ST_CarvesPolygons

DROP FUNCTION IF EXISTS ST_CarvesPolygons(
geom1 GEOMETRY, 
geom2 GEOMETRY)

CREATE OR REPLACE FUNCTION ST_CarvesPolygons(
geom1 GEOMETRY, 
geom2 GEOMETRY)
RETURNS TABLE (geom GEOMETRY) AS
$BODY$
      WITH
          in_gd1 AS (SELECT ($1) geom),
          in_gd2 AS (SELECT ($2) geom)
          SELECT (ST_Dump(ST_Difference(a.geom, b.geom))).geom geom FROM in_gd2 a CROSS JOIN LATERAL (SELECT ST_Collect(geom) AS geom FROM in_gd1 WHERE ST_Intersects(a.geom, geom)) AS b;   
$BODY$
LANGUAGE SQL

SELECT ST_CarvesPolygons(a.geom, b.geom) geom FROM (SELECT ST_Collect(geom) geom FROM polygons) a, poly_extent b;