others (#15) - I have error source column contains a null value (#380) - Message List

Hi,

i trying to do a

(SELECT

the_geom

FROM

road, (SELECT

*

FROM

shortest_path_astar('SELECT gid AS id, source::int4, target::int4, cost::double precision, reverse_cost::double precision AS reverse_cost, x1, y1, x2, y2 FROM road', 1524,2979,false,true)) as rt

WHERE

road.gid=rt.edge_id

)

but postgresql8.4.4 return error:

ERROR: source contains a null value

********** Error **********

ERROR: source contains a null value SQL state: XX000

Why?

Help,