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https://issues.apache.org/jira/browse/HADOOP-15209?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Steve Loughran updated HADOOP-15209:
------------------------------------
    Status: Patch Available  (was: Open)

Patch 006
checksum comparison changes reverted, though there's one optimisation: if 
source doesn't have a checksum, there's no probe for the endpoint. Saves 
HTTP/RPC calls when doing a distcp from an FS without checksums. 

Tested: s3a ireland, azure & adl UK. (this patch adds the azure one)



> 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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