Add highway names

layers/highway_name/merge_highways.sql

@@ -0,0 +1,29 @@
+-- Instead of using relations to find out the road names we
+-- stitch together the touching ways with the same name
+-- to allow for nice label rendering
+-- Because this works well for roads that do not have relations as well
+CREATE TABLE IF NOT EXISTS osm_highway_name_linestring AS (
+	SELECT
+		(ST_Dump(geometry)).geom AS geometry,
+        -- NOTE: The osm_id is no longer the original one which can make it difficult
+        -- to lookup road names by OSM ID
+		member_osm_ids[0] AS osm_id,
+		member_osm_ids,
+		name,
+		highway,
+		z_order
+	FROM (
+		SELECT
+			ST_LineMerge(ST_Union(geometry)) AS geometry,
+			name,
+			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
+	) AS highway_union
+);
+
+CREATE INDEX IF NOT EXISTS osm_highway_name_linestring_geometry_idx ON osm_important_place_point USING gist(geometry);