pry.rb

[64] pry(main)> def run c, n=1000
[64] pry(main)*   ActiveRecord::Base.logger = nil
[64] pry(main)*   Foo.connection.uncached do
[64] pry(main)*     Benchmark.bm(10) do |b|
[64] pry(main)*       b.report(:exception) { n.times do; Foo.find(rand(1..c)) rescue nil; end }      
[64] pry(main)*       b.report(:find_by)   { n.times do; Foo.find_by(id: rand(1..c)); end }      
[64] pry(main)*     end  
[64] pry(main)*   end  
[64] pry(main)* end  
=> :run
[65] pry(main)> run ( Foo.count * 1.05 ).round;
                 user     system      total        real
exception    0.320000   0.010000   0.330000 (  0.395392)
find_by      0.310000   0.020000   0.330000 (  0.383363)
[66] pry(main)> run ( Foo.count * 2 ).round;
                 user     system      total        real
exception    0.330000   0.020000   0.350000 (  0.396790)
find_by      0.290000   0.010000   0.300000 (  0.358287)
[67] pry(main)> run ( Foo.count * 100 ).round;
                 user     system      total        real
exception    0.320000   0.020000   0.340000 (  0.390607)
find_by      0.300000   0.010000   0.310000 (  0.363125)