETURNS TABLE(geometria geometry, id_vertice integer, costo_tot double precision) AS $$
DECLARE
  i RECORD;
  dd_record RECORD;
BEGIN
CREATE TEMPORARY TABLE nodes_costs (vertex_id integer,edge_id integer,cost double precision) ON COMMIT DROP;

FOR i IN
  SELECT the_geom FROM cdv_osm_v  WHERE highway like 'bus_stop' OR railway like 'station' or amenity like 'bus_station'
 LOOP
  FOR dd_record IN SELECT * from driving_distance('SELECT id, source, target, km AS cost FROM taa_2po_4pgr', nn(i.the_geom ,0.0001,2,2,'taa_2po_v','id','geom_vertex'), 1, false, false)
  LOOP
     INSERT INTO nodes_costs VALUES ( dd_record.vertex_id,dd_record.edge_id,dd_record.cost);
  END LOOP;
 END LOOP;
 RETURN QUERY SELECT geom_vertex, vertex_id, costo
 FROM taa_2po_v 
 JOIN 
   (SELECT vertex_id, min(cost) AS costo
   FROM nodes_costs GROUP BY vertex_id) AS costs_nodes
 ON
 taa_2po_v.id = costs_nodes.vertex_id;
 END;
$$ LANGUAGE plpgsql;

SELECT * FROM coverage();