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https://issues.apache.org/jira/browse/HADOOP-15209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16390359#comment-16390359
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Steve Loughran commented on HADOOP-15209:
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checkstyle are on method length and a line being 84 vs 80. Needless

h1. Can someone start reviewing this so we can get it into Hadoop 3.1? 

thanks

> DistCp to eliminate needless deletion of files under already-deleted 
> directories
> --------------------------------------------------------------------------------
>
>                 Key: HADOOP-15209
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15209
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: tools/distcp
>    Affects Versions: 2.9.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>            Priority: Major
>         Attachments: HADOOP-15209-001.patch, HADOOP-15209-002.patch, 
> HADOOP-15209-003.patch, HADOOP-15209-004.patch, HADOOP-15209-005.patch, 
> HADOOP-15209-006.patch
>
>
> DistCP issues a delete(file) request even if is underneath an already deleted 
> directory. This generates needless load on filesystems/object stores, and, if 
> the store throttles delete, can dramatically slow down the delete operation.
> If the distcp delete operation can build a history of deleted directories, 
> then it will know when it does not need to issue those deletes.
> Care is needed here to make sure that whatever structure is created does not 
> overload the heap of the process.



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