alamb commented on code in PR #19571:
URL: https://github.com/apache/datafusion/pull/19571#discussion_r2677488816
##########
datafusion/functions/src/unicode/left.rs:
##########
@@ -139,14 +139,23 @@ fn left_impl<'a, T: OffsetSizeTrait, V:
ArrayAccessor<Item = &'a str>>(
n_array: &Int64Array,
) -> Result<ArrayRef> {
let iter = ArrayIter::new(string_array);
+ let mut chars_buf = Vec::new();
let result = iter
.zip(n_array.iter())
.map(|(string, n)| match (string, n) {
(Some(string), Some(n)) => match n.cmp(&0) {
Ordering::Less => {
- let len = string.chars().count() as i64;
- Some(if n.abs() < len {
- string.chars().take((len + n) as
usize).collect::<String>()
+ // Collect chars once and reuse for both count and take
Review Comment:
You can probably use
https://doc.rust-lang.org/std/primitive.str.html#method.char_indices here to
avoid copying the strings into `chars_buf` entirely -- you could just find the
correct offset and then copy the relevant bytes
If you wanted to get super fancy, you could add specializations for:
1. Scalar `n` (no need to expand it out to an array)
2. StringViewArray (no need to copy strings at all, you could just adjust
the views)
However, this code seems better than what is on main! So we can merge it too
and keep iterating
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
