Class: ActiveRecord::Turntable::Algorithm::RangeBsearchAlgorithm

Inherits:
Base
  • Object
show all
Defined in:
lib/active_record/turntable/algorithm/range_bsearch_algorithm.rb

Instance Method Summary collapse

Methods inherited from Base

#initialize

Constructor Details

This class inherits a constructor from ActiveRecord::Turntable::Algorithm::Base

Instance Method Details

#choose(shard_maps, key) ⇒ Object

Raises:



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# File 'lib/active_record/turntable/algorithm/range_bsearch_algorithm.rb', line 3

def choose(shard_maps, key)
  shard_map = shard_maps.bsearch { |shard| key <= shard.range.max }
  raise ActiveRecord::Turntable::CannotSpecifyShardError, "cannot specify shard for key:#{key.inspect}" unless shard_map
  shard_map.shard
end

#choose_index(shard_maps, key) ⇒ Object 



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# File 'lib/active_record/turntable/algorithm/range_bsearch_algorithm.rb', line 9

def choose_index(shard_maps, key)
  (0...shard_maps.size).bsearch { |idx| key <= shard_maps[idx].range.max } or
    raise ActiveRecord::Turntable::CannotSpecifyShardError, "cannot specify shard for key:#{key.inspect}"
end

#shard_weights(shard_maps, current_sequence_value) ⇒ Object 



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# File 'lib/active_record/turntable/algorithm/range_bsearch_algorithm.rb', line 14

def shard_weights(shard_maps, current_sequence_value)
  current_shard_index = choose_index(shard_maps, current_sequence_value)
  shard_maps = shard_maps[0..current_shard_index]
  weights_hash = Hash.new { |h, k| h[k] = 0 }
  shard_maps.each_with_index do |shard_map, idx|
    weights_hash[shard_map.shard] += if idx < current_shard_index
                                       shard_map.range.size
                                     else
                                       current_sequence_value - shard_map.range.min + 1
                                     end
  end
  weights_hash
end