[jira] [Created] (IMPALA-10635) Removes outer join if it only has DISTINCT on streamed side

["Yuming Wang (Jira)" <ji...@apache.org>]

Yuming Wang created IMPALA-10635:
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             Summary: Removes outer join if it only has DISTINCT on streamed side
                 Key: IMPALA-10635
                 URL: https://issues.apache.org/jira/browse/IMPALA-10635
             Project: IMPALA
          Issue Type: Improvement
          Components: Backend
            Reporter: Yuming Wang


Removes outer join if it only has DISTINCT on streamed side. For example:
{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 t1.b FROM t1 LEFT JOIN t2 ON t1.a = t2.a}} to {{SELECT DISTINCT t1.b FROM t1}}.




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