Github user steveloughran commented on the issue:
https://github.com/apache/spark/pull/14038
There's no performance problem from filtering just on names. It's when
people try to filter on more complex things (file type, timestamp) they need to
call `getFileStatus(path)` and that's the performance problem.
I've been through Spark looking at where anything like that is being done,
and have a patch to fix it....i don't want to have to do the same thing again
in future; something we can avoid by having a richer filter which passes the
`FileStatus` generated in the listing process.
Now, you may think "why doesn't Hadoop's list/glob operations take a richer
predicate?". That I can't answer, it's history is lost in the oldest bits of
the code.
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