Mongoid array timings

gistfile1.rb

#188s
(0..10000).each do
  document1.sub_documents << document2
end

#119s
(0..10000).each do
  document1.push(:sub_document_ids, document2._id)
end

#76s
(0..10000).each do
  document1.add_to_set(:sub_document_ids, document2._id)
end

#1s
(0..10000).each do
  document1.sub_document_ids << document2._id
end