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From "Yongjun Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6502) incorrect description in distcp2 document
Date Thu, 12 Jun 2014 16:26:07 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14029322#comment-14029322
] 

Yongjun Zhang commented on HDFS-6502:
-------------------------------------

HI [~ajisakaa],

I reviewed it and suggest a little more modification:

Original 
{quote}
-update` | Overwrite if src size different from dst size | As noted in the preceding, this
is not a "sync" operation. The only criterion examined is the source and destination file
sizes; if they differ, the source file replaces the destination file. As discussed in the
Usage documentation, it also changes the semantics for generating destination paths, so users
should use this carefully.
{quote}

Current patched version
{quote}
`-update` | Overwrite if source and destination have different contents | As noted in the
preceding, this is not a "sync" operation. The criteria examined are the source and destination
file sizes, blocksizes, and checksums; if they differ, the source file replaces the destination
file. As discussed in the Usage documentation, it also changes the semantics for generating
destination paths, so users should use this carefully.
{quote}

New suggested change:
{quote}
`-update` | Overwrite if source and destination differ in size, blocksize, or checksum | As
noted in the preceding, this is not a "sync" operation. The criteria examined are the source
and destination file sizes, blocksizes, and checksums; if they differ, the source file replaces
the destination file. As discussed in the Usage documentation, it also changes the semantics
for generating destination paths, so users should use this carefully.
{quote}

Thanks again for the patch.



> incorrect description in distcp2 document
> -----------------------------------------
>
>                 Key: HDFS-6502
>                 URL: https://issues.apache.org/jira/browse/HDFS-6502
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: documentation
>    Affects Versions: 1.2.1, 2.5.0
>            Reporter: Yongjun Zhang
>            Assignee: Akira AJISAKA
>              Labels: newbie
>         Attachments: HDFS-6502.patch
>
>
> In http://hadoop.apache.org/docs/r1.2.1/distcp2.html#UpdateAndOverwrite
> The first statement of the "Update and Overwrite" section says:
> {quote}
> -update is used to copy files from source that don't exist at the target, or have different
contents. -overwrite overwrites target-files even if they exist at the source, or have the
same contents.
> {quote}
> The "Command Line Options" table says :
> {quote}
>   -overwrite: Overwrite destination
>   -update: Overwrite if src size different from dst size
> {quote}
> Based on the implementation, making the following modification would be more accurate:
> The first statement of the "Update and Overwrite" section:
> {code}
> -update is used to copy files from source that don't exist at the target, or have different
contents. -overwrite overwrites target-files if they exist at the target.
> {code}
> The "Command Line Options" table:
> {code}
>   -overwrite: Overwrite destination
>   -update: Overwrite destination if source and destination have different contents
> {code}
> Thanks.



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