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https://issues.apache.org/jira/browse/DRILL-1335?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jinfeng Ni updated DRILL-1335:
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Attachment: 0001-DRILL-1335-Fix-merge-join-operator-when-compare-null.patch
> Merge Join incorrectly return unqualified rows when join key is null.
> ----------------------------------------------------------------------
>
> Key: DRILL-1335
> URL: https://issues.apache.org/jira/browse/DRILL-1335
> Project: Apache Drill
> Issue Type: Bug
> Reporter: Jinfeng Ni
> Assignee: DrillCommitter
> Attachments:
> 0001-DRILL-1335-Fix-merge-join-operator-when-compare-null.patch
>
>
> Drill's merge join operator incorrectly returns unqualified rows, when join
> key is null value. For example,
> alter session set `planner.enable_hashjoin` = false;
> // Q1
> select * from cp.`region.json` t1, cp.`region.json` t2 where t1.non_exist =
> t2.non_exist2 ;
> Q1 should return 0 rows, since both left and right side of join comparison
> are NULL values. But Drill will return 12100 rows.
> The cause of this problem is MergeJoin operator thinks a comparison between
> NULL and NULL is a qualified condition, and returns that pair of joining row.
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