Steve Loughran created HADOOP-13208:
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Summary: 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
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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