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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-18201) Disable XPROD_EDGE for sq_count_check() created for scalar subqueries
Date Tue, 05 Dec 2017 01:21:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-18201?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16277861#comment-16277861
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Ashutosh Chauhan commented on HIVE-18201:
-----------------------------------------

[~ndembla] I assume you are suggesting that instead of xprod_edge it should have been a broadcast
edge. 
I see in explain plan for both Reducer 10 and Reducer 14 which has xprod edges data size is
way too small so it should have selected broadcast edge at time of join  algo selection. Then,
CrossProductHandler has a logic to replace edges of type only Simple and Custom Simple, so
not sure why we get XPROD edges there. [~aplusplus] do you know why we still got XPROD here?


> 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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