def getall(self):
        try:
            spec = {'data': {'$exists': 1}}
            fields = {'_id': 0}
            sort = [('tid', 1)]
            cur = self.db.docs.find(spec, fields, sort=sort)
        except Exception as e:
            raise DatabaseException(e)
        return [Document(**row) for row in cur]
def split(root, minRight):
    if root is None:
        return None, None
    if root.key >= minRight:
        left, right = split(root.left, minRight)
        root.left = right
        root.update()
        return left, root
    else:
        left, right = split(root.right, minRight)
        root.right = left
        root.update()
        return root, right