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Posted to mapreduce-dev@hadoop.apache.org by "mingran wang (JIRA)" <ji...@apache.org> on 2010/02/04 00:13:27 UTC

[jira] Created: (MAPREDUCE-1449) Sqoop Documentation about --split-by column has to be unique key seems to be wrong

Sqoop Documentation about --split-by column has to be unique key seems to be wrong
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                 Key: MAPREDUCE-1449
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1449
             Project: Hadoop Map/Reduce
          Issue Type: Bug
          Components: contrib/sqoop
    Affects Versions: 0.20.1
            Reporter: mingran wang


http://archive.cloudera.com/docs/sqoo... 

The document above shows that " To guarantee correctness of your input, you must select an ordering column for which each row has a unique value. If duplicate values appear in the ordering column, the results of the import are undefined, and Sqoop will not be able to detect the error." 

I read the source code for sqoop, it seems that the column to split by doesn't have to be a unique key. Plus, when the primary key is a composite key, the sqoop code only takes the first column of the composite key which in most cases is not unique key anyways. 

I also checked the output when non-unique key is used to split, there is nothing wrong with the result. 

I am wondering if the document is wrong, or there is some hidden trickiness that I am not aware of. 

I am using sqoop 20.1.

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[jira] Resolved: (MAPREDUCE-1449) Sqoop Documentation about --split-by column has to be unique key seems to be wrong

Posted by "Aaron Kimball (JIRA)" <ji...@apache.org>.
     [ https://issues.apache.org/jira/browse/MAPREDUCE-1449?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aaron Kimball resolved MAPREDUCE-1449.
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    Resolution: Won't Fix

Sqoop has been removed from MapReduce; issue moved to http://github.com/cloudera/sqoop/issues#issue/2

> Sqoop Documentation about --split-by column has to be unique key seems to be wrong
> ----------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1449
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1449
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: contrib/sqoop
>    Affects Versions: 0.20.1
>            Reporter: mingran wang
>
> http://archive.cloudera.com/docs/sqoo... 
> The document above shows that " To guarantee correctness of your input, you must select an ordering column for which each row has a unique value. If duplicate values appear in the ordering column, the results of the import are undefined, and Sqoop will not be able to detect the error." 
> I read the source code for sqoop, it seems that the column to split by doesn't have to be a unique key. Plus, when the primary key is a composite key, the sqoop code only takes the first column of the composite key which in most cases is not unique key anyways. 
> I also checked the output when non-unique key is used to split, there is nothing wrong with the result. 
> I am wondering if the document is wrong, or there is some hidden trickiness that I am not aware of. 
> I am using sqoop 20.1.

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