Make more simple incremental update (#944)

Replacing update on the whole table with an update only on changed rows.

The goal is to update more quickly by just updating the changing content.
The update now focus on osm_id of changed rows, it use index. Add a where clause tags != update_tags(tags, geometry) en ensure only update when changed.

It requires one more trigger and a table to store changed osm_id.

The UPDATE is keep in a function to be reusable for initial setup and trigger update.

I try many code layout before done it in this way with the goal to keep the code for initial pass and for update. It should have low impact on initial data load. Better performance for row update can be achieve with BEFORE UPDATE, but require to duplicate the logic.

It is not based on the already merged https://github.com/openmaptiles/openmaptiles/pull/896 because calling and update within a function for each updated row was not efficient for larger table (like housenumber).

It addresses #814.


* Remake update_peak_point use incremental update #814

* Make update_aerodrome_label_point use incremental update #814

* Make housenumber_centroid use incremental update #814

* Make update_continent_point use incremental update #814

* Make update_island_point use incremental update #814

* Make update_island_polygon use incremental update #814

* Remove dead code in update_state_point.sql

* Make update_state_point use incremental update #814

* Remove dead code in update_country_point.sql

* Make update_country_point use incremental update #814

* Make osm_poi_polygon use incremental update #814

Thanks @frodrigo

layers/poi/update_poi_polygon.sql

@@ -1,11 +1,18 @@
 DROP TRIGGER IF EXISTS trigger_flag ON osm_poi_polygon;
+DROP TRIGGER IF EXISTS trigger_store ON osm_poi_polygon;
 DROP TRIGGER IF EXISTS trigger_refresh ON poi_polygon.updates;
 
+CREATE SCHEMA IF NOT EXISTS poi_polygon;
+
+CREATE TABLE IF NOT EXISTS poi_polygon.osm_ids
+(
+    osm_id bigint
+);
+
 -- etldoc:  osm_poi_polygon ->  osm_poi_polygon
 
-CREATE OR REPLACE FUNCTION update_poi_polygon() RETURNS void AS
+CREATE OR REPLACE FUNCTION update_poi_polygon(full_update boolean) RETURNS void AS
 $$
-BEGIN
     UPDATE osm_poi_polygon
     SET geometry =
             CASE
@@ -13,31 +20,44 @@ BEGIN
                     THEN ST_Centroid(geometry)
                 ELSE ST_PointOnSurface(geometry)
                 END
-    WHERE ST_GeometryType(geometry) <> 'ST_Point';
+    WHERE (full_update OR osm_id IN (SELECT osm_id FROM poi_polygon.osm_ids))
+      AND ST_GeometryType(geometry) <> 'ST_Point';
 
     UPDATE osm_poi_polygon
     SET subclass = 'subway'
-    WHERE station = 'subway'
+    WHERE (full_update OR osm_id IN (SELECT osm_id FROM poi_polygon.osm_ids))
+      AND station = 'subway'
       AND subclass = 'station';
 
     UPDATE osm_poi_polygon
     SET subclass = 'halt'
-    WHERE funicular = 'yes'
+    WHERE (full_update OR osm_id IN (SELECT osm_id FROM poi_polygon.osm_ids))
+      AND funicular = 'yes'
       AND subclass = 'station';
 
     UPDATE osm_poi_polygon
     SET tags = update_tags(tags, geometry)
-    WHERE COALESCE(tags->'name:latin', tags->'name:nonlatin', tags->'name_int') IS NULL;
+    WHERE (full_update OR osm_id IN (SELECT osm_id FROM poi_polygon.osm_ids))
+      AND COALESCE(tags->'name:latin', tags->'name:nonlatin', tags->'name_int') IS NULL
+      AND tags != update_tags(tags, geometry);
 
-    ANALYZE osm_poi_polygon;
-END;
-$$ LANGUAGE plpgsql;
+$$ LANGUAGE SQL;
 
-SELECT update_poi_polygon();
+SELECT update_poi_polygon(true);
 
 -- Handle updates
 
-CREATE SCHEMA IF NOT EXISTS poi_polygon;
+CREATE OR REPLACE FUNCTION poi_polygon.store() RETURNS trigger AS
+$$
+BEGIN
+    IF (tg_op = 'DELETE') THEN
+        INSERT INTO poi_polygon.osm_ids VALUES (OLD.osm_id);
+    ELSE
+        INSERT INTO poi_polygon.osm_ids VALUES (NEW.osm_id);
+    END IF;
+    RETURN NULL;
+END;
+$$ LANGUAGE plpgsql;
 
 CREATE TABLE IF NOT EXISTS poi_polygon.updates
 (
@@ -57,13 +77,21 @@ CREATE OR REPLACE FUNCTION poi_polygon.refresh() RETURNS trigger AS
 $$
 BEGIN
     RAISE LOG 'Refresh poi_polygon';
-    PERFORM update_poi_polygon();
+    PERFORM update_poi_polygon(false);
+    -- noinspection SqlWithoutWhere
+    DELETE FROM poi_polygon.osm_ids;
     -- noinspection SqlWithoutWhere
     DELETE FROM poi_polygon.updates;
     RETURN NULL;
 END;
 $$ LANGUAGE plpgsql;
 
+CREATE TRIGGER trigger_store
+    AFTER INSERT OR UPDATE OR DELETE
+    ON osm_poi_polygon
+    FOR EACH ROW
+EXECUTE PROCEDURE poi_polygon.store();
+
 CREATE TRIGGER trigger_flag
     AFTER INSERT OR UPDATE OR DELETE
     ON osm_poi_polygon