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 save(self, *args, **kwargs):
        # Get all other primary domains with the same tenant
        domain_list = self.__class__.objects.filter(tenant=self.tenant, is_primary=True).exclude(pk=self.pk)
        # If we have no primary domain yet, set as primary domain by default
        self.is_primary = self.is_primary or (not domain_list.exists())
        if self.is_primary:
            # Remove primary status of existing domains for tenant
            domain_list.update(is_primary=False)
        super().save(*args, **kwargs)