Question

I have a routine action that creates an comment object, where an answer has_many comments.

I am experiencing a weird bug that occasionally deletes the existing comments for an answer when a new comment is posted to that answer. The new comment gets deleted as well.

MongoHQ kindly directed me to this issue: https://github.com/mongoid/mongoid/issues/1173, but i am using mongoid2.2, which is supposed not to have this issue.

class Answer
  include Mongoid::Document
  has_many :comments, :dependent => :delete

class Comment
  include Mongoid::Document
  belongs_to :answer

---

# answer controller
def comment
  answer=Answer.find(params[:id])
  c=Comment.new(:text=>params[:text],:user_id=>current_user.id,:answer_id=>answer.id)
  success=c.save

  respond_to do |format|
    format.json {
        render :json=>c.to_json
      else
        render :json=>{"failure"=>c.errors}.to_json
      end
    }
  end    
end

More details included here:
http://pastie.org/2488895

Answer 1

I fixed it by downgrading to mongoid 2.0.2. This seems to be a very specific bug that only happens under a 1-N relationship, and if you are on mongohq. Hope it gets fixed in mongoid >2.2