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Posted to github@datafusion.apache.org by "andygrove (via GitHub)" <gi...@apache.org> on 2026/07/21 15:01:02 UTC
[PR] perf: optimize left_right in datafusion-functions [datafusion]
andygrove opened a new pull request, #23762:
URL: https://github.com/apache/datafusion/pull/23762
> This PR was created by an LLM as a draft PR. I will mark it as ready for review after human review.
## Which issue does this PR close?
N/A — autonomous exploratory PR.
## Rationale for this change
Added an ASCII fast path to left_right_byte_length so left/right compute the n-th codepoint byte offset via O(1) arithmetic instead of a per-row char_indices() UTF-8 scan.
## What changes are included in this PR?
Added an ASCII fast path to left_right_byte_length so left/right compute the n-th codepoint byte offset via O(1) arithmetic instead of a per-row char_indices() UTF-8 scan.
## Are these changes tested?
Correctness: unit tests + seeded differential fuzz (bit-identical Arrow output vs `main`).
Benchmark (criterion):
- string_view short_result: 4.848% faster (base 56784ns -> cand 54031ns)
- string long_result: 38.098% faster (base 141926ns -> cand 87855ns)
- string_view long_result: 44.817% faster (base 94346ns -> cand 52063ns)
- string short_result: 13.184% faster (base 88532ns -> cand 76860ns)
- string_view short_result: 15.165% faster (base 57136ns -> cand 48472ns)
- string long_result: 39.278% faster (base 140969ns -> cand 85600ns)
- string_view long_result: 40.29% faster (base 81808ns -> cand 48847ns)
- string short_result: 14.369% faster (base 86809ns -> cand 74336ns)
Full criterion output:
```text
left/string short_result
time: [73.406 µs 73.726 µs 74.067 µs]
change: [−15.026% −14.369% −13.742%] (p = 0.00 < 0.05)
Performance has improved.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) low mild
left/string long_result time: [85.227 µs 85.519 µs 85.827 µs]
change: [−39.588% −39.278% −38.969%] (p = 0.00 < 0.05)
Performance has improved.
Found 3 outliers among 100 measurements (3.00%)
1 (1.00%) low mild
2 (2.00%) high mild
left/string_view short_result
time: [48.206 µs 48.411 µs 48.613 µs]
change: [−17.549% −15.165% −13.033%] (p = 0.00 < 0.05)
Performance has improved.
left/string_view long_result
time: [48.383 µs 48.691 µs 49.038 µs]
change: [−40.884% −40.290% −39.714%] (p = 0.00 < 0.05)
Performance has improved.
right/string short_result
time: [76.804 µs 76.986 µs 77.159 µs]
change: [−13.955% −13.184% −12.465%] (p = 0.00 < 0.05)
Performance has improved.
Found 6 outliers among 100 measurements (6.00%)
3 (3.00%) low severe
3 (3.00%) low mild
right/string long_result
time: [88.219 µs 88.597 µs 88.938 µs]
change: [−38.351% −38.098% −37.853%] (p = 0.00 < 0.05)
Performance has improved.
right/string_view short_result
time: [53.380 µs 53.545 µs 53.728 µs]
change: [−5.5061% −4.8482% −4.1872%] (p = 0.00 < 0.05)
Performance has improved.
Found 3 outliers among 100 measurements (3.00%)
3 (3.00%) high mild
right/string_view long_result
time: [52.049 µs 52.332 µs 52.633 µs]
change: [−45.883% −44.817% −43.850%] (p = 0.00 < 0.05)
Performance has improved.
Found 6 outliers among 100 measurements (6.00%)
6 (6.00%) high mild
```
## Are there any user-facing changes?
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Re: [PR] perf: optimize left_right in datafusion-functions [datafusion]
Posted by "comphead (via GitHub)" <gi...@apache.org>.
comphead merged PR #23762:
URL: https://github.com/apache/datafusion/pull/23762
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Re: [PR] perf: optimize left_right in datafusion-functions [datafusion]
Posted by "codecov-commenter (via GitHub)" <gi...@apache.org>.
codecov-commenter commented on PR #23762:
URL: https://github.com/apache/datafusion/pull/23762#issuecomment-5035902101
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:white_check_mark: All modified and coverable lines are covered by tests.
:white_check_mark: Project coverage is 80.71%. Comparing base ([`050046a`](https://app.codecov.io/gh/apache/datafusion/commit/050046a7f0c08d64d8dba9ebf0e3544cbda6cd38?dropdown=coverage&el=desc&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache)) to head ([`e7f98fa`](https://app.codecov.io/gh/apache/datafusion/commit/e7f98fa18e30b8db244c24520267bfe3b1732b1a?dropdown=coverage&el=desc&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache)).
<details><summary>Additional details and impacted files</summary>
```diff
@@ Coverage Diff @@
## main #23762 +/- ##
==========================================
- Coverage 80.71% 80.71% -0.01%
==========================================
Files 1089 1089
Lines 368750 368753 +3
Branches 368750 368753 +3
==========================================
- Hits 297631 297626 -5
- Misses 53375 53380 +5
- Partials 17744 17747 +3
```
</details>
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