PlPgsql buffer+voronoi on lines

gistfile1.sql

drop table if exists zone_buffer;

with
lines as (
	select pid, the_geom the_geom from itineraires
),--end with lines
voronoi as (
	select the_geom
	from (
		select (st_dump(ST_VoronoiPolygons((select st_union(the_geom) from lines)))).geom the_geom
	) tmp
),--end with voronoi
voronoiwithpid as (
	select pid, (case when st_isvalid(the_geom) then the_geom else st_buffer(st_buffer(the_geom,0.001),-0.001) end) the_geom	
	from (
		select l.pid, v.the_geom from voronoi v inner join itineraires l on st_intersects(l.the_geom, v.the_geom) and st_intersects((select st_union(geom) from (select * from st_dumppoints(l.the_geom)) tmp ),v.the_geom)
	) tmp
),--end with voronoiwithpid
buffer as (
	select pid, st_union(the_geom) the_geom
	from (select pid, st_buffer(the_geom, 500) the_geom from lines) tmp
	group by pid
)--end with buffer

select b.pid, st_union(st_intersection(b.the_geom, v.the_geom)) the_geom
into zone_buffer
from buffer b, voronoiwithpid v
where st_intersects(b.the_geom, v.the_geom) and b.pid = v.pid
group by b.pid;

CREATE INDEX zone_buffer_geom_idx
  ON zone_buffer
  USING gist
  (the_geom);

  select Populate_Geometry_Columns((f_table_schema || '.' || f_table_name )::regclass) from geometry_columns where srid=0;