def insertRuleset(self, ruleset, domain):
		'''增加一个robots.txt规则集'''
		cur = self.conn.cursor()
		cur.execute("SELECT did FROM Domains WHERE domain=?", (domain,))
		did = cur.fetchone()[0]
		cur.execute("INSERT INTO Rulesets VALUES (NULL,?,?)",(did, ruleset))
		# 写入到文件
		self.conn.commit()
def _update_dimension(
        self,
        size_diff,
        total_size,
        max_visible_size,
        dimension_request_property):
    if max_visible_size is None:
      is_max_visible_size_unlimited = True
    else:
      is_max_visible_size_unlimited = max_visible_size <= 0