SQL for building a dynamic topo

gistfile1.sql

WITH 
	setup AS (
		SELECT 
                   ST_Transform(ST_Buffer(the_geom::geography,n*100)::geometry,3857) the_geom_webmercator, 
                   (cars*(10.0 - n)/10.0) as cars 
                FROM troparevo_nikulino_1, generate_series(1,9) n
	),
	maxcars AS (
		SELECT max(cars)::float as mostcars FROM setup
	)
(SELECT 
   ST_Buffer(ST_Buffer(ST_Union(the_geom_webmercator),400),-400) AS the_geom_webmercator, 
   round((2*cars/mostcars)::numeric,1)/2 cars, 
   'topo' as layer 
FROM setup,maxcars 
GROUP BY round((2*cars/mostcars)::numeric,1)/2 
ORDER BY round((2*cars/mostcars)::numeric,1)/2 DESC)
UNION ALL
SELECT 
   the_geom_webmercator, 
   round((cars/mostcars)::numeric,1) as cars, 
   'points' as layer 
FROM troparevo_nikulino_1, maxcars