perf: optimize left_right in datafusion-functions

[andygrove]

Which issue does this PR close?

N/A

Rationale for this change

Optimize existing expression.

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?

Existing tests.

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:

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?

No

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.71%. Comparing base (050046a) to head (e7f98fa).

Additional details and impacted files

@@            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     

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[getChan]

is_ascii() is very fast here thanks to std's SIMD/word-at-a-time checks. LGTM

[comphead]

Thanks @andygrove makes sense to me!