Add ISO 3166-1 alpha-2 country codes as iso_a2 attribute

Fix #306

layers/place/layer.sql

@@ -3,7 +3,9 @@
 -- etldoc:     label="layer_place | <z0_3> z0-3|<z4_7> z4-7|<z8_11> z8-11| <z12_14> z12-z14+" ] ;
 
 CREATE OR REPLACE FUNCTION layer_place(bbox geometry, zoom_level int, pixel_width numeric)
-RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de text, tags hstore, class text, "rank" int, capital INT) AS $$
+RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text,
+    name_de text, tags hstore, class text, "rank" int, capital INT, iso_a2
+        TEXT) AS $$
 
     -- etldoc: osm_continent_point -> layer_place:z0_3
     SELECT
@@ -11,7 +13,8 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
         COALESCE(NULLIF(name_en, ''), name) AS name_en,
         COALESCE(NULLIF(name_de, ''), name, name_en) AS name_de,
         tags,
-        'continent' AS class, 1 AS "rank", NULL::int AS capital
+        'continent' AS class, 1 AS "rank", NULL::int AS capital,
+        NULL::text AS iso_a2
     FROM osm_continent_point
     WHERE geometry && bbox AND zoom_level < 4
     UNION ALL
@@ -25,7 +28,8 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
         COALESCE(NULLIF(name_en, ''), name) AS name_en,
         COALESCE(NULLIF(name_de, ''), name, name_en) AS name_de,
         tags,
-        'country' AS class, "rank", NULL::int AS capital
+        'country' AS class, "rank", NULL::int AS capital,
+        iso3166_1_alpha_2 AS iso_a2
     FROM osm_country_point
     WHERE geometry && bbox AND "rank" <= zoom_level + 1 AND name <> ''
     UNION ALL
@@ -39,7 +43,8 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
         COALESCE(NULLIF(name_en, ''), name) AS name_en,
         COALESCE(NULLIF(name_de, ''), name, name_en) AS name_de,
         tags,
-        'state' AS class, "rank", NULL::int AS capital
+        'state' AS class, "rank", NULL::int AS capital,
+        NULL::text AS iso_a2
     FROM osm_state_point
     WHERE geometry && bbox AND
           name <> '' AND
@@ -55,7 +60,8 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
         COALESCE(NULLIF(name_en, ''), name) AS name_en,
         COALESCE(NULLIF(name_de, ''), name, name_en) AS name_de,
         tags,
-        'island' AS class, 7 AS "rank", NULL::int AS capital
+        'island' AS class, 7 AS "rank", NULL::int AS capital,
+        NULL::text AS iso_a2
     FROM osm_island_point
     WHERE zoom_level >= 12
         AND geometry && bbox
@@ -68,7 +74,8 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
         COALESCE(NULLIF(name_en, ''), name) AS name_en,
         COALESCE(NULLIF(name_de, ''), name, name_en) AS name_de,
         tags,
-        'island' AS class, island_rank(area) AS "rank", NULL::int AS capital
+        'island' AS class, island_rank(area) AS "rank", NULL::int AS capital,
+        NULL::text AS iso_a2
     FROM osm_island_polygon
     WHERE geometry && bbox AND
         ((zoom_level = 8 AND island_rank(area) <= 3)
@@ -83,7 +90,8 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
     SELECT
         osm_id, geometry, name, name_en, name_de,
         tags,
-        place::text AS class, "rank", capital
+        place::text AS class, "rank", capital,
+        NULL::text AS iso_a2
     FROM layer_city(bbox, zoom_level, pixel_width)
     ORDER BY "rank" ASC
 $$ LANGUAGE SQL IMMUTABLE;

layers/place/place.yaml

@@ -34,6 +34,11 @@ layer:
       - suburb
       - neighbourhood
       - isolated_dwelling
+    iso_a2:
+      description: |
+          Two-letter country code [ISO 3166-1 alpha-2](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2).
+          Original value of the
+          [`country_code_iso3166_1_alpha_2`](http://wiki.openstreetmap.org/wiki/Tag:place%3Dcountry) tag.
     rank:
       description: |
           Countries, states and the most important cities all have a
@@ -53,7 +58,7 @@ layer:
   buffer_size: 256
   datasource:
     geometry_field: geometry
-    query: (SELECT geometry, name, name_en, name_de, {name_languages}, class, rank, capital FROM layer_place(!bbox!, z(!scale_denominator!), !pixel_width!)) AS t
+    query: (SELECT geometry, name, name_en, name_de, {name_languages}, class, rank, capital, iso_a2 FROM layer_place(!bbox!, z(!scale_denominator!), !pixel_width!)) AS t
 schema:
   - ./types.sql
   - ./capital.sql