dumb_test.rb

#testing the speed of creating a new object via the association with mongoid

c = Club.first

#######  43 seconds #######
begin
  500.times do |i|
    c.people.create(:name => 'Jim')
  end
end


####### 1 second #########
begin
  club_id = c._id
  500.times do |i|
    Person.create(:name => 'Jim', :club_id => club_id)
  end
end

Why is there such a performance difference?