I''m trying to track down why Rails 4.1.0 beta is more than twice as slow as Rails 3.2.13 when performing a standard MyModel.includes(:some_association) query. I''ve already patched an issue that caused it to be 31 times slower, (see https://github.com/rails/rails/pull/12090), but the remaining delta is still prohibitively slow (at least for our app). I''m testing by running the following code (see https://gist.github.com/njakobsen/6393783 for a simple test suite). RubyProf.start Item.includes(:people).limit(1000).order(:id).to_a result = RubyProf.stop printer = RubyProf::GraphHtmlPrinter.new(result) printer.print(File.open("../rails-include-performance-#{Rails.version}.html", ''w'')) One interesting thing I noticed using Ruby prof was that while Rails 3.2.13 made 10145 calls to Class#new, Rails 4.1.0 beta called it 67154 times while running the same test. Now, I''m not familiar with all the fundamental differences between Rails 3 vs Rails 4, but it seems like we''re now making a ton more objects, and it''s having a serious impact on performance. Is there anyone familiar with the association preloader function, or someone who is working on performance tuning Rails 4 so I can help make it as fast as Rails 3 was? Nicholas. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Core" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-core+unsubscribe@googlegroups.com. To post to this group, send email to rubyonrails-core@googlegroups.com. Visit this group at http://groups.google.com/group/rubyonrails-core. For more options, visit https://groups.google.com/groups/opt_out.