Aggregation of buildings

layers/building/building.sql

@@ -1,3 +1,5 @@
+--\timing on
+
 -- etldoc: layer_building[shape=record fillcolor=lightpink, style="rounded,filled",
 -- etldoc:     label="layer_building | <z13> z13 | <z14_> z14+ " ] ;
 
@@ -75,11 +77,11 @@ CREATE OR REPLACE FUNCTION layer_building(bbox geometry, zoom_level int)
 RETURNS TABLE(geometry geometry, osm_id bigint, render_height int, render_min_height int) AS $$
     SELECT geometry, osm_id, render_height, render_min_height
     FROM (
-        -- etldoc: osm_building_polygon_gen1 -> layer_building:z13
+        -- etldoc: osm_building_block_gen1 -> layer_building:z13
         SELECT
             osm_id, geometry,
             NULL::int AS render_height, NULL::int AS render_min_height
-        FROM osm_building_polygon_gen1
+        FROM osm_building_block_gen1
         WHERE zoom_level = 13 AND geometry && bbox
         UNION ALL
         -- etldoc: osm_building_polygon -> layer_building:z14_

layers/building/building.yaml

@@ -12,6 +12,7 @@ layer:
     render_min_height: |
         An approximated height from levels and height of the bottom of the building or building:part after the method of Paul Norman in [OSM Clear](https://github.com/ClearTables/osm-clear). For future 3D rendering of buildings.
 schema:
+  - ./update_building.sql
   - ./building.sql
 datasources:
   - type: imposm3

layers/building/mapping.yaml

@@ -1,9 +1,9 @@
-generalized_tables:
-  # etldoc: imposm3 -> osm_building_polygon_gen1
-  building_polygon_gen1:
-    source: building_polygon
-    sql_filter: area>power(ZRES12,2) AND ST_IsValid(geometry)
-    tolerance: ZRES14
+#generalized_tables:
+#  # etldoc: imposm3 -> osm_building_polygon_gen1
+#  building_polygon_gen1:
+#    source: building_polygon
+#    sql_filter: area>power(ZRES12,2) AND ST_IsValid(geometry)
+#    tolerance: ZRES14
 
 tables:
   # etldoc: imposm3 -> osm_building_polygon

layers/building/update_building.sql

@@ -0,0 +1,136 @@
+DROP TRIGGER IF EXISTS trigger_refresh ON buildings.updates;
+DROP TRIGGER IF EXISTS trigger_flag ON osm_building_polygon;
+
+--creating aggregated building blocks with removed small polzgons and small
+--holes. Aggregated polzgons are simplified.
+
+--function returning recordset for matview
+--returning recordset of buildings aggregates by zres 14, with removed small
+--holes and with removed small buildings/blocks
+--
+
+CREATE OR REPLACE FUNCTION osm_building_block_gen1( )
+RETURNS table(
+   osm_id bigint
+   , geometry geometry
+)
+LANGUAGE plpgsql
+VOLATILE
+ -- common options:  IMMUTABLE  STABLE  STRICT  SECURITY DEFINER
+AS $function$
+DECLARE
+zres14 float := Zres(14);
+zres12 float := Zres(12);
+BEGIN
+   FOR osm_id, geometry IN
+      WITH dta AS ( --CTE is used because of optimalization 
+	 SELECT o.osm_id, o.geometry
+	 , ST_ClusterDBSCAN(o.geometry, eps := zres14, minpoints := 1) over() cid
+	 FROM osm_building_polygon o
+      ) 
+      SELECT 
+      (array_agg(dta.osm_id))[1]
+      , ST_Buffer(
+	 ST_MemUnion(
+	    ST_Buffer(
+	       dta.geometry
+	       , zres14
+	       , 'join=mitre'
+	    )
+	 )
+	 , -zres14
+	 , 'join=mitre'
+      ) geometry
+      FROM dta
+      GROUP BY cid
+      LOOP
+	 --removing holes smaller than
+	 IF ST_NumInteriorRings(geometry) > 0 THEN--only from geometries wih holes
+	    geometry := (
+	       SELECT ST_Collect( --there are some multigeometries in this layer
+		  gn
+	       )
+	       FROM (
+		  SELECT
+		  COALESCE( --in some cases are "holes" NULL, because all holes are smaller than
+		     ST_MakePolygon(
+			ST_ExteriorRing(dmp.geom) --exterior ring
+			, holes 
+		     )
+		     , 
+		     ST_MakePolygon(
+			ST_ExteriorRing(dmp.geom)
+		     )
+		  ) gn
+		  FROM
+		  ST_Dump(geometry) dmp --1 dump polygons
+		  , LATERAL (
+		     SELECT
+		     ST_Accum(
+			ST_Boundary(rg.geom) --2 create array
+		     ) holes
+		     FROM
+		     ST_DumpRings(dmp.geom) rg --3 from rings
+		     WHERE rg.path[1] > 0 --5 except inner ring
+		     AND ST_Area(rg.geom) >= power(zres12,2) --4 bigger than
+		  ) holes
+	       ) new_geom
+	    );
+	 END IF;
+
+	 IF ST_Area(geometry) < power(zres12,2) THEN
+	    CONTINUE;
+	 END IF;
+
+	 --simplify
+	 geometry := ST_SimplifyPreserveTopology(geometry, zres14::float);
+
+	 RETURN NEXT;
+      END LOOP;
+END;
+
+$function$;
+
+DROP MATERIALIZED VIEW IF EXISTS osm_building_block_gen1; --drop table, if exists
+
+
+CREATE MATERIALIZED VIEW osm_building_block_gen1 AS
+SELECT * FROM osm_building_block_gen1();
+
+CREATE INDEX on osm_building_block_gen1 USING gist(geometry);
+CREATE UNIQUE INDEX on osm_building_block_gen1 USING btree(osm_id);
+
+
+-- Handle updates
+
+CREATE SCHEMA IF NOT EXISTS buildings;
+
+CREATE TABLE IF NOT EXISTS buildings.updates(id serial primary key, t text, unique (t));
+CREATE OR REPLACE FUNCTION buildings.flag() RETURNS trigger AS $$
+BEGIN
+    INSERT INTO buildings.updates(t) VALUES ('y')  ON CONFLICT(t) DO NOTHING;
+    RETURN null;
+END;
+$$ language plpgsql;
+
+CREATE OR REPLACE FUNCTION buildings.refresh() RETURNS trigger AS
+  $BODY$
+  BEGIN
+    RAISE LOG 'Refresh buildings block';
+    REFRESH MATERIALIZED VIEW osm_building_block_gen1;
+    DELETE FROM buildings.updates;
+    RETURN null;
+  END;
+  $BODY$
+language plpgsql;
+
+CREATE TRIGGER trigger_flag
+    AFTER INSERT OR UPDATE OR DELETE ON osm_building_polygon
+    FOR EACH STATEMENT
+    EXECUTE PROCEDURE buildings.flag();
+
+CREATE CONSTRAINT TRIGGER trigger_refresh
+    AFTER INSERT ON buildings.updates
+    INITIALLY DEFERRED
+    FOR EACH ROW
+    EXECUTE PROCEDURE buildings.refresh();