gistfile1.js

// View function to get all users which have a specific room_id
// in their 'rooms' array.
function(doc) {
  if (doc.username) {
    for (var i = 0; i < doc.rooms.length; i++) {
      emit(doc.rooms[i], { avatar_url: doc.avatar_url, username: doc.username });
    }
  }
}

// Query with "GET /database/_design/users/_view/by_room?key=room_id