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https://issues.apache.org/jira/browse/HIVE-1194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12838113#action_12838113
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Namit Jain commented on HIVE-1194:
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Based on a offline discussion with Yongqiang, we were thinking of the following:
There will be a new mapping in MapredWork ->
Operator -> MapredLocalWork
This will be populated for SortMergeJoinOperator only.
SortMergeJoinOperator is a new operator which extends MapJoinOperator, and has
the
same name as a MapJoinOperator.
MapJoinProcessor needs to create a SortMergeJoinOperator instead of a
MapJoinOperator
when it sees the new configuration parameter.
MapJoinFactory methods need to change to create Operator->MapredLocalWork
instead of
MapredLocalWork in MapredWork.
> 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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