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https://issues.apache.org/jira/browse/HADOOP-16083?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Siyao Meng updated HADOOP-16083:
--------------------------------
    Attachment: HADOOP-16083.001.patch
        Status: Patch Available  (was: Open)

> DistCp shouldn't always overwrite the target file when checksums match
> ----------------------------------------------------------------------
>
>                 Key: HADOOP-16083
>                 URL: https://issues.apache.org/jira/browse/HADOOP-16083
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: tools/distcp
>    Affects Versions: 3.1.1, 3.2.0, 3.3.0
>            Reporter: Siyao Meng
>            Assignee: Siyao Meng
>            Priority: Major
>         Attachments: HADOOP-16083.001.patch
>
>
> {code:java|title=CopyMapper#setup}
> ...
>     try {
>       overWrite = overWrite || 
> targetFS.getFileStatus(targetFinalPath).isFile();
>     } catch (FileNotFoundException ignored) {
>     }
> ...
> {code}
> The above code overrides config key "overWrite" to "true" when the target 
> path is a file. Therefore, unnecessary transfer happens when the source and 
> target file have the same checksums.
> My suggestion is: remove the code above. If the user insists to overwrite, 
> just add -overwrite in the options:
> {code:bash|title=DistCp command with -overwrite option}
> hadoop distcp -overwrite hdfs://localhost:64464/source/5/6.txt 
> hdfs://localhost:64464/target/5/6.txt
> {code}



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