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Posted to issues@arrow.apache.org by "Mike Seddon (Jira)" <ji...@apache.org> on 2021/01/21 20:40:00 UTC

[jira] [Created] (ARROW-11339) [Rust][DataFusion] length kernel does not correctly calculate character length

Mike Seddon created ARROW-11339:
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             Summary: [Rust][DataFusion] length kernel does not correctly calculate character length
                 Key: ARROW-11339
                 URL: https://issues.apache.org/jira/browse/ARROW-11339
             Project: Apache Arrow
          Issue Type: Bug
          Components: Rust - DataFusion
            Reporter: Mike Seddon
            Assignee: Mike Seddon


The current kernel works for simple characters as it appears to be assuming that 1 byte = 1 character. this is very fast but is not a safe assumption given Arrow strings are utf8. 

A simple example of failure is from the Postgres example where the current `length` implementation will calculate 5.

`char_length('josé') → 4`

The correct method seems to be via https://docs.rs/unicode-segmentation/1.2.1/unicode_segmentation/struct.Graphemes.html which I can implement in my work here: https://github.com/apache/arrow/pull/9243 and remove from kernel.



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