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https://issues.apache.org/jira/browse/HIVE-12384?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15007254#comment-15007254
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Laljo John Pullokkaran commented on HIVE-12384:
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The counter argument is this:
We already have an operator that handles type casting in MR.
So why penalize MR?
> Union Operator may produce incorrect result on TEZ
> --------------------------------------------------
>
> Key: HIVE-12384
> URL: https://issues.apache.org/jira/browse/HIVE-12384
> Project: Hive
> Issue Type: Bug
> Components: Hive
> Affects Versions: 0.14.0, 1.0.0, 1.1.0, 1.0.1, 1.2.1
> Reporter: Laljo John Pullokkaran
> Assignee: Laljo John Pullokkaran
> Attachments: HIVE-12384.1.patch, HIVE-12384.2.patch,
> HIVE-12384.3.patch
>
>
> Union queries may produce incorrect result on TEZ.
> TEZ removes union op, thus might loose the implicit cast in union op.
> Reproduction test case:
> set hive.cbo.enable=false;
> set hive.execution.engine=tez;
> select (x/sum(x) over()) as y from(select cast(1 as decimal(10,0)) as x
> from (select * from src limit 2)s1 union all select cast(1 as decimal(10,0))
> x from (select * from src limit 2) s2 union all select '100000000' x from
> (select * from src limit 2) s3)u order by y;
> select (x/sum(x) over()) as y from(select cast(1 as decimal(10,0)) as x from
> (select * from src limit 2)s1 union all select cast(1 as decimal(10,0)) x
> from (select * from src limit 2) s2 union all select cast (null as string) x
> from (select * from src limit 2) s3)u order by y;
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