require 'mongoid'
class Product
  include Mongoid::Document
  field :title,  type: String
  embeds_many :specs,  class_name: 'Product::Spec'
  embeds_many :photos,  class_name: 'Product::Photo'
end

class Product::Spec
  include Mongoid::Document
  field :name, type: String
  field :value
  embedded_in :product
end

class Product::Photo
  include Mongoid::Document
  field :image,        type: String
  embedded_in :product
end
Mongoid.load! "mongoid.yml", :development
Mongo::Logger.logger.level = 0

Product.destroy_all

product = Product.new(title: "BMW X5")
product.specs = [{name: "make", value: "BMW"}, {name: "model", value: "X5"}]
product.photos = [{image: "http://example.com/"}]
product.save
#D, [2015-12-29T12:46:11.473895 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.insert | STARTED | {"insert"=>"products", "documents"=>[{"_id"=>BSON::ObjectId('5682809356c02c15c800000c'), "title"=>"BMW X5", "specs"=>[{"_id"=>BSON::ObjectId('5682809356c02c15c800000d'), "name"=>"make", "value"=>"BMW"}, {"_id"=>BSON::ObjectId('5682809356c02c15c800000e...
#D, [2015-12-29T12:46:11.475939 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.insert | SUCCEEDED | 0.000782928s
#Works As expected, all updates in save methods

product = Product.all.first
#D, [2015-12-29T12:46:14.962596 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.find | STARTED | {"find"=>"products", "filter"=>{}, "limit"=>-1}
#D, [2015-12-29T12:46:14.964863 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.find | SUCCEEDED | 0.00184706s
product.specs = [{name: "make", value: "BMW"}, {name: "model", value: "X5"}]
#D, [2015-12-29T12:46:14.985404 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.update | STARTED | {"update"=>"products", "updates"=>[{"q"=>{"_id"=>BSON::ObjectId('5682809356c02c15c800000c')}, "u"=>{"$set"=>{"specs"=>[{"_id"=>BSON::ObjectId('5682809656c02c15c8000010'), "name"=>"make", "value"=>"BMW"}, {"_id"=>BSON::ObjectId('5682809656c02c15c800001...
#D, [2015-12-29T12:46:14.986820 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.update | SUCCEEDED | 0.0010425179999999999s
#Unexpected autosave


product.attributes = {title: "X5 2", specs: [{name: "make", value: "BMW"}, {name: "model", value: "X5"}]}
photos = product.photos 
product.photos = product.photos 
#D, [2015-12-29T12:46:20.393142 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.update | STARTED | {"update"=>"products", "updates"=>[{"q"=>{"_id"=>BSON::ObjectId('5682809356c02c15c800000c')}, "u"=>{"$set"=>{"photos"=>[{"_id"=>BSON::ObjectId('5682809356c02c15c800000f'), "image"=>"http://example.com/"}]}}, "multi"=>false, "upsert"=>false}], "writeCo...
#D, [2015-12-29T12:46:20.394359 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.update | SUCCEEDED | 0.0007998819999999999s
#Unexpected autosave that cause next statement bug
product.save 
#D, [2015-12-29T12:46:24.597950 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.update | STARTED | {"update"=>"products", "updates"=>[{"q"=>{"_id"=>BSON::ObjectId('5682809356c02c15c800000c')}, "u"=>{"$set"=>{"title"=>"X5 2"}, "$pushAll"=>{"specs"=>[{"_id"=>BSON::ObjectId('568280a056c02c15c8000012'), "name"=>"make", "value"=>"BMW"}, {"_id"=>BSON::Ob...
#D, [2015-12-29T12:46:24.599487 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.update | SUCCEEDED | 0.000984854s
#Unexpected pushAll query without clearing old items cause

product.reload.specs.size 
#D, [2015-12-29T12:46:29.502394 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.find | STARTED | {"find"=>"products", "filter"=>{:_id=>BSON::ObjectId('5682809356c02c15c800000c')}}
#D, [2015-12-29T12:46:29.503874 #5576] DEBUG -- : MONGODB | 192.168.33.11:27017 | mongo_test.find | SUCCEEDED | 0.001167992s
# Unexpected 4