Krisztian Kasa created CALCITE-6453:
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Summary: Simplify casts which are result of constant reduction
Key: CALCITE-6453
URL: https://issues.apache.org/jira/browse/CALCITE-6453
Project: Calcite
Issue Type: Improvement
Reporter: Krisztian Kasa
Assignee: Krisztian Kasa
RexSimplify transforms nullable cast expressions with a non-nullable literal
operand which type is different from the cast type to another cast expression
with a literal operand with the same type as the cast.
If simplify is called again using the result cast expression of the first
simplification we get a literal only as a result.
Example:
Initial expression
{code:java}
CAST(_UTF-16LE'2020-10-30':VARCHAR(2147483647) CHARACTER SET "UTF-16LE"):DATE
{code}
where the operand is non-nullable varchar and the result of the cast is
nullable date.
After the first simplify call we get
{code:java}
CAST(2020-10-30:DATE):DATE
{code}
where the operand type is non-nullable date and the cast type is nullable date.
https://github.com/apache/calcite/blob/8ab0b03326730aa2cc6b476b2cbd8f99799bdacb/core/src/main/java/org/apache/calcite/rex/RexSimplify.java#L2269-L2276
After the second simplify call we get
{code:java}
2020-10-30:DATE
{code}
where the literal type is non-nullable date
https://github.com/apache/calcite/blob/8ab0b03326730aa2cc6b476b2cbd8f99799bdacb/core/src/main/java/org/apache/calcite/rex/RexSimplify.java#L2195-L2196
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