ovr commented on a change in pull request #1660:
URL: https://github.com/apache/arrow-datafusion/pull/1660#discussion_r796034327
##########
File path: datafusion/src/physical_plan/unicode_expressions.rs
##########
@@ -457,21 +457,29 @@ pub fn substr<T: StringOffsetSizeTrait>(args:
&[ArrayRef]) -> Result<ArrayRef> {
start,
count
)))
- } else if start <= 0 {
- Ok(Some(string.to_string()))
} else {
let graphemes =
string.graphemes(true).collect::<Vec<&str>>();
- let start_pos = start as usize - 1;
- let count_usize = count as usize;
- if graphemes.len() < start_pos {
+ let (start_pos, end_pos) = if start <= 0 {
+ let end_pos = start + count - 1;
+ (
+ 0_usize,
+ if end_pos < 0 {
+ // we use 0 as workaround for usize to
return empty string
+ 0
+ } else {
+ end_pos as usize
+ },
Review comment:
@Jimexist It doesn't work because it doesn't reflect comparing with less
than 0. `-1 (i32)` with `as usize` will produce a maximum number that can be
stored in `usize`.
@alamb It doesnt work.
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