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https://issues.apache.org/jira/browse/HIVE-741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12896792#action_12896792
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Amareshwari Sriramadasu commented on HIVE-741:
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By adding logs to ExecReducer, I see that the input to reduce is the following:
{noformat}
{"key":{"joinkey0":null},"value":{"_col0":null,"_col1":35},"alias":0}
{"key":{"joinkey0":null},"value":{"_col0":12,"_col1":null},"alias":1}
{"key":{"joinkey0":10},"value":{"_col0":10,"_col1":1000},"alias":0}
{"key":{"joinkey0":10},"value":{"_col0":10,"_col1":100},"alias":0}
{"key":{"joinkey0":12},"value":{"_col0":12,"_col1":null},"alias":0}
{"key":{"joinkey0":35},"value":{"_col0":null,"_col1":35},"alias":1}
{"key":{"joinkey0":100},"value":{"_col0":100,"_col1":100},"alias":0}
{"key":{"joinkey0":100},"value":{"_col0":10,"_col1":100},"alias":1}
{"key":{"joinkey0":100},"value":{"_col0":100,"_col1":100},"alias":1}
{"key":{"joinkey0":1000},"value":{"_col0":10,"_col1":1000},"alias":1}
{noformat}
And joinkey with null values are processed under same group, I think they
should be processed in different groups, because comparison between nulls is
not defined.
> 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: Ning Zhang
>
> 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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