Jinfeng Ni created DRILL-1335:
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Summary: 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: Jinfeng Ni
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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