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 __init__(
        self,
        base,
        filename="",
        data=None,
        ignore_extras=False,
        ignore_installed=False,
        skip_unavailable=False
    ):
        """
        :param base: the dnf base
        :param filename: the filename to load the transaction from (conflicts with the 'data' argument)
        :param data: the dictionary to load the transaction from (conflicts with the 'filename' argument)
        :param ignore_extras: whether to ignore extra package pulled into the transaction
        :param ignore_installed: whether to ignore installed versions of packages
        :param skip_unavailable: whether to skip transaction packages that aren't available
        """

        self._base = base
        self._filename = filename
        self._ignore_installed = ignore_installed
        self._ignore_extras = ignore_extras
        self._skip_unavailable = skip_unavailable

        if not self._base.conf.strict:
            self._skip_unavailable = True

        self._nevra_cache = set()
        self._nevra_reason_cache = {}
        self._warnings = []

        if filename and data:
            raise ValueError(_("Conflicting TransactionReplay arguments have been specified: filename, data"))
        elif filename:
            self._load_from_file(filename)
        else:
            self._load_from_data(data)