Support motorway highway labels for lower zooms

layers/highway_name/merge_highways.sql

@@ -10,20 +10,43 @@ CREATE TABLE IF NOT EXISTS osm_highway_name_linestring AS (
 		member_osm_ids[0] AS osm_id,
 		member_osm_ids,
 		name,
+        ref,
 		highway,
 		z_order
 	FROM (
 		SELECT
 			ST_LineMerge(ST_Union(geometry)) AS geometry,
 			name,
+            ref,
 			highway,
 			min(z_order) AS z_order,
 			array_agg(DISTINCT osm_id) AS member_osm_ids
 	    FROM osm_highway_linestring
         -- We only care about roads for labelling
-	    WHERE name <> ''
-	    GROUP BY name, highway
+	    WHERE name <> '' OR ref <> ''
+	    GROUP BY name, highway, ref
 	) AS highway_union
 );
 
-CREATE INDEX IF NOT EXISTS osm_highway_name_linestring_geometry_idx ON osm_important_place_point USING gist(geometry);
+CREATE INDEX IF NOT EXISTS osm_highway_name_linestring_geometry_idx ON osm_highway_name_linestring USING gist(geometry);
+
+CREATE TABLE IF NOT EXISTS osm_highway_name_linestring_gen1 AS (
+    SELECT ST_Simplify(geometry, 50) AS geometry, osm_id, member_osm_ids, name, ref, highway, z_order
+    FROM osm_highway_name_linestring
+    WHERE highway IN ('motorway','trunk')  AND ST_Length(geometry) > 8000
+);
+CREATE INDEX IF NOT EXISTS osm_highway_name_linestring_gen1_geometry_idx ON osm_highway_name_linestring_gen1 USING gist(geometry);
+
+CREATE TABLE IF NOT EXISTS osm_highway_name_linestring_gen2 AS (
+    SELECT ST_Simplify(geometry, 120) AS geometry, osm_id, member_osm_ids, name, ref, highway, z_order
+    FROM osm_highway_name_linestring_gen1
+    WHERE highway IN ('motorway','trunk')  AND ST_Length(geometry) > 14000
+);
+CREATE INDEX IF NOT EXISTS osm_highway_name_linestring_gen2_geometry_idx ON osm_highway_name_linestring_gen2 USING gist(geometry);
+
+CREATE TABLE IF NOT EXISTS osm_highway_name_linestring_gen3 AS (
+    SELECT ST_Simplify(geometry, 120) AS geometry, osm_id, member_osm_ids, name, ref, highway, z_order
+    FROM osm_highway_name_linestring_gen2
+    WHERE highway = 'motorway' AND ST_Length(geometry) > 20000
+);
+CREATE INDEX IF NOT EXISTS osm_highway_name_linestring_gen3_geometry_idx ON osm_highway_name_linestring_gen3 USING gist(geometry);