tlm365 commented on code in PR #14025:
URL: https://github.com/apache/datafusion/pull/14025#discussion_r1905501646
##########
datafusion/functions/src/unicode/reverse.rs:
##########
@@ -116,14 +115,23 @@ pub fn reverse<T: OffsetSizeTrait>(args: &[ArrayRef]) ->
Result<ArrayRef> {
}
}
-fn reverse_impl<'a, T: OffsetSizeTrait, V: ArrayAccessor<Item = &'a str>>(
+fn reverse_impl<'a, T: OffsetSizeTrait, V: StringArrayType<'a>>(
string_array: V,
) -> Result<ArrayRef> {
- let result = ArrayIter::new(string_array)
- .map(|string| string.map(|string: &str|
string.chars().rev().collect::<String>()))
- .collect::<GenericStringArray<T>>();
+ let mut builder: GenericStringBuilder<T> =
+ GenericStringBuilder::with_capacity(string_array.len(), 1024);
Review Comment:
> > I wonder if
[this](https://github.com/apache/arrow-rs/blob/4f1f6e57c568fae8233ab9da7d7c7acdaea4112a/arrow-array/src/array/mod.rs#L335-L338)
is a good alternative to `1024`? 🤔
>
> Yes, I think so
Unfortunately, it's a bit slower than the current implementation. It
allocates more mem than I expected, `string_array.get_array_memory_size()` =
`16632` when `str_len = 1024`, and = `66168` when `str_len = 4096` 🤔
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