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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-10987) Provide an iterator-based listing API for FileSystem
Date Fri, 31 Oct 2014 15:28:34 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-10987?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14191942#comment-14191942
] 

Kihwal Lee commented on HADOOP-10987:
-------------------------------------

bq. The current code will blindly extract the path portion and call DFSClient#listPaths().
This is not correct. 
Actually checkPath() is done first, so it will blow up with {{IllegalArgumentException}}.
Still, it does not work with cross-filesystem symlink.

> Provide an iterator-based listing API for FileSystem
> ----------------------------------------------------
>
>                 Key: HADOOP-10987
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10987
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>         Attachments: HADOOP-10987.patch, HADOOP-10987.v2.patch, HADOOP-10987.v3.patch,
HADOOP-10987.v4.branch-2.patch, HADOOP-10987.v4.patch
>
>
> Iterator based listing methods already exist in {{FileContext}} for both simple listing
and listing with locations. However, {{FileSystem}} lacks the former.  From what I understand,
it wasn't added to {{FileSystem}} because it was believed to be phased out soon. Since {{FileSystem}}
is very well alive today and new features are getting added frequently, I propose adding an
iterator based {{listStatus}} method. As for the name of the new method, we can use the same
name used in {{FileContext}} : {{listStatusIterator()}}.
> It will be particularly useful when listing giant directories. Without this, the client
has to build up a huge data structure and hold it in memory. We've seen client JVMs running
out of memory because of this.
> Once this change is made, we can modify FsShell, etc. in followup jiras.



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