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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "Hive/FAQ" by ZhengShao
Date Wed, 09 Dec 2009 03:30:59 GMT
Dear Wiki user,

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The "Hive/FAQ" page has been changed by ZhengShao.


   1. When running a JOIN query, I see out-of-memory errors.
       This is usually caused by the order of JOIN tables.  Instead of "FROM tableA a JOIN
tableB b ON ...", try "FROM tableB b JOIN tableA a ON ...". NOTE that if you are using LEFT
OUTER JOIN, you might want to change to RIGHT OUTER JOIN.  This trick usually solve the problem
- the rule of thumb is, always put the table with a lot of rows having the same value in the
join key on the rightmost side of the JOIN.
+  1. I am using MySQL as metastore and I see errors: "com.mysql.jdbc.exceptions.jdbc4.!CommunicationsException:
Communications link failure"
+      This is usually caused by MySQL servers closing connections after the connection is
idling for some time.  Run the following command on the MySQL server will solve the problem
"set global wait_status=120;"

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