+
+CREATE OR REPLACE FUNCTION quad_split_geometry(geometry GEOMETRY, maxarea FLOAT, maxdepth INTEGER)
+ RETURNS SETOF GEOMETRY
+ AS $$
+DECLARE
+ xmin FLOAT;
+ ymin FLOAT;
+ xmax FLOAT;
+ ymax FLOAT;
+ xmid FLOAT;
+ ymid FLOAT;
+ secgeo GEOMETRY;
+ secbox GEOMETRY;
+ seg INTEGER;
+ geo RECORD;
+ area FLOAT;
+ remainingdepth INTEGER;
+ added INTEGER;
+
+BEGIN
+
+-- RAISE WARNING 'quad_split_geometry: maxarea=%, depth=%',maxarea,maxdepth;
+
+ IF (ST_GeometryType(geometry) not in ('ST_Polygon','ST_MultiPolygon') OR NOT ST_IsValid(geometry)) THEN
+ RETURN NEXT geometry;
+ RETURN;
+ END IF;
+
+ remainingdepth := maxdepth - 1;
+ area := ST_AREA(geometry);
+ IF remainingdepth < 1 OR area < maxarea THEN
+ RETURN NEXT geometry;
+ RETURN;
+ END IF;
+
+ xmin := st_xmin(geometry);
+ xmax := st_xmax(geometry);
+ ymin := st_ymin(geometry);
+ ymax := st_ymax(geometry);
+ secbox := ST_SetSRID(ST_MakeBox2D(ST_Point(ymin,xmin),ST_Point(ymax,xmax)),4326);
+
+ -- if the geometry completely covers the box don't bother to slice any more
+ IF ST_AREA(secbox) = area THEN
+ RETURN NEXT geometry;
+ RETURN;
+ END IF;
+
+ xmid := (xmin+xmax)/2;
+ ymid := (ymin+ymax)/2;
+
+ added := 0;
+ FOR seg IN 1..4 LOOP
+
+ IF seg = 1 THEN
+ secbox := ST_SetSRID(ST_MakeBox2D(ST_Point(xmin,ymin),ST_Point(xmid,ymid)),4326);
+ END IF;
+ IF seg = 2 THEN
+ secbox := ST_SetSRID(ST_MakeBox2D(ST_Point(xmin,ymid),ST_Point(xmid,ymax)),4326);
+ END IF;
+ IF seg = 3 THEN
+ secbox := ST_SetSRID(ST_MakeBox2D(ST_Point(xmid,ymin),ST_Point(xmax,ymid)),4326);
+ END IF;
+ IF seg = 4 THEN
+ secbox := ST_SetSRID(ST_MakeBox2D(ST_Point(xmid,ymid),ST_Point(xmax,ymax)),4326);
+ END IF;
+
+ IF st_intersects(geometry, secbox) THEN
+ secgeo := st_intersection(geometry, secbox);
+ IF NOT ST_IsEmpty(secgeo) AND ST_GeometryType(secgeo) in ('ST_Polygon','ST_MultiPolygon') THEN
+ FOR geo IN select quad_split_geometry(secgeo, maxarea, remainingdepth) as geom LOOP
+ IF NOT ST_IsEmpty(geo.geom) AND ST_GeometryType(geo.geom) in ('ST_Polygon','ST_MultiPolygon') THEN
+ added := added + 1;
+ RETURN NEXT geo.geom;
+ END IF;
+ END LOOP;
+ END IF;
+ END IF;
+ END LOOP;
+
+ RETURN;
+END;
+$$
+LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION split_geometry(geometry GEOMETRY)
+ RETURNS SETOF GEOMETRY
+ AS $$
+DECLARE
+ geo RECORD;
+BEGIN
+ -- 10000000000 is ~~ 1x1 degree
+ FOR geo IN select quad_split_geometry(geometry, 0.25, 20) as geom LOOP
+ RETURN NEXT geo.geom;
+ END LOOP;
+ RETURN;
+END;
+$$
+LANGUAGE plpgsql;