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https://issues.apache.org/jira/browse/LUCENE-6241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14318431#comment-14318431
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Michael McCandless commented on LUCENE-6241:
--------------------------------------------

bq. The user will get IOException if we don't do something, and the IOException 
will make it look like a lucene bug to them.

Well, I think that's OK?  The IOExc will specific abusing directory they had 
added to Lucene's index directory?  Plus I think we are talking about very few 
actual occurrences of this: it's abusers who also use RAMDir's copy ctor.

Maybe we should simply remove RAMDir's copy ctor?  That method seems 
abusive/trappy to me too!

> don't filter subdirectories in listAll()
> ----------------------------------------
>
>                 Key: LUCENE-6241
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6241
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Robert Muir
>         Attachments: LUCENE-6241.patch, LUCENE-6241.patch
>
>
> The issue is, today this means listAll() is always slow, sometimes MUCH 
> slower, because it must do the fstat()-equivalent of each file to check if 
> its a directory to filter it out.
> When i benchmarked this on a fast filesystem, doing all these filesystem 
> metadata calls only makes listAll() 2.6x slower, but on a non-ssd, slower 
> i/o, it can be more than 60x slower.
> Lucene doesn't make subdirectories, so hiding these for abuse cases just 
> makes real use cases slower.
> To add insult to injury, most code (e.g. all of lucene except for where 
> RAMDir copies from an FSDir) does not actually care if extraneous files are 
> directories or not.
> Finally it sucks the name is listAll() when it is doing anything but that.
> I really hate to add a method here to deal with this abusive stuff, but I'd 
> rather add isDirectory(String) for the rare code that wants to filter out, 
> than just let stuff always be slow.



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