[CALCITE-6453] Simplify casts which are result of constant reduction

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.38.0
• Labels: pull-request-available
• Assignee: Krisztian Kasa
• Reporter: Krisztian Kasa
• Created: 02/Jul/24 11:39
• Updated: 17/Oct/24 22:41
• Resolved: 17/Oct/24 22:41

Description

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

CAST(_UTF-16LE'2020-10-30':VARCHAR(2147483647) CHARACTER SET "UTF-16LE"):DATE

where the operand is non-nullable varchar and the result of the cast is nullable date.
After the first simplify call we get

CAST(2020-10-30:DATE):DATE

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

2020-10-30:DATE

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

Issue Links

• links to: GitHub Pull Request #3840