JRuby $LOAD_PATH index speeds up Bundler.require in a Rails app (at top of application.rb)

comments

Rails 3.1.8 app in Ruby 1.8 compatibility mode with ~65 dependencies
(not sure how many in total including
transient deps) was timed up to the Bundler.require line in config/application.rb
(JRuby 1.7.0)

Before: 18.8 seconds
After:  15.9 seconds

This likely seriously breaks the semantics of 'require', and maybe isn't faster
enough to be worth it.

hacks_upon_hacks.rb

$LOAD_PATH_INDEX = {}

alias :__orig_require__ :require

def require(name)
  # Underlying $LOADED_FEATURES is actually an StringArraySet, so should
  # have O(1) lookup.

  feature = name + '.rb'
  if !$LOADED_FEATURES.include?(feature) && abs = $LOAD_PATH_INDEX[feature]
    $LOADED_FEATURES << feature
    __orig_require__(abs)
  else
    __orig_require__(name)
  end
end

start = Time.now
$LOAD_PATH.each do |path|
  next if path == '.'

  Dir[path + '/**/*.rb'].each do |rb|
    # Strip off the path portion plus extra /.
    # What remains is what one would pass as an arg to a require with
    # an extra '.rb'.
    feature = rb.slice((path.length+1)..(-1))
    
    # first in load path order wins
    $LOAD_PATH_INDEX[feature] ||= rb
  end
end
puts "INDEXED ALL #{$LOAD_PATH_INDEX.size} THINGS! #{Time.now - start}"