Major breakthrough, just some artifacting to resolve

layers/poi/poi_polygon_update.sql

@@ -1,5 +1,47 @@
--- etldoc:  osm_poi_polygon ->  osm_poi_polygon
-UPDATE osm_poi_polygon  SET geometry=topoint(geometry)
-WHERE ST_GeometryType(geometry) <> 'ST_Point';
+DROP TRIGGER IF EXISTS trigger_flag ON osm_poi_polygon;
+DROP TRIGGER IF EXISTS trigger_refresh ON poi.updates;
 
-ANALYZE osm_poi_polygon;
+-- etldoc:  osm_poi_polygon ->  osm_poi_polygon
+
+CREATE OR REPLACE FUNCTION convert_poi_point() RETURNS VOID AS $$
+BEGIN
+  UPDATE osm_poi_polygon SET geometry=ST_PointOnSurface(geometry) WHERE ST_GeometryType(geometry) <> 'ST_Point';
+  ANALYZE osm_poi_polygon;
+END;
+$$ LANGUAGE plpgsql;
+
+SELECT convert_poi_point();
+
+-- Handle updates
+
+CREATE SCHEMA IF NOT EXISTS poi;
+
+CREATE TABLE IF NOT EXISTS poi.updates(id serial primary key, t text, unique (t));
+CREATE OR REPLACE FUNCTION poi.flag() RETURNS trigger AS $$
+BEGIN
+    INSERT INTO poi.updates(t) VALUES ('y')  ON CONFLICT(t) DO NOTHING;
+    RETURN null;
+END;    
+$$ language plpgsql;
+
+CREATE OR REPLACE FUNCTION poi.refresh() RETURNS trigger AS
+  $BODY$
+  BEGIN
+    RAISE LOG 'Refresh poi';
+    PERFORM convert_poi_point();
+    DELETE FROM poi.updates;
+    RETURN null;
+  END;
+  $BODY$
+language plpgsql;
+
+CREATE TRIGGER trigger_flag
+    AFTER INSERT OR UPDATE OR DELETE ON osm_poi_polygon
+    FOR EACH STATEMENT
+    EXECUTE PROCEDURE poi.flag();
+
+CREATE CONSTRAINT TRIGGER trigger_refresh
+    AFTER INSERT ON poi.updates
+    INITIALLY DEFERRED
+    FOR EACH ROW
+    EXECUTE PROCEDURE poi.refresh();