To clarify for the downvoters, I'm talking about this in the context of CouchDB, which I believe was a fair assumption to make seeing as Damien Katz is one of the principle people involved and it was announced today at CouchConf.

In CouchDB, running a filter on top of view results is something you can only do in list functions or client side, so I am very curious to see how they incorporate this into CouchDB.