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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "Hive/LanguageManual/Joins" by NamitJain
Date Wed, 31 Mar 2010 21:23:16 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

The "Hive/LanguageManual/Joins" page has been changed by NamitJain.
http://wiki.apache.org/hadoop/Hive/LanguageManual/Joins?action=diff&rev1=14&rev2=15

--------------------------------------------------

    SELECT /*+ MAPJOIN(b) */ a.key, a.value
    FROM a join b on a.key = b.key
  }}}
- will be done on the mapper only. Instead of fetching B completely for each mapper of A,
only the required buckets are fetched. For the query above, the mapper processing bucket 1
for A will only fetch bucket 1 of B
+ can be done on the mapper only. Instead of fetching B completely for each mapper of A, only
the required buckets are fetched. For the query above, the mapper processing bucket 1 for
A will only fetch bucket 1 of B.
+ It is not the default behavior, and is governed by the following parameter. '''set hive.optimize.bucketmapjoin
= true'''
  

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