gistfile1.txt

#!/usr/bin/env ruby

require 'rubygems'
require 'sqlite3'
require 'benchmark'
require File.expand_path("../../../load_paths", __FILE__)
require 'active_record'

ActiveRecord::Base.establish_connection(:adapter => 'sqlite3',
                                        :database => ':memory:')

class User < ActiveRecord::Base
  connection.create_table :users, :force => true do |t|
  end
end

Benchmark.bm do |x|
  x.report 'Model#find_by_id' do
    100_000.times do
      User.find_by_id(1)
    end
  end
end

# MRI 1.8.7
# without caching find_by_* methods
#                  user        system    total     real
# Model#find_by_id 33.050000   1.060000  34.110000 ( 37.705276)

# caching find_by_* methods 
#                  user        system    total     real
# Model#find_by_id 29.550000   0.880000  30.430000 ( 31.797355)


# MRI 1.9.2
# without caching find_by_* methods
#                  user        system    total     real
# Model#find_by_id 25.250000   0.170000  25.420000 ( 27.110316)

# caching find_by_* methods 
#                  user        system    total     real
# Model#find_by_id 23.190000   0.140000  23.330000 ( 24.353884)