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From "Gopal V (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HIVE-14246) Tez: disable auto-reducer parallelism when CUSTOM_EDGE is in place
Date Fri, 15 Jul 2016 07:21:20 GMT

    [ https://issues.apache.org/jira/browse/HIVE-14246?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15378948#comment-15378948
] 

Gopal V edited comment on HIVE-14246 at 7/15/16 7:21 AM:
---------------------------------------------------------

"inconsistency of perf" unfortunately means some good runs too :)


was (Author: gopalv):
"inconsistency of perf" unfortunately means some god runs too :)

> Tez: disable auto-reducer parallelism when CUSTOM_EDGE is in place
> ------------------------------------------------------------------
>
>                 Key: HIVE-14246
>                 URL: https://issues.apache.org/jira/browse/HIVE-14246
>             Project: Hive
>          Issue Type: Bug
>          Components: Tez
>    Affects Versions: 2.2.0
>            Reporter: Gopal V
>            Assignee: Gopal V
>            Priority: Minor
>             Fix For: 2.2.0
>
>         Attachments: HIVE-14246.1.patch
>
>
> The CUSTOM_SIMPLE_EDGE impl has differences between the size constraints of either edge
which cannot be represented by the ShuffleVertexManager presently.
> Reducing the width based on the hashtable build side vs the streaming probe side have
different consequences since there is no order of runtime between them.
> Until the two parent vertices of the shuffle hash-join are related, this feature causes
massive inconsistency of performance across runs.
> For inner & semi joins, the hashtable side should have a higher priority than the
streaming side and for left outer joins, the streaming side can over-take the hashtable side,
being the more dominant factor in the final row-counts.
> Until such priorities can be bubbled up into ShuffleVertexManager, this feature can be
disabled.



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