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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'''
