Dandandan commented on code in PR #16087:
URL: https://github.com/apache/datafusion/pull/16087#discussion_r2095061480
##########
datafusion/functions/src/string/ascii.rs:
##########
@@ -103,19 +106,29 @@ impl ScalarUDFImpl for AsciiFunc {
fn calculate_ascii<'a, V>(array: V) -> Result<ArrayRef, ArrowError>
where
- V: ArrayAccessor<Item = &'a str>,
+ V: StringArrayType<'a, Item = &'a str>,
{
- let iter = ArrayIter::new(array);
- let result = iter
- .map(|string| {
- string.map(|s| {
- let mut chars = s.chars();
- chars.next().map_or(0, |v| v as i32)
- })
- })
- .collect::<Int32Array>();
-
- Ok(Arc::new(result) as ArrayRef)
+ let mut values = Vec::with_capacity(array.len());
Review Comment:
Even faster should be (using `collect` rather than `push` and avoiding copy
by using `into`):
(Didn't compile the code, but it should look like this)
```
let values: Vec<_> = (0..array.len()).map(|i| {
if array.is_null(i) {
0
} else {
let s = array.value(i);
s.chars().next().map_or(0, |c| c as i32)
}
}).collect();
let array = Int32Array::new(values.into(), array.nulls().cloned());
Ok(Arc::new(array))
```
Futhermore, you can specialize for non-null arrays:
```
let values: Vec<_> =
match array.nulls().filter(|n| n.null_count > 0) {
Some(nulls) {
// existing code
},
None => {
// skip null check
(0..array.len()).map(|i| {
let s = array.value(i);
s.chars().next().map_or(0, |c| c as i32)
}
}).collect()
}
```
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