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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13371) S3A globber to use bulk listObject call over recursive directory scan
Date Sat, 18 Mar 2017 17:54:42 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15931307#comment-15931307
] 

ASF GitHub Bot commented on HADOOP-13371:
-----------------------------------------

Github user steveloughran commented on the issue:

    https://github.com/apache/hadoop/pull/203
  
    OK, I see what you've done here: hidden a filter in Path and then used it later on. I
like the trick
    
    At the same time, I think it's not going to get past anyone else: its making a fundamental
change to a core class, one that get serialized around and created a lot. It's not going to
be allowed.
    
    That's OK though, for the following reason: we have the freedom to add/extend the methods
in S3aFS itself, so can do one which takes a filter as a parameter. If we do it right, we
can get this into the FS spec, or at least start negotiating on that topic (needs: spec, tests,
etc), while implementing it in S3AFS without waiting.



> S3A globber to use bulk listObject call over recursive directory scan
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-13371
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13371
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs, fs/s3
>    Affects Versions: 2.8.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>
> HADOOP-13208 produces O(1) listing of directory trees in {{FileSystem.listStatus}} calls,
but doesn't do anything for {{FileSystem.globStatus()}}, which uses a completely different
codepath, one which does a selective recursive scan by pattern matching as it goes down, filtering
out those patterns which don't match. Cost is O(matching-directories) + cost of examining
the files.
> It should be possible to do the glob status listing in S3A not through the filtered treewalk,
but through a list + filter operation. This would be an O(files) lookup *before any filtering
took place*.



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