Method nullable

datafusion/physical-expr/src/expressions/cast.rs:235–244

(&self, input_schema: &Schema)

    }

    fn nullable(&self, input_schema: &Schema) -> Result<bool> {
        // A cast is nullable if **either** the child is nullable or the
        // target field allows nulls.  This conservative rule prevents
        // optimizers from assuming a non-null result when a null input could
        // still propagate.  `return_field()` continues to expose the exact
        // target metadata separately.
        let child_nullable = self.expr.nullable(input_schema)?;
        let target_nullable = self.resolved_target_field(input_schema)?.is_nullable();
        Ok(child_nullable || target_nullable)
    }

    fn evaluate(&self, batch: &RecordBatch) -> Result<ColumnarValue> {
        let value = self.expr.evaluate(batch)?;