CREATE OR REPLACE FUNCTION layer_city(bbox geometry, zoom_level int, pixel_width numeric)
RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, class city_class, "rank" int) AS $$
    SELECT osm_id, geometry, name, name_en, place, "rank"
    FROM osm_city_point
    WHERE geometry && bbox
      AND ((zoom_level = 2 AND "rank" = 0)
        OR (zoom_level BETWEEN 3 AND 7 AND "rank" < zoom_level)
      )
    UNION ALL
    SELECT osm_id, geometry, name, name_en, place, "rank" FROM (
        SELECT osm_id, geometry, name, name_en, place, "rank",
			row_number() OVER (
				PARTITION BY LabelGrid(geometry, 150 * pixel_width)
				ORDER BY place ASC NULLS LAST,
				population DESC NULLS LAST,
				length(name) DESC
			) AS gridrank
        FROM osm_city_point
        WHERE geometry && bbox
          AND ((zoom_level BETWEEN 8 AND 9 AND place <= 'town'::city_class)
            OR (zoom_level = 10 AND place <= 'village'::city_class)
            OR (zoom_level BETWEEN 11 AND 13 AND place <= 'suburb'::city_class)
            OR (zoom_level >= 14)
          )
    ) AS ranked_places
    WHERE (zoom_level = 8 AND gridrank <= 4)
       OR (zoom_level BETWEEN 9 AND 12 AND gridrank <= 9)
       OR (zoom_level >= 13);
$$ LANGUAGE SQL IMMUTABLE;