gistfile1.txt

# instances method
def instances(&block)
  GC.enable_stats
  GC.clear_stats
  block.call
  warmup_objs = GC.num_allocations
  warmup_bytes = GC.allocated_size
  GC.clear_stats
  block.call
  puts "Objects:"
  puts "Warmup: #{warmup_objs} allocations | #{warmup_bytes} bytes"
  puts "Actual: #{GC.num_allocations} allocations | #{GC.allocated_size} bytes"
end


Account.destroy_all

a = Account.create(:email => '[email protected]')
50.times do |i|
  c = a.posts.create!(:title => "test", :body => "Loldel")
  10.times do
    c.comments.create!(:body => ("lol! " * 10))
  end
end


Account.first.posts(:include => :comments).map{|c| c.comments}.flatten.each do |comment|
  comment.post.account.email
end; nil

instances do 
  Account.first.posts(:include => :comments).map{|c| c.comments}.flatten.each do |comment|
    comment.post.account.email
  end
end

With IdentityMap disabled:

Warmup: 563328 allocations | 20273094 bytes
Actual: 562227 allocations | 20264239 bytes

With IdentityMap enabled:

Warmup: 116908 allocations | 3621494 bytes
Actual: 21108 allocations | 390139 bytes



Account.first(:include => {:posts => :comments}).posts.map(&:comments).flatten.each do |comment|
  comment.post.account.email
end; nil

instances do 
  Account.first(:include => {:posts => :comments}).posts.map(&:comments).flatten.each do |comment|
    comment.post.account.email
  end
end

With IdentityMap disabled:

Objects:
Warmup: 553832 allocations | 19720865 bytes
Actual: 553836 allocations | 19720860 bytes


With IdentityMap enabled:

Objects:
Warmup: 18401 allocations | 254328 bytes
Actual: 108517 allocations | 3078103 bytes