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https://issues.apache.org/jira/browse/HIVE-1194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12838120#action_12838120
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Zheng Shao commented on HIVE-1194:
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Why does SortMergeJoinOperator extends MapJoinOperator?
It seems to me that SortMergeJoinOperator does NOTneed the
in-memory/disk-backed HashMap that MapJoinOperator has, correct?
> sorted merge join
> -----------------
>
> Key: HIVE-1194
> URL: https://issues.apache.org/jira/browse/HIVE-1194
> Project: Hadoop Hive
> Issue Type: New Feature
> Components: Query Processor
> Reporter: Namit Jain
> Assignee: He Yongqiang
> Fix For: 0.6.0
>
>
> If the input tables are sorted on the join key, and a mapjoin is being
> performed, it is useful to exploit the sorted properties of the table.
> This can lead to substantial cpu savings - this needs to work across bucketed
> map joins also.
> Since, sorted properties of a table are not enforced currently, a new
> parameter can be added to specify to use the sort-merge join.
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