session機能を使わない小さいaplを作ってて
オフするのどうやるんだろうと調べてたら
どうやら、2.3では遅延ロードするってことに
なってたらしい。
（うぇぶたま さんの和訳が見れなかったので原文を見てみた）
Ruby on Rails 2.3 Release Notes
5.5 Rack-based Lazy-loaded Sessions
A big change pushed the underpinnings of Action Controller session storage down to the Rack level. This involved a good deal of work in the code, though it should be completely transparent to your Rails applications (as a bonus, some icky patches around the old CGI session handler got removed). It’s still significant, though, for one simple reason: non-Rails Rack applications have access to the same session storage handlers (and therefore the same session) as your Rails applications. In addition, sessions are now lazy-loaded (in line with the loading improvements to the rest of the framework). This means that you no longer need to explicitly disable sessions if you don’t want them; just don’t refer to them and they won’t load.
要は
rackレベルでsession管理するようになったらしく
不要なときに、明示的にoffしなくてもよくなったってことらしい。
なるほどなるほど。
