[jira] [Commented] (HIVE-5095) Hive needs new operator walker for parallelization/optimization for tez

["Vikram Dixit K (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-5095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13749168#comment-13749168 ] 

Vikram Dixit K commented on HIVE-5095:
--------------------------------------

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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