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https://issues.apache.org/jira/browse/HADOOP-10987?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14109888#comment-14109888
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Colin Patrick McCabe commented on HADOOP-10987:
-----------------------------------------------
Nice idea.
{code}
+ public RemoteIterator<FileStatus> listStatusIterator(final Path p)
{code}
Can we put a comment in the base class that this implementation designed to be
overriden by filesystems that have a more efficient implementation?
{code}
+ @Override
+ public RemoteIterator<LocatedFileStatus> next(final FileSystem fs, final
Path p)
+ throws IOException {
+ if (fs instanceof DistributedFileSystem) {
+ return ((DistributedFileSystem)fs).listLocatedStatus(p, filter);
}
+ // symlink resolution for this methos does not work cross file systems
+ // because it is a protected method.
+ throw new IOException("Link resolution does not work with multiple " +
+ "file systems for listLocatedStatus(): " + p);
}
{code}
This is inconsistent with how all the other operations work. They do handle
cross-filesystem symlinks. There are two options for fixing it that I see:
1. Create a public method in FileSystem.java that calls the protected
two-argument form of listLocatedStatus.
2. Call the public one-argument form of listLocatedStatus and do the filtering
in DistributedFileSystem#listLocatedStatus.
> 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
>
>
> 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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