[
https://issues.apache.org/jira/browse/HIVE-20867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16675550#comment-16675550
]
Pengcheng Xiong commented on HIVE-20867:
----------------------------------------
I have some questions about this jira. Could you share your design document on
this? I assumed that we compared several candidates when we made the decision,
and lefts semi join was one of them. We chose union-based one because a) a
similar approach can be applied to except(all) as well, thus we have better
code reuse. b) when we have more then 2 branches as the inputs of intersect, we
assume that in the future those branches can be executed in parallel. Comparing
with left-semi join one, we need to do the join one by one.
> Rewrite INTERSECT into LEFT SEMI JOIN instead of UNION + Group by
> -----------------------------------------------------------------
>
> Key: HIVE-20867
> URL: https://issues.apache.org/jira/browse/HIVE-20867
> Project: Hive
> Issue Type: Improvement
> Components: Query Planning
> Affects Versions: 4.0.0
> Reporter: Vineet Garg
> Assignee: Vineet Garg
> Priority: Major
>
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
