viirya commented on code in PR #513:
URL: https://github.com/apache/datafusion-comet/pull/513#discussion_r1632159142
##########
core/src/execution/datafusion/expressions/scalar_funcs/chr.rs:
##########
@@ -94,15 +94,43 @@ impl ScalarUDFImpl for ChrFunc {
}
fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
- let array = args[0].clone();
- match array {
- ColumnarValue::Array(array) => {
- let array = chr(&[array])?;
- Ok(ColumnarValue::Array(array))
- }
- _ => {
- exec_err!("The first argument must be an array, but got:
{:?}", array)
- }
+ make_scalar_function(chr)(args)
+ }
+}
+
+/// The make_scalar_function function is a higher-order function that:
+/// - Takes a function inner designed to operate on arrays.
+/// - Wraps this function in a closure that can accept a mix of scalar and
array inputs.
+/// - Converts scalar inputs to arrays, calls the inner function, and then
converts the result back to a scalar if the original inputs were all scalars.
+///
+/// taken from datafusion utils
+
+fn make_scalar_function<F>(inner: F) -> impl Fn(&[ColumnarValue]) ->
Result<ColumnarValue>
Review Comment:
Hmm, as Spark `Chr` expression has only one argument. It is either a
`ColumnarValue::Array` or a `ColumnarValue::Scalar`. We don't need to make it
complicated like this.
We can do simply:
```rust
let array = args[0].clone();
match array {
ColumnarValue::Array(array) => {
let array = chr(&[array])?;
Ok(ColumnarValue::Array(array))
}
ColumnarValue::Scalar(Utf8(Some(_))) => {
let values = array.into_array(1);
let array = chr(&[array])?;
Ok(ColumnarValue::Scalar(Utf8(Some(array.value(0).to_string()))))
}
ColumnarValue::Scalar(Utf8(None)) => {
Ok(ColumnarValue::Scalar(Utf8(None)))
}
_ => {
...
}
```
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