dig benchmark for fluentd

dig_bench.rb

require 'benchmark'

class Test0
  def initialize(key)
    @key = key
  end

  def call(record)
    record[@key]
  end
end

class Test1
  def initialize(keys)
    @keys = keys
  end

  def call(record)
    record.dig(*@keys)
  end
end

class Test2
  def initialize(keys)
    __str_eval_code__ = create_handler(keys)

    (class << self; self; end).class_eval <<-EORUBY,  __FILE__, __LINE__ + 1
      def call(r)
        #{__str_eval_code__}
      end
    EORUBY
  end

  def call(r)
  end
end

def create_handler(keys)
  args = []
  keys.each { |key|
    case key
    when String
      args << "'#{key}'.freeze"
    when Integer
      args << key.to_s 
    else
      raise "Unsupported key type: #{key}"
    end
  }
  "r.dig(#{args.join(',')})"
end

h = {'foo' => {'bar' => [0, 1, 2]}}
keys = ['foo', 'bar', 1]
n = 5000000

t0 = Test0.new('foo') # baseline
t1 = Test1.new(keys)
t2 = Test2.new(keys)

os1 = os2 = os3 = os4 = nil
GC.disable

Benchmark.bm do |x|
  x.report { 
    n.times do
      t0.call(h)
    end
  }
  x.report { 
    #os1 = ObjectSpace.count_objects
    n.times do
      t1.call(h)
    end
    #os2 = ObjectSpace.count_objects
  }
  x.report {
    #os3 = ObjectSpace.count_objects
    n.times do
      t2.call(h)
    end
    #os4 = ObjectSpace.count_objects
  }
end