Simple CSV Parser vs. CSV Gem Benchmark

csv_parser_csv_gem_benchmark.rb

require 'open-uri'
require 'nokogiri'
require 'parslet'
require 'csv'


# --------------------------------------------------
# Auxiliary code

class String
  def unquote
    self.gsub(/(^"|"$)/,"").gsub(/""/,'"')
  end
end


def time &block
  t1 = Time.now
  block.call if block_given?
  t2 = Time.now
  puts t2-t1
end

# --------------------------------------------------
# Fetching test data
doc  = Nokogiri::HTML(open('https://github.com/circle/fastercsv/blob/master/test/test_data.csv'))

data = doc.css('pre div.line').inject("") do |result, link|
  result << link.content << "\n"
  result
end

# --------------------------------------------------
# CSV parser

class Parser < Parslet::Parser

  rule(:file)        {(record.as(:row) >> newline).repeat(1)}
  rule(:record)      {field.as(:column) >> (comma >> field.as(:column)).repeat}
  rule(:field)       {escaped | non_escaped}
  rule(:escaped)     {d_quote >> (textdata | comma | cr | lf | d_quote >> d_quote).repeat >> d_quote}
  rule(:non_escaped) {textdata.repeat}
  rule(:textdata)    {((comma | d_quote | cr | lf).absent? >> any).repeat(1)}
  rule(:newline)     {lf >> cr.maybe}
  rule(:lf)          {str("\n")}
  rule(:cr)          {str("\r")}
  rule(:d_quote)     {str('"')}
  rule(:comma)       {str(',')} 

  root(:file)
end

class Transformer < Parslet::Transform

  rule(:column => subtree(:field)) do
    if field.is_a?(Array) # = empty array []
      nil
    else 
      field.to_s.unquote
    end
  end

  rule(:row => subtree(:array)) {array}
end

# --------------------------------------------------
# Benchmark

# CSV parser
time do
  tree = Parser.new.parse(data)
  Transformer.new.apply(tree)
end
# => 33.771940832


# CSV gem
time do 
  CSV.parse(data)
end
# => 0.040131919