def get_last_tid(self):
        try:
            spec = {'tid': {'$gt': 0}}
            sort = [('tid', -1)]
            row = self.db.docs.find_one(spec, sort=sort)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return row['tid']
        return 0
def setSAS(self, lenp3, ap2, lenp1):
        self.lenp3 = lenp3
        self.ap2 = ap2
        self.lenp1 = lenp1
        self.lenp2 = math.sqrt((self.lenp3 * self.lenp3 + self.lenp1 * self.lenp1) - 2* self.lenp3 * self.lenp1 * math.cos(self.ap2))
        #等於 SSS(AB, BC, CA)