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From "Adam Kramer (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-1466) Add NULL DEFINED AS to ROW FORMAT specification
Date Thu, 15 Jul 2010 02:30:50 GMT
Add NULL DEFINED AS to ROW FORMAT specification
-----------------------------------------------

                 Key: HIVE-1466
                 URL: https://issues.apache.org/jira/browse/HIVE-1466
             Project: Hadoop Hive
          Issue Type: Improvement
            Reporter: Adam Kramer


I just updated the Hive wiki to clarify what some would consider an oddity: When NULL values
are exported to a script via TRANSFORM, they are converted to the string "\N", and then when
the script's output is read, any cell that contains only \N is treated as a NULL value.

I believe that there are very VERY few reasons why anyone would need cells that contain only
a backslash and then a capital N to be distinguished from NULL cells, but for complete generality,
we should allow this.

The way to do that is probably by adding a specification in the ROW FORMAT for a table that
would allow any string to be treated as a NULL if it is the only string in a cell. Some may
prefer the empty string, others the word NULL in caps, etc. I vote for keeping \N as the default
because I am used to it, but also for allowing this to be customized.

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