HaoYang670 commented on code in PR #1832: URL: https://github.com/apache/arrow-rs/pull/1832#discussion_r894256202
########## arrow/src/compute/kernels/substring.rs: ########## @@ -182,24 +182,66 @@ pub fn substring_by_char<OffsetSize: OffsetSizeTrait>( start: i64, length: Option<u64>, ) -> Result<GenericStringArray<OffsetSize>> { - Ok(array - .iter() - .map(|val| { - val.map(|val| { - let char_count = val.chars().count(); - let start = if start >= 0 { - start.to_usize().unwrap().min(char_count) - } else { - char_count - (-start).to_usize().unwrap().min(char_count) - }; - let length = length.map_or(char_count - start, |length| { - length.to_usize().unwrap().min(char_count - start) - }); + let mut vals = BufferBuilder::<u8>::new(array.value_data().len()); Review Comment: This will always allocate more memory than we need, but it's no big deal. -- 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: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org