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https://issues.apache.org/jira/browse/HIVE-14246?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15380178#comment-15380178
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Gunther Hagleitner commented on HIVE-14246:
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+1
> 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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