martin-g commented on code in PR #19570:
URL: https://github.com/apache/datafusion/pull/19570#discussion_r2654838024
##########
datafusion/functions/src/string/split_part.rs:
##########
@@ -219,22 +219,22 @@ where
.try_for_each(|((string, delimiter), n)| -> Result<(),
DataFusionError> {
match (string, delimiter, n) {
(Some(string), Some(delimiter), Some(n)) => {
- let split_string: Vec<&str> =
string.split(delimiter).collect();
- let len = split_string.len();
-
- let index = match n.cmp(&0) {
- std::cmp::Ordering::Less => len as i64 + n,
+ let result = match n.cmp(&0) {
+ std::cmp::Ordering::Greater => {
+ // Positive index: use nth() to avoid collecting
all parts
+ // This stops iteration as soon as we find the nth
element
+ string.split(delimiter).nth((n - 1) as usize)
Review Comment:
Are 32-bit systems supported ?
`n` is Int64, so it is possible that this cast may lead to a truncation or
even a crash in debug build
##########
datafusion/functions/src/string/split_part.rs:
##########
@@ -219,22 +219,22 @@ where
.try_for_each(|((string, delimiter), n)| -> Result<(),
DataFusionError> {
match (string, delimiter, n) {
(Some(string), Some(delimiter), Some(n)) => {
- let split_string: Vec<&str> =
string.split(delimiter).collect();
- let len = split_string.len();
-
- let index = match n.cmp(&0) {
- std::cmp::Ordering::Less => len as i64 + n,
+ let result = match n.cmp(&0) {
+ std::cmp::Ordering::Greater => {
+ // Positive index: use nth() to avoid collecting
all parts
+ // This stops iteration as soon as we find the nth
element
+ string.split(delimiter).nth((n - 1) as usize)
+ }
+ std::cmp::Ordering::Less => {
+ // Negative index: use rsplit().nth() to
efficiently get from the end
+ // rsplit iterates in reverse, so -1 means first
from rsplit (index 0)
+ string.rsplit(delimiter).nth((-n - 1) as usize)
Review Comment:
another corner case: `-n` will fail for `i64::MIN`
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