has_many :bugs, :through => :rails

require 'benchmark'

Benchmark.bm do |x|
  n = 10000
  x.report do
    n.times do
      # "shit" exists
      Item.find_all_by_name "shit"
      Item.find_by_name "shit"      

      # "fud" does not exist
      Item.find_all_by_name "fud"
      Item.find_by_name "fud"
    end 
  end

  x.report do 
    n.times do  
      Item.find :all, :conditions => ["name = ?", "shit"]
      Item.find :first, :conditions => ["name = ?", "shit"]

      Item.find :all, :conditions => ["name = ?", "fud"]
      Item.find :first, :conditions => ["name = ?", "fud"]
    end 
  end
end

# $ script/runner benchmark.rb 
#       user     system      total        real
#  28.510000   1.270000  29.780000 ( 36.924108)
#  26.100000   1.230000  27.330000 ( 34.318721)