Handling ties

[stephenmckinney]

This could be more of a question then a bug, but with the below members, why wouldn't the ranking be: 1, 2, 2, 4 due to a tie?

>> lb = Leaderboard.new 'best_of'
>> lb.rank_member 1234, 100
>> lb.rank_member 1235, 100
>> lb.rank_member 1236, 101
>> lb.rank_member 1237, 99
>> lb.leaders(1)
[
  [0] {
    :member => "1236",
      :rank => 1,
     :score => 101.0
  },
  [1] {
    :member => "1235",
      :rank => 2,
     :score => 100.0
  },
  [2] {
    :member => "1234",
      :rank => 3,
     :score => 100.0
  },
  [3] {
    :member => "1237",
      :rank => 4,
     :score => 99.0
  }
]

[czarneckid]

Redis doesn't understand the notion of a "tie". From the documentation on ZREVRANGE, "Descending lexicographical order is used for elements with equal score." or ZRANGE, "Lexicographical order is used for elements with equal score."

[stephenmckinney]

Thanks for the quick reply and great gem.

[czarneckid]

If your values are going to be solely integers, it's possible you could use something along the lines of score.timestamp as proposed in this thread.

[stephenmckinney]

Thanks, but in this case the scores are floats. This tie situation mattered most for us when we needed to decide the winners of a leaderboard. So we decided on this:

def winners(options = {})
  leaders = leaders(1, options)
  leaders.take_while { |x| x[:score] == leaders.first[:score] }
end