Benchmarking of ways of extracting single value from large YAML map (e.g. ActiveRecord serialized data)

yaml_value_extraction_benchmarks.rb

require 'yaml'
require 'benchmark'

def make_yaml_string(num_entries=500)
  entry_nums = (0...num_entries).to_a
  entry_nums.shuffle!
  result = ''
  entry_nums.each do |n|
    result << "something_#{n}: #{Random.rand}\n"
  end
  result
end


puts 'Build a lot of big YAML strings to parse ...'
yaml_strings = Array.new(500){ make_yaml_string }


puts '', 'Extract a specific value using YAML.load ...'

last_extracted_value = 'n/a'
bench = Benchmark.measure do
  yaml_strings.each do |yaml_string|
    data = YAML.load(yaml_string)
    last_extracted_value = data['something_99']
  end
end

puts "Last value extracted: #{last_extracted_value}"

puts "Benchmark results:"
puts bench

# ===== OUTPUT =====
# Extract a specific value using YAML.load ...
# Last value extracted: 0.06597329553649589
# Benchmark results:
#   4.800000   0.020000   4.820000 (  4.813697)


# The Psych handler to extract the value for the "something_99" key.

class ExtractionHandler < YAML::Handler
  class DoneExtracting < StandardError ; end

  attr_accessor :something_99, :bail_when_done

  def start_mapping(*)
    self.depth += 1
    self.is_key = true
  end

  def end_mapping(*)
    self.depth -= 1
  end

  def scalar(value, *args)
    return unless depth == 1
    if is_key
      self.is_something_99 = (value == 'something_99')
    elsif is_something_99
      self.something_99 = value
      raise DoneExtracting if bail_when_done
    end
    self.is_key = !is_key
  end

  attr_writer :depth

  def depth
    @depth ||= 0
  end

  attr_accessor :is_key, :is_something_99
end


puts '', 'Extract a specific value using YAML parser & custom handler'

last_extracted_value = 'n/a'
bench = Benchmark.measure do
  yaml_strings.each do |yaml_string|
    h = ExtractionHandler.new
    p = YAML::Parser.new(h)

    begin
      p.parse yaml_string
    rescue ExtractionHandler::DoneExtracting
    end

    last_extracted_value = h.something_99
  end
end

puts "Last value extracted: #{last_extracted_value}"

puts "Benchmark results:"
puts bench

# ===== OUTPUT =====
# Extract a specific value using YAML parser & custom handler
# Last value extracted: 0.06597329553649589
# Benchmark results:
#   1.080000   0.010000   1.090000 (  1.089758)


puts '', 'Extract a specific value using YAML parser & custom handler and bail-when-done'

last_extracted_value = 'n/a'
bench = Benchmark.measure do
  yaml_strings.each do |yaml_string|
    h = ExtractionHandler.new
    h.bail_when_done = true
    p = YAML::Parser.new(h)

    begin
      p.parse yaml_string
    rescue ExtractionHandler::DoneExtracting
    end

    last_extracted_value = h.something_99
  end
end

puts "Last value extracted: #{last_extracted_value}"

puts "Benchmark results:"
puts bench

# ===== OUTPUT =====
# Extract a specific value using YAML parser & custom handler and bail-when-done
# Last value extracted: 0.06597329553649589
# Benchmark results:
#   0.540000   0.000000   0.540000 (  0.547873)


puts '', 'Extract a specific value using regular expression'

last_extracted_value = 'n/a'

regexp = /^ *something_99\s*:\s*(.*)\s*$/
bench = Benchmark.measure do
  yaml_strings.each do |yaml_string|
    match = regexp.match(yaml_string)
    last_extracted_value = match[1]
  end
end

puts "Last value extracted: #{last_extracted_value}"

puts "Benchmark results:"
puts bench

# ===== OUTPUT =====
# Extract a specific value using regular expression
# Last value extracted: 0.06597329553649589
# Benchmark results:
#   0.100000   0.000000   0.100000 (  0.097476)