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https://issues.apache.org/jira/browse/HIVE-3430?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13448652#comment-13448652
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Namit Jain commented on HIVE-3430:
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Or a much simpler query:
explain
select b.value, b.cnt as cnt1, d.cnt as cnt2 from
(select a.value, count(1) as cnt from T1 a where a.ds='1' group by a.value) b
join
(select c.value, count(1) as cnt from T2 c where c.ds = '1' group by c.value)
d
on b.value = d.value;
The join needs a separate map-reduce job - it does not use the fact that the
group by has already distributed the data by join key.
> group by followed by join with the same key should be optimized
> ---------------------------------------------------------------
>
> Key: HIVE-3430
> URL: https://issues.apache.org/jira/browse/HIVE-3430
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Namit Jain
>
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