Yuming Wang created IMPALA-10634:
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Summary: Removes outer join if it only has DISTINCT on streamed
side
Key: IMPALA-10634
URL: https://issues.apache.org/jira/browse/IMPALA-10634
Project: IMPALA
Issue Type: Improvement
Components: Backend
Reporter: Yuming Wang
Removes outer join if it only has DISTINCT on streamed side:
{code:sql}
CREATE TABLE t1(a int, b int);
CREATE TABLE t2(a int, b int);
SELECT DISTINCT t1.b FROM t1 LEFT JOIN t2 ON t1.a = t2.a;
{code}
We can rewrite {{SELECT DISTINCT b FROM t1 LEFT JOIN t2 ON t1.a = t2.a}} to
{{SELECT DISTINCT t1.b FROM t1}}.
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