Mihailo Aleksic created SPARK-52462:
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Summary: Enforce type coercion before children output
deduplication in Union
Key: SPARK-52462
URL: https://issues.apache.org/jira/browse/SPARK-52462
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 4.1.0
Reporter: Mihailo Aleksic
Right now, query the following query produces different plans between delta and
non-delta underlying tables. Query:
SELECT col1, col2, col3, NULLIF('','') AS col4
FROM table
UNION ALL
SELECT col2, col2, null AS col3, col4
FROM table;
This happens because of rule ordering:
- Using Delta table: ... -> WidenSetOperationTypes -> ... -> ResolveReferences
(deduplication of Union children outputs) -> ...
- Using non-Delta table: ... -> ResolveReferences (deduplication of Union
children outputs) -> ... -> WidenSetOperationTypes -> ...
In this issue I propose that we align those two by enforcing type coercion to
happen before deduplication.
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