placenames_medium.mss

#placenames-medium {
  [capital = 'yes'] {
    [zoom >= 5][zoom < 15] {
      text-name: "[name]";
      text-size: 10;
      text-fill: @placenames;
      text-face-name: @book-fonts;
      text-halo-radius: 1.5;
      text-min-distance: 10;
      [zoom >= 6] {
        text-size: 12;
      }
      [zoom >= 11] {
        text-size: 15;
      }
    }
  }

  [place = 'city'] {
    [zoom >= 6][zoom < 15] {
      text-name: "[name]";
      text-size: 9;
      text-fill: @placenames;
      text-face-name: @book-fonts;
      text-halo-radius: 1.5;
      text-min-distance: 10;
      [zoom >= 9] {
        text-size: 12;
      }
      [zoom >= 11] {
        text-size: 15;
      }
    }
  }

  [place = 'town'] {
    [zoom >= 9] {
      text-name: "[name]";
      text-size: 9;
      text-fill: @placenames;
      text-face-name: @book-fonts;
      text-halo-radius: 1.5;
      text-wrap-width: 20;
      text-min-distance: 10;
    }
    [zoom >= 11] {
      text-size: 11;
    }
    [zoom >= 14] {
      text-size: 15;
      text-fill: @placenames-light;
    }
  }
}

query.sql

SELECT place,name,capital,population FROM (SELECT way,place,name,capital,population,way_area
  FROM
    (SELECT 
        way,place,name,NULL AS capital,way_area, -- The polygon table doesn't have the capital information with the default style
        CASE WHEN population~E'^\\d{1,9}$' THEN population::integer ELSE NULL END AS population
          -- We need to filter out population values that might cause exceptions. This is a fairly rigerous filtering as it will remove population=1,000
      FROM planet_osm_polygon
    UNION ALL -- Join the two together
    SELECT 
        way,place,name,capital,NULL AS way_area, -- Points don't have an area
        CASE WHEN population~E'^\\d{1,9}$' AND length(population)<10 THEN population::integer ELSE NULL END AS population -- as above
      FROM planet_osm_point) AS p
  WHERE place IN ('city','town') -- This condition is brought inside by the query optimizer
  ORDER BY 
    CASE place WHEN 'city' THEN 0 ELSE 10 END, -- We don't actually need this at moment with the current MSS
    CASE capital WHEN 'yes' THEN 0 ELSE 10 END, -- Nor this
    way_area DESC NULLS LAST, -- Put physically larger first
    population DESC NULLS LAST -- For points (no area) put larger population first
) AS placenames_medium WHERE "way" && ST_SetSRID('BOX3D(-13932330.01959565 6105178.323193599,-12993071.8160274 7044436.526761843)'::box3d, 900913)

results.txt

┌───────┬──────────────────────────────┬─────────┬────────────┐
│ place │             name             │ capital │ population │
├───────┼──────────────────────────────┼─────────┼────────────┤
│ city  │ Sumas                        │ ¤       │          ¤ │
│ city  │ Vancouver                    │ ¤       │    2100000 │
│ city  │ Surrey                       │ ¤       │     400000 │
│ city  │ Victoria                     │ 4       │     330088 │
│ city  │ Kamloops                     │ ¤       │      85678 │
│ city  │ New Westminster              │ ¤       │      58000 │
│ city  │ Whistler                     │ ¤       │      11000 │
│ city  │ Revelstoke                   │ ¤       │          ¤ │