def robotsrulesetOfDomain(self, domain):
		'''检查domain是否在数据库中,
			否 --> (False, None)
			是 --> (True, 数据库中存储的robots.txt内容)
		'''
		exist = False
		cur = self.conn.cursor()
		# 是否存在
		cur.execute("SELECT 1 FROM Domains WHERE domain=?", (domain,))
		if cur.fetchone() :
			exist = True
		# 存在的话,结果是什么
		cur.execute("SELECT rules FROM Domains,Rulesets "
			"WHERE domain=? AND Domains.did=Rulesets.did"
			,(domain,) )
		ruleset = cur.fetchone()
		return (exist, ruleset)
def refresh(self):
        """refreshes the Gtk.Liststore"""
        self.backendid_to_iter = {}
        self.liststore.clear()

        # Sort backends
        # 1, put default backend on top
        # 2, sort backends by human name
        backends = list(self.req.get_all_backends(disabled=True))
        backends = sorted(backends,
                          key=lambda backend: (not backend.is_default(),
                                               backend.get_human_name()))

        for backend in backends:
            self.add_backend(backend)
            self.on_backend_state_changed(None, backend.get_id())