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https://issues.apache.org/jira/browse/HIVE-5095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13749168#comment-13749168
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Vikram Dixit K commented on HIVE-5095:
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RB request.
https://reviews.apache.org/r/13787/
> Hive needs new operator walker for parallelization/optimization for tez
> -----------------------------------------------------------------------
>
> Key: HIVE-5095
> URL: https://issues.apache.org/jira/browse/HIVE-5095
> Project: Hive
> Issue Type: Bug
> Components: Tez
> Affects Versions: tez-branch
> Reporter: Vikram Dixit K
> Assignee: Vikram Dixit K
> Fix For: tez-branch
>
> Attachments: HIVE-5095.WIP.patch.txt
>
>
> For tez to compute the number of reducers, we should be walking the operator
> tree in a topological fashion so that the reducers down the tree get the
> estimate from all parents. However, the current walkers in hive only walk the
> operator tree in a depth-first fashion. We need to add a new walker for the
> topological walk. Also, since information about the parent operators needs to
> be propagated on a per parent basis, we need to retain some context across
> operators to be passed to the child which the walker will co-ordinate.
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