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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