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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-970) mapjoin should be disabled if the size is too large
Date Thu, 03 Dec 2009 21:30:20 GMT
mapjoin should be disabled if the size is too large

                 Key: HIVE-970
                 URL: https://issues.apache.org/jira/browse/HIVE-970
             Project: Hadoop Hive
          Issue Type: New Feature
          Components: Query Processor
            Reporter: Namit Jain

Based on a detailed discussion with Ning, we were thinking of the following.

Add a configurable parameter, which sets the limit on the usage of mapjoin.
Assume that only the following can increase the size of the table:

UDTF, Transforms, Union, Join

(Although UDF and UDAF can also increase the total size by increasing the size of the row,
that is not likely to happen in the common case).

So, the map join hint will only be honored if none of the above are present at the source
and the size of the table is less than the limit.

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