andygrove opened a new pull request, #23589:
URL: https://github.com/apache/datafusion/pull/23589
> 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 a scalar from/to fast path to string `replace` that hoists a
memmem::Finder out of the per-row loop and skips materializing scalar args into
N-element arrays, avoiding per-row searcher construction for the common
replace(col,'lit','lit') pattern.
## What changes are included in this PR?
Added a scalar from/to fast path to string `replace` that hoists a
memmem::Finder out of the per-row loop and skips materializing scalar args into
N-element arrays, avoiding per-row searcher construction for the common
replace(col,'lit','lit') pattern.
## Are these changes tested?
Correctness: unit tests + seeded differential fuzz (bit-identical Arrow
output vs `main`).
Benchmark (criterion):
- replace_scalar from=_ab_ [size=8192, str_len=64]: 58.573% faster (base
226815ns -> cand 93963ns)
- replace_scalar from=_the_ [size=8192, str_len=16]: 30.039% faster (base
155601ns -> cand 108860ns)
- replace_scalar from=_ab_ [size=8192, str_len=32]: 50.571% faster (base
174020ns -> cand 86017ns)
- replace_scalar from=_ab_ [size=8192, str_len=16]: 10.673% faster (base
135489ns -> cand 121028ns)
- replace_scalar from=_the_ [size=8192, str_len=32]: 52.7% faster (base
184286ns -> cand 87167ns)
- replace_scalar from=_the_ [size=8192, str_len=64]: 60.147% faster (base
227922ns -> cand 90834ns)
Full criterion output:
```text
replace_scalar from="ab" [size=8192, str_len=16]
time: [120.76 µs 120.96 µs 121.15 µs]
change: [−10.856% −10.673% −10.491%] (p = 0.00 <
0.05)
Performance has improved.
Found 12 outliers among 100 measurements (12.00%)
12 (12.00%) low mild
replace_scalar from="the" [size=8192, str_len=16]
time: [108.51 µs 108.62 µs 108.73 µs]
change: [−30.131% −30.039% −29.950%] (p = 0.00 <
0.05)
Performance has improved.
Found 2 outliers among 100 measurements (2.00%)
2 (2.00%) low mild
replace_scalar from="ab" [size=8192, str_len=32]
time: [85.876 µs 85.955 µs 86.065 µs]
change: [−50.687% −50.571% −50.449%] (p = 0.00 <
0.05)
Performance has improved.
Found 4 outliers among 100 measurements (4.00%)
1 (1.00%) high mild
3 (3.00%) high severe
replace_scalar from="the" [size=8192, str_len=32]
time: [87.137 µs 87.175 µs 87.225 µs]
change: [−52.797% −52.700% −52.610%] (p = 0.00 <
0.05)
Performance has improved.
Found 5 outliers among 100 measurements (5.00%)
2 (2.00%) low severe
1 (1.00%) low mild
2 (2.00%) high severe
replace_scalar from="ab" [size=8192, str_len=64]
time: [93.795 µs 93.907 µs 94.016 µs]
change: [−58.641% −58.573% −58.502%] (p = 0.00 <
0.05)
Performance has improved.
Found 18 outliers among 100 measurements (18.00%)
4 (4.00%) low severe
5 (5.00%) low mild
4 (4.00%) high mild
5 (5.00%) high severe
replace_scalar from="the" [size=8192, str_len=64]
time: [90.843 µs 90.891 µs 90.957 µs]
change: [−60.277% −60.147% −60.021%] (p = 0.00 <
0.05)
Performance has improved.
Found 9 outliers among 100 measurements (9.00%)
2 (2.00%) low severe
3 (3.00%) low mild
2 (2.00%) high mild
2 (2.00%) high severe
```
## Are there any user-facing changes?
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