Performance comparison before/after https://github.com/rails/rails/compare/07f90f6...6bff643
$ N=50000 bundle exec ruby examples/performance.rb
Generating data...
Inserting 10,000 users and exhibits...
user system total real
Model#id (x5000000) 3.230000 0.000000 3.230000 ( 3.250757)