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https://issues.apache.org/jira/browse/HIVE-14027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15346927#comment-15346927
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Thejas M Nair commented on HIVE-14027:
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This is happening only when UDF is in picture. If it is a select without UDF,
the results are correct.
Some more experiments I ran with hive 1.2.1 -
created a new table - tbl2
hive> select * from tbl2;
OK
2 two
ran -
select a.n, a.t, concat(b.n, ""), concat(b.t, "") from (select * from tbl where
n = 1) a left outer join (select * from tbl2 where 1 = 2) b on a.n = b.n;
actually ran - select a.n, a.t, concat(b.n, ""), concat(b.t, "") from (select *
from tbl where n = 1) a left outer join (select * from tbl2 where 1 = 2) b on
a.n = b.n;
ie replaced tbl with tbl2 for b in original query.
it gives -
1 one 1 NULL
looks like the join key is getting used as the input
ie . a.t is getting used as input
sorry, a.n is getting used as input to concat(b.n, "")
there might be an assumption somewhere that a.n and b.n are the same, since
this is a join
but doesn't hold true for outer join
> NULL values produced by left outer join do not behave as NULL
> -------------------------------------------------------------
>
> Key: HIVE-14027
> URL: https://issues.apache.org/jira/browse/HIVE-14027
> Project: Hive
> Issue Type: Bug
> Components: Query Processor
> Affects Versions: 1.2.1, 2.0.1
> Reporter: Vaibhav Gumashta
> Assignee: Vaibhav Gumashta
>
> Consider the following setup:
> {code}
> create table tbl (n bigint, t string);
> insert into tbl values (1, 'one');
> insert into tbl values(2, 'two');
> select a.n, a.t, isnull(b.n), isnull(b.t) from (select * from tbl where n =
> 1) a left outer join (select * from tbl where 1 = 2) b on a.n = b.n;
> 1 one false true
> {code}
> The query should return true for isnull(b.n).
> I've tested by inserting a row with null value for the bigint column into
> tbl, and isnull returns true in that case.
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