Yaoxuan Wu created FLINK-41039:
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Summary: A projection on top of EXCEPT ALL or INTERSECT ALL is
pushed into both inputs and changes the result
Key: FLINK-41039
URL: https://issues.apache.org/jira/browse/FLINK-41039
Project: Flink
Issue Type: Bug
Components: Table SQL / Planner
Affects Versions: 2.3.0
Reporter: Yaoxuan Wu
{code:sql}
SELECT x, y FROM (VALUES (1, 10)) AS a(x, y)
EXCEPT ALL
SELECT x, y FROM (VALUES (2, 10)) AS b(x, y);
-- (1, 10) correct
SELECT y FROM (
SELECT x, y FROM (VALUES (1, 10)) AS a(x, y)
EXCEPT ALL
SELECT x, y FROM (VALUES (2, 10)) AS b(x, y));
-- expected: 10
-- actual: (no rows)
{code}
{{ProjectSetOpTransposeRule}} pushes the projection {{y}} into both inputs, so
the EXCEPT ALL is computed on {{y}} alone and the two rows cancel. The rule
only refuses distinct set operations, but pushing a projection is only safe for
UNION ALL. INTERSECT ALL is wrong in the same way (it returns rows that should
not match). Streaming mode is affected too.
Reproduces on 2.0.1, 2.2.1, 2.3.0 and master.
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