CREATE OR REPLACE FUNCTION consolidate()
  RETURNS double precision AS
$BODY$ DECLARE
  sql_amounts text;
  id integer;

  r integer;
  v_row integer[];

  amount double precision;
  v_amount double precision[];

  -- Model for the "average" values.
  v_model xy;

  date_day integer;
  date_month integer;

  result double precision;
  max_row integer;
BEGIN
  FOR date_day, date_month IN
    SELECT
      extract( day from date '2000-01-01' + s.a ),
      extract( month from date '2000-01-01' + s.a )
    FROM
      generate_series( 0, 365, 1 ) AS s( a )
  LOOP

  -- Iterate over all the city ids.
  FOR id IN
    SELECT
      ci.id
    FROM
      city ci,
      region re,
      country co
    WHERE
      ci.region_id = re.id AND
      re.country_id = co.id AND
      co.id = 27
    ORDER BY
      co.id,
      re.id,
      ci.name
  LOOP
    sql_amounts := '
      SELECT
        row_number() OVER (ORDER BY taken)::integer,
        avg( amount )::double precision
      FROM
        city_stations( '||id||', 25 ) ca,
        measurement m
      WHERE
        m.category_id = 1 AND
        m.station_id = ca.id AND
        extract( month from m.taken ) = '||date_month||' AND
        extract( day from m.taken ) = '||date_day||'
      GROUP BY
        m.taken
      ORDER BY
        m.taken';

    v_model := NULL;
    v_row := NULL;
    v_amount := NULL;

    FOR r, amount IN
      EXECUTE sql_amounts
    LOOP
      SELECT array_append( v_row, r::integer ) INTO v_row;
      SELECT array_append( v_amount, amount::double precision ) INTO v_amount;
    END LOOP;

    max_row := array_upper( v_amount, 1 );

    IF max_row > 3 THEN
      SELECT * INTO v_model FROM plr_model_gam( v_row, v_amount );
      result := v_model.y[ max_row ];
    END IF;
  END LOOP;

  -- Iterate once while testing optimizations...
  EXIT;
  END LOOP;

  RETURN result;
END;
$BODY$
  LANGUAGE plpgsql VOLATILE;