RoR - benchmark ActiveRecord Query

benchmark.rb

require 'benchmark'

n = 5 # Use any n you like
Benchmark.bmbm do |x|
  x.report("find by") { 
    n.times { User.find_by_name("Joe").id } 
  }
  x.report("select") { 
    n.times { User.find(:first, :select => :id, :conditions => ["name = ?","Joe"]).id } 
  }
end

# Reference
# 1. [http://ruby-doc.org/stdlib-2.6/libdoc/benchmark/rdoc/Benchmark.html](Rubydoc - Benchmark): 
#   The times for some benchmarks depend on the order in which items are run. 
#   These differences are due to the cost of memory allocation and garbage collection. 
#   To avoid these discrepancies, the bmbm method is provided. 
# 2. [https://stackoverflow.com/questions/3419220/benchmarking-rails-activerecord-queries](Benchmarking rails ActiveRecord Queries)
# 3. [Rails 2.3 benchmarker](https://github.com/rails/rails/blob/2-3-stable/railties/lib/commands/performance/benchmarker.rb)
# 4. [Rails 1.2 activerecord benchmarker](https://github.com/rails/rails/blob/1-2-stable/activerecord/benchmarks/benchmark.rb)
# 5. [Find when a file was deleted in git](https://stackoverflow.com/questions/6839398/find-when-a-file-was-deleted-in-git): git log --full-history -- your_file