*scratch*

ruby-1.9.2-p136 :001 > j = Job.last
ruby-1.9.2-p136 :002 > j.file_data.file.gridio.class
 => Mongo::GridIO 
ruby-1.9.2-p136 :003 > CSV.new(j.file_data.file.gridio)
NoMethodError: undefined method `pos' for #<GridIO _id: 4d5cbe235ef0dbcaf2000001>
	from /Users/rchristie/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/csv.rb:2011:in `init_separators'
	from /Users/rchristie/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/csv.rb:1570:in `initialize'
	from (irb):3:in `new'
	from (irb):3
	from /Users/rchristie/dev/cast/vendor/ruby/1.9.1/gems/railties-3.0.4/lib/rails/commands/console.rb:44:in `start'
	from /Users/rchristie/dev/cast/vendor/ruby/1.9.1/gems/railties-3.0.4/lib/rails/commands/console.rb:8:in `start'
	from /Users/rchristie/dev/cast/vendor/ruby/1.9.1/gems/railties-3.0.4/lib/rails/commands.rb:23:in `<top (required)>'
	from script/rails:6:in `require'
	from script/rails:6:in `<main>'
ruby-1.9.2-p136 :004 > 


# It looks like the deprecated API, GridStore, used to support the methods like eof?, pos, and rewind so that I could
# essentially stream the file from Mongo into some consumer of that stream. I haven't tried going back to the older
# version of the driver or implementing the needed methods yet. I was just trying to find some background on why 
# that API was deprecated. 

GridStore was deprecated because of certain strange semantics and incompatibility with the core GridFS API implemented by the current Grid class.

You should be able to used GridIO#read to stream an object. I'd be happy to add any other methods you need (like eof?). You can file a JIRA with what you need or submit a pull request.

Just created an issue for tracking:
http://jira.mongodb.org/browse/RUBY-240

Thanks. I'll put submit a pull request for the others.