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https://issues.apache.org/jira/browse/HIVE-1605?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12903584#action_12903584
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Ning Zhang commented on HIVE-1605:
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Came up with a patch along with some other performance improvement in
SMBMapJoinOperator. Still running tests.
> regression and improvements in handling NULLs in joins
> ------------------------------------------------------
>
> Key: HIVE-1605
> URL: https://issues.apache.org/jira/browse/HIVE-1605
> Project: Hadoop Hive
> Issue Type: Improvement
> Reporter: Ning Zhang
> Assignee: Ning Zhang
>
> There are regressions in sort-merge map join after HIVE-741. There are a lot
> of OOM exceptions in SMBMapJoinOperator. This caused by the HashMap
> maintained for each key to remember whether it is NULL. This takes too much
> memory when the tables are large.
> A second issu is in handling NULLs if the join keys are more than 1 column.
> This appears in regular MapJoin as well as SMBMapJoin. The code only checks
> if all the columns are NULL. It should return false in match if any joined
> value is NULL.
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