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https://issues.apache.org/jira/browse/HIVE-8920?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14236931#comment-14236931
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Chao commented on HIVE-8920:
----------------------------
Hi [~xuefuz], yes, the plan is correct (albeit a little bit confusing). The
problem is in {{SplitSparkWorkResolver#splitBaseWork}}, which doesn't handle
the case when the childWork is a UnionWork. Right now, it only handles the case
when childWork is a ReduceWork.
> SplitSparkWorkResolver doesn't work with UnionWork [Spark Branch]
> -----------------------------------------------------------------
>
> Key: HIVE-8920
> URL: https://issues.apache.org/jira/browse/HIVE-8920
> Project: Hive
> Issue Type: Sub-task
> Components: Spark
> Affects Versions: spark-branch
> Reporter: Chao
>
> The following query will not work:
> {code}
> from (select * from table0 union all select * from table1) s
> insert overwrite table table3 select s.x, count(1) group by s.x
> insert overwrite table table4 select s.y, count(1) group by s.y;
> {code}
> Currently, the plan for this query, before SplitSparkWorkResolver, looks like
> below:
> {noformat}
> M1 M2
> \ / \
> U3 R5
> |
> R4
> {noformat}
> In {{SplitSparkWorkResolver#splitBaseWork}}, it assumes that the
> {{childWork}} is a ReduceWork, but for this case, you can see that for M2 the
> childWork could be UnionWork U3. Thus, the code will fail.
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