Create subclass attribute of railways

layers/transportation/layer.sql

@@ -6,13 +6,18 @@ $$ LANGUAGE SQL IMMUTABLE STRICT;
 -- etldoc: layer_transportation[shape=record fillcolor=lightpink, style="rounded,filled",
 -- etldoc:     label="<sql> layer_transportation |<z4> z4 |<z5> z5 |<z6> z6 |<z7> z7 |<z8> z8 |<z9> z9 |<z10> z10 |<z11> z11 |<z12> z12|<z13> z13|<z14_> z14+" ] ;
 CREATE OR REPLACE FUNCTION layer_transportation(bbox geometry, zoom_level int)
-RETURNS TABLE(osm_id bigint, geometry geometry, class text, ramp int, oneway int, brunnel TEXT, service TEXT) AS $$
+RETURNS TABLE(osm_id bigint, geometry geometry, class text, subclass text,
+ramp int, oneway int, brunnel TEXT, service TEXT) AS $$
     SELECT
         osm_id, geometry,
         CASE
             WHEN highway IS NOT NULL THEN highway_class(highway)
             WHEN railway IS NOT NULL THEN railway_class(railway)
         END AS class,
+        CASE
+            WHEN railway IS NOT NULL THEN railway
+            ELSE NULL
+        END AS subclass,
         -- All links are considered as ramps as well
         CASE WHEN highway_is_link(highway) OR highway = 'steps'
              THEN 1 ELSE is_ramp::int END AS ramp,

layers/transportation/transportation.yaml

@@ -30,6 +30,20 @@ layer:
       - raceway
       - rail
       - transit
+    subclass:
+      description: |
+          Distinguish more specific railway classes:
+          Subclass is value of the
+          [`railway`](http://wiki.openstreetmap.org/wiki/Key:railway) tag.
+      values:
+      - rail
+      - narrow_gauge
+      - preserved
+      - funicular
+      - subway
+      - light_rail
+      - monorail
+      - tram
     brunnel:
       description: |
           Mark whether way is a tunnel or bridge.
@@ -61,7 +75,7 @@ layer:
   datasource:
     geometry_field: geometry
     srid: 900913
-    query: (SELECT geometry, class, oneway, ramp, brunnel, service FROM layer_transportation(!bbox!, z(!scale_denominator!))) AS t
+    query: (SELECT geometry, class, subclass, oneway, ramp, brunnel, service FROM layer_transportation(!bbox!, z(!scale_denominator!))) AS t
 schema:
   - ./class.sql
   - ./update_transportation_merge.sql