Major breakthrough, just some artifacting to resolve

layers/water_name/water_point.sql

@@ -1,15 +1,50 @@
-
-DROP TABLE IF EXISTS osm_water_point CASCADE;
+DROP TRIGGER IF EXISTS trigger_flag_point ON osm_water_polygon;
+DROP TRIGGER IF EXISTS trigger_refresh ON water_point.updates;
 
 -- etldoc:  osm_water_polygon ->  osm_water_point
 -- etldoc:  lake_centerline ->  osm_water_point
-CREATE TABLE IF NOT EXISTS osm_water_point AS (
+DROP MATERIALIZED VIEW IF EXISTS  osm_water_point CASCADE;
+
+CREATE MATERIALIZED VIEW osm_water_point AS (
     SELECT
-        wp.osm_id, topoint(wp.geometry) AS geometry,
+        wp.osm_id, ST_PointOnSurface(wp.geometry) AS geometry,
         wp.name, wp.name_en, ST_Area(wp.geometry) AS area
     FROM osm_water_polygon AS wp
     LEFT JOIN lake_centerline ll ON wp.osm_id = ll.osm_id
     WHERE ll.osm_id IS NULL AND wp.name <> ''
 );
-
 CREATE INDEX IF NOT EXISTS osm_water_point_geometry_idx ON osm_water_point USING gist (geometry);
+ 
+-- Handle updates
+
+CREATE SCHEMA IF NOT EXISTS water_point;
+
+CREATE TABLE IF NOT EXISTS water_point.updates(id serial primary key, t text, unique (t));
+CREATE OR REPLACE FUNCTION water_point.flag() RETURNS trigger AS $$
+BEGIN
+    INSERT INTO water_point.updates(t) VALUES ('y')  ON CONFLICT(t) DO NOTHING;
+    RETURN null;
+END;    
+$$ language plpgsql;
+
+CREATE OR REPLACE FUNCTION water_point.refresh() RETURNS trigger AS
+  $BODY$
+  BEGIN
+    RAISE LOG 'Refresh water_point';
+    REFRESH MATERIALIZED VIEW osm_water_point;
+    DELETE FROM water_point.updates;
+    RETURN null;
+  END;
+  $BODY$
+language plpgsql;
+
+CREATE TRIGGER trigger_flag_point
+    AFTER INSERT OR UPDATE OR DELETE ON osm_water_polygon
+    FOR EACH STATEMENT
+    EXECUTE PROCEDURE water_point.flag();
+
+CREATE CONSTRAINT TRIGGER trigger_refresh
+    AFTER INSERT ON water_point.updates
+    INITIALLY DEFERRED
+    FOR EACH ROW
+    EXECUTE PROCEDURE water_point.refresh();