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https://issues.apache.org/jira/browse/HADOOP-13208?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Steve Loughran updated HADOOP-13208:
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    Attachment: HADOOP-13208-branch-2-019.patch

Patch 019


@Aaron

Returning the array directly; also renamed the param 'f' to 'path' for clarity.

@cnauroth

Why split the two iterators up? (i) to make it suspiciously close to 
java-8-lang lambdas and (ii) hopefully to line things up better for a high 
performance globber.

2. I've pushed the list call down into the `ObjectListingIterator` but left 
delimiter calculation to the caller.

3. FileStatusGenerator. I had a plan there to maybe generate liststatus values 
directly, but I'll postpone that plan & have inlined thaat code.

nits: all addressed



> S3A listFiles(recursive=true) to do a bulk listObjects instead of walking the 
> pseudo-tree of directories
> --------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-13208
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13208
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>    Affects Versions: 2.8.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>            Priority: Minor
>         Attachments: HADOOP-13208-branch-2-001.patch, 
> HADOOP-13208-branch-2-007.patch, HADOOP-13208-branch-2-008.patch, 
> HADOOP-13208-branch-2-009.patch, HADOOP-13208-branch-2-010.patch, 
> HADOOP-13208-branch-2-011.patch, HADOOP-13208-branch-2-012.patch, 
> HADOOP-13208-branch-2-017.patch, HADOOP-13208-branch-2-018.patch, 
> HADOOP-13208-branch-2-019.patch
>
>   Original Estimate: 24h
>  Remaining Estimate: 24h
>
> A major cost in split calculation against object stores turns out be listing 
> the directory tree itself. That's because against S3, it takes S3A two HEADs 
> and two lists to list the content of any directory path (2 HEADs + 1 list for 
> getFileStatus(); the next list to query the contents).
> Listing a directory could be improved slightly by combining the final two 
> listings. However, a listing of a directory tree will still be 
> O(directories). In contrast, a recursive {{listFiles()}} operation should be 
> implementable by a bulk listing of all descendant paths; one List operation 
> per thousand descendants. 
> As the result of this call is an iterator, the ongoing listing can be 
> implemented within the iterator itself



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