def self.update_rank_by klass

gistfile1.txt

 def self.update_rank_by klass
    rank_class = (klass.name + "Rank").constantize
    rank_by_col = "#{klass.name.underscore}_id".to_sym        
 
    rank = total_points = rank_by = 0
 
    sum_points_by(rank_class, rank_by_col).find_in_batches do |points|
    User.transaction do
      points.each do |point|
        rank_by_col_val = point.send(rank_by_col) 
 
        # calculate rank
        if ( rank_by != rank_by_col_val)
          rank = total_points = 0
          rank_by = rank_by_col_val
        end
 
#i changed game.total_points to point.points        
        if point.total_points > total_points
 
#i changed game.total_points to point.points        
          total_points = point.total_points
          rank +=1
        end
 
# i passed rank - i was getting an error that rank was not known to create_or_update_rank_object
        create_or_update_rank_object(rank_class, rank_by_col, point.user_id, rank_by_col_val, point.total_points, rank)
      end
    end      
    end    
  end
 
 
# i added rank_class here because it was being passed above - not sure if it should have been removed as a parameter above
  def self.sum_points_by(rank_class, rank_by_col)
    select_sql = "points.user_id, points.#{rank_by_col}, 
                  SUM(points.points) total_points"
    Point.select(select_sql).group(:user_id, rank_by_col).
      order("#{rank_by_col}, total_points DESC")
  end
 
# i passed in rank because i was geting an error that 'rank' was undefined
  def self.create_or_update_rank_object(rank_class, rank_by_col, user_id, rank_by_col_val, total_points, rank)
    ro = rank_class.send(
      "find_or_initialize_by_user_id_and_#{rank_by_col}",
      user_id, rank_by_col_val)
    ro.total_points = total_points           
    ro.rank = rank
    ro.save
  end
 
 
Points table:
        points  user_id         game_type_id    game_id
        10        1		1	        1
	10	1		1	        1
	20	2		1	        2
	10	2		1	        2
	25	2		1	        3
	20	2		1       	1
	15	1		1	        2
 
GameRanks (actual):
        user_id         game_id         total_points    rank
        1               1	        20	        1
        2	        1	        20	        1
        2	        2	        30	        1
        1	        2	        15	        1
        2	        3	        25	        1
 
GameRanks (expected):
        user_id         game_id         total_points    rank
        1               1               20	        1
        2	        1	        20	        1
        2	        2	        30	        1
        1	        2	        15	        2  <= expected to be 2
        2	        3	        25	        1
 
 
GameTypeRanks (actual - correct as-is):
        user_id         game_type_id    total_points    rank
        1               1	        35	        1
        2	        1	        75	        2
 
Trace:
irb(main):001:0> User.update_rank
Scoped order and limit are ignored, it's forced to be batch order and batch size
  Point Load (1.1ms)  SELECT points.user_id, points.game_id,
 SUM(points.points) total_points FROM `points` WHERE (`points`.`id` >= 0) GROUP BY user_id, game_id ORDER BY `points`.`id` ASC LIMIT 1000
   (0.6ms)  BEGIN
  GameRank Load (0.8ms)  SELECT `game_ranks`.* FROM `game_ranks` WHERE `game_ranks`.`user_id` = 1 AND `game_ranks`.`game_id` = 1 LIMIT 1
  GameRank Load (0.6ms)  SELECT `game_ranks`.* FROM `game_ranks` WHERE `game_ranks`.`user_id` = 2 AND `game_ranks`.`game_id` = 2 LIMIT 1
   (20.2ms)  UPDATE `game_ranks` SET `rank` = 1, `updated_at` = '2013-03-06 05:29:26' WHERE `game_ranks`.`id` = 2
  GameRank Load (0.7ms)  SELECT `game_ranks`.* FROM `game_ranks` WHERE `game_ranks`.`user_id` = 2 AND `game_ranks`.`game_id` = 3 LIMIT 1
   (0.5ms)  UPDATE `game_ranks` SET `rank` = 1, `updated_at` = '2013-03-06 05:29:26' WHERE `game_ranks`.`id` = 3
  GameRank Load (0.5ms)  SELECT `game_ranks`.* FROM `game_ranks` WHERE `game_ranks`.`user_id` = 2 AND `game_ranks`.`game_id` = 1 LIMIT 1
   (0.6ms)  UPDATE `game_ranks` SET `rank` = 1, `updated_at` = '2013-03-06 05:29:26' WHERE `game_ranks`.`id` = 4
  GameRank Load (0.6ms)  SELECT `game_ranks`.* FROM `game_ranks` WHERE `game_ranks`.`user_id` = 1 AND `game_ranks`.`game_id` = 2 LIMIT 1
  SQL (0.5ms)  INSERT INTO `game_ranks` (`created_at`, `rank`, `game_id`, `total_points`, `updated_at`, `user_id`) VALUES ('2013-03-06 05:29:26', 1, 2, 15, '2013-03-06 05:29:26', 1)
   (19.5ms)  COMMIT
Scoped order and limit are ignored, it's forced to be batch order and batch size
  Point Load (0.7ms)  SELECT points.user_id, points.game_type_id,
 SUM(points.points) total_points FROM `points` WHERE (`points`.`id` >= 0) GROUP BY user_id, game_type_id ORDER BY `points`.`id` ASC LIMIT 1000
   (0.5ms)  BEGIN
  GameTypeRank Load (0.7ms)  SELECT `game_type_ranks`.* FROM `game_type_ranks` WHERE `game_type_ranks`.`user_id` = 1 AND `game_type_ranks`.`game_type_id` = 1 LIMIT 1
   (1.0ms)  UPDATE `game_type_ranks` SET `total_points` = 35, `updated_at` = '2013-03-06 05:29:26' WHERE `game_type_ranks`.`id` = 1
  GameTypeRank Load (0.6ms)  SELECT `game_type_ranks`.* FROM `game_type_ranks` WHERE `game_type_ranks`.`user_id` = 2 AND `game_type_ranks`.`game_type_id` = 1 LIMIT 1
   (19.6ms)  COMMIT
=> nil