joroKr21 commented on code in PR #12922:
URL: https://github.com/apache/datafusion/pull/12922#discussion_r1801484804
##########
datafusion/functions/src/macros.rs:
##########
@@ -226,9 +226,8 @@ macro_rules! make_math_unary_udf {
$EVALUATE_BOUNDS(inputs)
}
- fn invoke(&self, args: &[ColumnarValue]) ->
Result<ColumnarValue> {
- let args = ColumnarValue::values_to_arrays(args)?;
-
+ fn invoke(&self, col_args: &[ColumnarValue]) ->
Result<ColumnarValue> {
Review Comment:
Well simply the issue is that I don't know what is the batch size expected
to return from this function. Usually it's inferred by any of the argument's
length. But if all arguments are scalar values, then I can return a scalar
value and all is well. This works for immutable functions but not for volatile
ones. See e.g.
```rust
impl ScalarUDFImpl for RandomFunc {
fn as_any(&self) -> &dyn Any {
self
}
fn name(&self) -> &str {
"random"
}
fn signature(&self) -> &Signature {
&self.signature
}
fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
Ok(Float64)
}
fn invoke(&self, _args: &[ColumnarValue]) -> Result<ColumnarValue> {
not_impl_err!("{} function does not accept arguments", self.name())
}
fn invoke_no_args(&self, num_rows: usize) -> Result<ColumnarValue> {
let mut rng = thread_rng();
let mut values = vec![0.0; num_rows];
// Equivalent to set each element with rng.gen_range(0.0..1.0), but
more efficient
rng.fill(&mut values[..]);
let array = Float64Array::from(values);
Ok(ColumnarValue::Array(Arc::new(array)))
}
}
```
What if I wanted to implement `RandomFunc` with an upper bound? I can't use
`invoke_no_args` because I have one argument and I can't use `invoke` because
it doesn't tell me how many rows I should produce.
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