在 Mongoid 2.2.0 上，从 Mongoid 2.0.0.rc7 迁移，现在当我保存我的模型实例时，我得到一个堆栈级别太深的异常，这在 rc7 上没有发生。
这是我的模型，非常简单：
class Firm
include Mongoid::Document
references_many :accounts, :autosave => true
end
class Account
include Mongoid::Document
field :name, :type => String
referenced_in :firm, :autosave => true
end
这是一些示例代码：
firm = Firm.create! :name=>'XYZ'
acc = Account.create! :name=>"Hello", :firm=>firm
抛出异常Account.create!
创建帐户会导致巨大的堆栈跟踪：
SystemStackError: stack level too deep
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_103'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_67'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_67'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_103'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_103'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_67'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_67'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_103'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_103'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_67'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_67'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_103'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_103'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_67'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_67'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_103'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_103'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_67'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_67'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_103'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_103'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_67'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_67'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_103'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_103'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_67'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_67'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:29:in `_callback_after_103'
org/jruby/RubyArray.java:1615:in `each'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/relations/auto_save.rb:28:in `_callback_after_103'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:429:in `_run_save_callbacks'
org/jruby/RubyBasicObject.java:1698:in `__send__'
org/jruby/RubyKernel.java:2097:in `send'
/home/x/.rvm/gems/jruby-1.6.7/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:93:in `run_callbacks'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/modification.rb:23:in `prepare'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence/operations/update.rb:43:in `persist'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:86:in `update'
/home/x/.rvm/gems/jruby-1.6.7/gems/mongoid-2.2.0/lib/mongoid/persistence.rb:151:in `upsert'
我只需要autosave在一个模型中定义吗？因为如果我这样做了，那似乎可行。我明白为什么在两个模型中都设置自动保存会导致无限循环，但正确的解决方案是什么？