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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "Hive/FAQ" by EricSammer
Date Wed, 06 Jan 2010 17:50:04 GMT
Dear Wiki user,

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


       To run a single clientnegative test alter1.q
         {{{ ant -Dtestcase=TestNegativeCliDriver -Dqfile=alter1.q test }}}
   1. How to change the warehouse.dir location for older tables?
       To change the base location of the Hive tables, edit the hive.metastore.warehouse.dir
       This will not affect the older tables. Metadata needs to be changed in the database
(MySQL or Derby). The location of Hive tables is in table SDS and column LOCATION.
@@ -13, +14 @@

   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;"
+  1. When using MySQL as a metastore I see the error "com.mysql.jdbc.exceptions.MySQLSyntaxErrorException:
Specified key was too long; max key length is 767 bytes".
+      This is a known limitation of MySQL 5.0 and UTF8 databases. One option is to use another
character set, such as 'latin1', which is known to work.

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