Add aeroway layer

layers/aeroway/layer.sql

@@ -0,0 +1,20 @@
+-- etldoc: layer_aeroway[shape=record fillcolor=lightpink, style="rounded,filled",
+-- etldoc:     label="layer_aeroway |<z12> z12|<z13> z13|<z14> z14" ];
+
+CREATE OR REPLACE FUNCTION layer_aeroway(bbox geometry, zoom_level int)
+RETURNS TABLE(geometry geometry, class text) AS $$
+    SELECT geometry, aeroway AS class FROM (
+        -- etldoc:  aeroway_z12 -> layer_aeroway:z12
+        SELECT geometry, aeroway
+        FROM osm_aeroway_polygon_gen2 WHERE zoom_level = 12
+        UNION ALL
+        -- etldoc:  aeroway_z13 -> layer_aeroway:z13
+        SELECT geometry, aeroway
+        FROM osm_aeroway_polygon_gen1 WHERE zoom_level = 13
+        UNION ALL
+        -- etldoc:  aeroway_z14 -> layer_aeroway:z14_
+        SELECT geometry, aeroway
+        FROM osm_aeroway_polygon WHERE zoom_level >= 14
+    ) AS zoom_levels
+    WHERE geometry && bbox;
+$$ LANGUAGE SQL IMMUTABLE;