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https://issues.apache.org/jira/browse/HIVE-17726?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16195667#comment-16195667
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Zoltan Haindrich commented on HIVE-17726:
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Seems like this problem arises from the fact the {{exists}} is somewhere
translated into an {{inner}} join.
At least this seems to be the problem to me at this point:
https://github.com/apache/hive/blob/caf3330330c9c8c5fc922f3186ddeab4266b60bb/ql/src/java/org/apache/hadoop/hive/ql/parse/SemanticAnalyzer.java#L8873
I think the correct join type would be {{leftsemi}} for these cases.
> Using exists may lead to incorrect results
> ------------------------------------------
>
> Key: HIVE-17726
> URL: https://issues.apache.org/jira/browse/HIVE-17726
> Project: Hive
> Issue Type: Bug
> Affects Versions: 3.0.0
> Reporter: Zoltan Haindrich
>
> {code}
> drop table if exists tx1;
> create table tx1 (a integer,b integer);
> insert into tx1 values (1, 1),
> (1, 2),
> (1, 3);
> select count(*) as result,3 as expected from tx1 u
> where exists (select * from tx1 v where u.a=v.a and u.b <> v.b);
> select count(*) as result,3 as expected from tx1 u
> where exists (select * from tx1 v where u.a=v.a and u.b <> v.b limit 1);
> {code}
> current results are 6 and 2.
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