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From "Ning Zhang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-741) NULL is not handled correctly in join
Date Fri, 20 Aug 2010 04:20:16 GMT

    [ https://issues.apache.org/jira/browse/HIVE-741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12900570#action_12900570

Ning Zhang commented on HIVE-741:

Looks good in general. Some minor comments:
 1) add more test cases for SMB joins. Currently the only test case has only 1 bucket which
does not cover the most common use case. Can you add more test cases for more buckets? You
can take a look at bucketed join queries included in the client positive tests.
 2) SMBMapJoinOperator.compareKey() is called for each row so it is critical for performance.
In your code the hasNullElement() could be called 4 times in the worse case. If you cache
the result it can be called only twice. 

Yongqiang, any further comments?

> NULL is not handled correctly in join
> -------------------------------------
>                 Key: HIVE-741
>                 URL: https://issues.apache.org/jira/browse/HIVE-741
>             Project: Hadoop Hive
>          Issue Type: Bug
>            Reporter: Ning Zhang
>            Assignee: Amareshwari Sriramadasu
>         Attachments: patch-741-1.txt, patch-741-2.txt, patch-741.txt, smbjoin_nulls.q.txt
> With the following data in table input4_cb:
> Key        Value
> ------       --------
> NULL     325
> 18          NULL
> The following query:
> {code}
> select * from input4_cb a join input4_cb b on a.key = b.value;
> {code}
> returns the following result:
> NULL    325    18   NULL
> The correct result should be empty set.
> When 'null' is replaced by '' it works.

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