Integer sequence ids in Mongo

sequence.rb

Mongoid.database.add_stored_function "sequence", <<-__
  function(name) {
    var ret = db.counters.findAndModify({ query: { _id: name}, update: { $inc : { next: 1}}, "new" :true, upsert: true});
    return ret.next;
  }
__

class Sequence
  include Mongoid::Fields::Serializable

  def deserialize(object)
    object.to_i
  end

  def serialize(object)
    Mongoid.master.eval("sequence('#{object}')").to_i
  end
end

class A
  include Mongoid::Document
  field :_id, :type => Sequence
end

A.create(:_id => "as")

Yeah we're talking another rewrite of the association code in order to make that happen, and it would definitely be slower since Mongoid would have to reiterate through all the new documents before the save of any single one to set all the ids and foreign keys instead of just setting the id when instantiated and setting the foreign key when a document is added to an association. I don't want us to start getting to AR speeds. :)

yes i can understand that. somewhat humorously i have actually had AR projects configured so that it assignes ids up front to make circular associations simpler ;-)

you know, top level ids and intra-document ids are not really the same thing.... i've considered before both having nice ids on top level docs and object_ids for intra-document relations...

in the end it is indeed very difficult to beat the overall tradoffs object_ids provide. lately i've just been slugging the top level namespace in my urls, for instance

/dojo4/posts/comments/$object_id

and that addresses the 80% rule pretty well.