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https://issues.apache.org/jira/browse/HIVE-1723?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12922193#action_12922193
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Liyin Tang commented on HIVE-1723:
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The root cause of missing some part of join result is because the join value
for the small table is an empty array list (or multiple empty array list).
So everytime the jdbm will serialize the nothing on disk for this empty array
list.
Also the jdbm will read nothing from disk, which will cause the wrong result
problem.
Because it still need this empty array list when doing the join work.
> The result of left semi join is not correct
> -------------------------------------------
>
> Key: HIVE-1723
> URL: https://issues.apache.org/jira/browse/HIVE-1723
> Project: Hadoop Hive
> Issue Type: Bug
> Reporter: Liyin Tang
> Assignee: Liyin Tang
>
> In the test case semijoin.q, there is a query:
> select /*+ mapjoin(b) */ a.key from t3 a left semi join t1 b on a.key = b.key
> sort by a.key;
> I think this query will return a wrong result if table t1 is larger than
> 25000 different keys
> To be simple, I tried a very similar query:
> select /*+ mapjoin(b) */ a.key from test_semijoin a left semi join
> test_semijoin b on a.key = b.key sort by a.key;
> The table of test_semijoin is like
> 0 0
> 1 1
> 2 2
> 3 3
> 4 4
> 5 5
> ... ...
> ... ....
> 25000 25000
> 25001 25001
> ... ....
> ... ....
> 25999 25999
> 26000 26000
> So we can easily estimate the correct result of this query should be the same
> keys from table test_semijoin itsel.
> Actually, the result is only part of that: only from 0 to 24544.
> 0
> 1
> 2
> ..
> ..
> 24543
> 24544
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