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 is_sql_dirty(sql):
    # This should not happen as using bytes in Python 3 is against db protocol,
    # but some people will pass it anyway
    if isinstance(sql, bytes):
        sql = sql.decode()
    # NOTE: not using regex here for speed
    sql = sql.lower()
    for action in ('update', 'insert', 'delete'):
        p = sql.find(action)
        if p == -1:
            continue
        start, end = p - 1, p + len(action)
        if (start < 0 or sql[start] not in CHARS) and (end >= len(sql) or sql[end] not in CHARS):
            return True
    else:
        return False