theirix commented on code in PR #18032:
URL: https://github.com/apache/datafusion/pull/18032#discussion_r2495374021
##########
datafusion/functions/src/math/power.rs:
##########
@@ -91,58 +194,209 @@ impl ScalarUDFImpl for PowerFunc {
}
fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
- match arg_types[0] {
- DataType::Int64 => Ok(DataType::Int64),
- _ => Ok(DataType::Float64),
+ // Ok(arg_types[0].clone())
+ let [data_type, _] = take_function_args(self.name(), arg_types)?;
+ match data_type {
+ d if d.is_floating() => Ok(DataType::Float64),
+ d if d.is_integer() => Ok(DataType::Int64),
+ d if is_decimal(data_type) => Ok(d.clone()),
+ // DataType::Decimal32(p, s) => Ok(DataType::Decimal32(*p, *s)),
+ // DataType::Decimal64(p, s) => Ok(DataType::Decimal64(*p, 0)),
+ // DataType::Decimal128(p, s) => Ok(DataType::Decimal128(*p, 0)),
+ // DataType::Decimal256(p, s) => Ok(DataType::Decimal256(*p, 0)),
+ other => exec_err!(
+ "Unsupported data type {other:?} for {} function",
+ self.name()
+ ),
}
}
fn aliases(&self) -> &[String] {
&self.aliases
}
+ fn coerce_types(&self, arg_types: &[DataType]) -> Result<Vec<DataType>> {
Review Comment:
It's a good question. In the original code it was prevented at a signature
level, so the [evaluation
operated](https://github.com/apache/datafusion/blob/32d26187a358aaa0803867a7963cd149ec1fcd1e/datafusion/functions/src/math/power.rs#L118)
on allowed types only. However, when I tried to ban this int-to-float with new
coercion rules, the `scalar.slt` test failed, assuming we can do it (second
expression):
```sql
SELECT power(i32, exp_i) as power_i32,
power(i64, exp_f) as power_i64,
pow(f32, exp_i) as power_f32,
power(f64, exp_f) as power_f64,
pow(2, 3) as power_int_scalar,
power(2.5, 3.0) as power_float_scalar
FROM (select test.*, 3 as exp_i, 3.0 as exp_f from test) a
```
I am unsure if it worked before then.
With decimals, we allow float power only if it is convertible to int in
runtime (a focus of all these `pow_decimal_float` checks). Maybe we can apply
the same logic to the int-to-float.
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