a course of action that does not deliver any positive results
1997 - New Scientist - The next person looking for the same information has to go through the process all over again - even if 1000 people have already been up the same blind alleys.
as blind as a bat
having very bad eyesight – informal
This expression probably arose from the bat's nocturnal habits and its disorientated flutterings if disturbed by day. The poor eyesight of bats (and less frequently, moles) has been proverbial since the late 16th century.