#801 add latest mat view and trigger function

gis/centreline/sql/create_matview_centreline_latest.sql

@@ -0,0 +1,19 @@
+CREATE MATERIALIZED VIEW gis_core.centreline_latest AS 
+SELECT *
+FROM gis_core.centreline
+WHERE version_date = (SELECT MAX(version_date) FROM gis_core.centreline); 
+
+CREATE TRIGGER refresh_trigger
+        AFTER INSERT OR UPDATE OR DELETE
+        ON gis_core.centreline
+        FOR EACH STATEMENT
+        EXECUTE PROCEDURE gis_core.centreline_latest_trigger(); 
+
+CREATE INDEX gis_core_centreline_latest_geom
+    ON gis_core.centreline_latest USING gist(geom);
+
+ALTER MATERIALIZED VIEW gis_core.centreline_latest OWNER TO gis_admins;
+
+GRANT SELECT ON gis_core.centreline_latest TO bdit_humans;
+
+COMMENT ON MATERIALIZED VIEW gis_core.centreline_latest IS 'Materialized view containing the latest version of centreline, derived from gis_core.centreline.'

gis/centreline/sql/create_trigger_centreline_latest.sql

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+CREATE OR REPLACE FUNCTION gis_core.centreline_latest_trigger()
+    RETURNS trigger 
+    LANGUAGE 'plpgsql'
+    COST 100
+    VOLATILE NOT LEAKPROOF SECURITY DEFINER
+AS $BODY$
+BEGIN
+
+REFRESH MATERIALIZED VIEW gis_core.centreline_latest;
+RETURN NULL;
+
+END;
+$BODY$;
+
+ALTER FUNCTION gis_core.centreline_latest_trigger() OWNER TO gis_admins;
+
+COMMENT ON FUNCTION gis_core.centreline_latest_trigger() IS 'Trigger fuction that refreshes the centreline_latest mat view after an update.';
+