Contents

# -*- coding: utf-8 -*-
module ActiveRecord::Turntable::Algorithm
  class RangeAlgorithm < Base
    def initialize(config)
      @config = config
    end

    def calculate(key)
      idx = calculate_idx(key)
      @config[:shards][idx][:connection]
    rescue
      raise ActiveRecord::Turntable::CannotSpecifyShardError, "cannot specify shard for key:#{key}"
    end

    def calculate_idx(key)
      @config[:shards].find_index { |h| h[:less_than] > key }
    end

    # { connection_name => weight, ... }
    def calculate_used_shards_with_weight(sequence_value)
      idx = calculate_idx(sequence_value)
      last_connection = calculate(sequence_value)
      shards = @config[:shards][0..idx]
      weighted_hash = Hash.new { |h, k| h[k] = 0 }
      prev_max = 0
      shards.each_with_index do |h, idx|
        weighted_hash[h[:connection]] += if idx < shards.size - 1
                                            h[:less_than] - prev_max - 1
                                          else
                                            sequence_value - prev_max
                                          end
        prev_max = h[:less_than] - 1
      end
      weighted_hash
    end
  end
end

Version data entries

3 entries across 3 versions & 1 rubygems

Version	Path
activerecord-turntable-3.0.0.alpha3	lib/active_record/turntable/algorithm/range_algorithm.rb
activerecord-turntable-3.0.0.alpha2	lib/active_record/turntable/algorithm/range_algorithm.rb
activerecord-turntable-3.0.0.alpha1	lib/active_record/turntable/algorithm/range_algorithm.rb