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 _files(self):
        if self.isexact():
            return [f for f in self._m1.files() if self(f)]
        # If m1 is not an exact matcher, we can't easily figure out the set of
        # files, because its files() are not always files. For example, if
        # m1 is "path:dir" and m2 is "rootfileins:.", we don't
        # want to remove "dir" from the set even though it would match m2,
        # because the "dir" in m1 may not be a file.
        return self._m1.files()