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From "Gunther Hagleitner (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-18201) Disable XPROD_EDGE for sq_count_check() created for scalar subqueries
Date Mon, 11 Dec 2017 21:59:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-18201?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16286636#comment-16286636
] 

Gunther Hagleitner commented on HIVE-18201:
-------------------------------------------

Hm. Actually I think it's more complicated than just total data transfer. Time taken to produce
the xprod needs to be factored in as well.

> Disable XPROD_EDGE for sq_count_check()  created for scalar subqueries
> ----------------------------------------------------------------------
>
>                 Key: HIVE-18201
>                 URL: https://issues.apache.org/jira/browse/HIVE-18201
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 3.0.0
>            Reporter: Nita Dembla
>         Attachments: query6.explain2.out
>
>
> sq_count_check()  will either return an error at runtime or a single row. In case of
query6, the subquery has avg() function that should return a single row. Attaching the explain.

> This does not need an x-prod, because it is not useful to shuffle the big table side
for a cross-product against 1 row.



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