neilconway opened a new pull request, #26377:
URL: https://github.com/apache/datafusion/pull/26377
## Which issue does this PR close?
- N/A
## Rationale for this change
#26192 switched `upper` for non-ASCII `Utf8View` inputs from using
`std::to_uppercase` to doing a per-character loop. While that change avoids an
allocation, it regresses inputs that have some ASCII-only bytes, because
`std::to_uppercase` has a special-case for that situation. For example, `upper`
on a `Utf8View` array with a single non-ASCII string was 19x slower.
This PR reverts that change, but in the course of doing so, we also add
several related optimizations to `upper`, `lower`, and the optimized string
builders; details below.
Benchmarks: (x86, AMD EPYC Milan)
upper
- Some non-ASCII rows:
- Utf8View, 4096 rows: 952.7 µs → 254.5 µs (−73.3%)
- Utf8View, 4096 rows, 10% nulls: 881.7 µs → 270.6 µs (−69.3%)
- Utf8View, 8192 rows: 1.94 ms → 539.7 µs (−72.2%)
- Utf8View, 8192 rows, 10% nulls: 1.79 ms → 559.4 µs (−68.7%)
- Non-ASCII words:
- Utf8: 825.5 µs → 726.6 µs (−12.0%)
- LargeUtf8: 824.7 µs → 726.3 µs (−11.9%)
- Utf8View: 759.5 µs → 727.6 µs (−4.2%)
- Mostly ASCII:
- Utf8, len 8: 204.0 µs → 19.6 µs (−90.4%)
- Utf8View, len 8: 214.6 µs → 36.5 µs (−83.0%)
- Utf8, len 32: 789.6 µs → 23.2 µs (−97.1%)
- Utf8View, len 32: 757.4 µs → 36.2 µs (−95.2%)
- Utf8, len 128: 3.13 ms → 51.7 µs (−98.3%)
- Utf8View, len 128: 2.89 ms → 47.5 µs (−98.4%)
- Late non-ASCII:
- Utf8, len 8: 268.2 µs → 154.1 µs (−42.5%)
- Utf8View, len 8: 259.4 µs → 156.5 µs (−39.7%)
- Utf8, len 32: 881.8 µs → 136.4 µs (−84.5%)
- Utf8View, len 32: 798.5 µs → 138.1 µs (−82.7%)
- Utf8, len 128: 3.20 ms → 164.5 µs (−94.9%)
- Utf8View, len 128: 2.95 ms → 163.9 µs (−94.4%)
lower
- Some non-ASCII rows:
- Utf8View, 4096 rows: 270.3 µs → 232.8 µs (−13.9%)
- Utf8View, 4096 rows, 10% nulls: 271.0 µs → 235.8 µs (−13.0%)
- Utf8View, 8192 rows: 568.8 µs → 495.8 µs (−12.8%)
- Utf8View, 8192 rows, 10% nulls: 572.5 µs → 502.4 µs (−12.3%)
- Non-ASCII words:
- Utf8: 514.2 µs → 511.0 µs (−0.6%)
- LargeUtf8: 507.8 µs → 516.4 µs (+1.7%)
- Utf8View: 510.2 µs → 509.4 µs (−0.2%)
- Mostly ASCII:
- Utf8, len 8: 67.8 µs → 18.6 µs (−72.5%)
- Utf8View, len 8: 73.9 µs → 36.5 µs (−50.7%)
- Utf8, len 32: 60.5 µs → 22.9 µs (−62.2%)
- Utf8View, len 32: 68.4 µs → 36.5 µs (−46.6%)
- Utf8, len 128: 76.7 µs → 52.1 µs (−32.1%)
- Utf8View, len 128: 82.6 µs → 46.8 µs (−43.3%)
- Late non-ASCII:
- Utf8, len 8: 136.9 µs → 138.8 µs (+1.4%)
- Utf8View, len 8: 140.0 µs → 139.8 µs (−0.1%)
- Utf8, len 32: 115.3 µs → 124.8 µs (+8.2%)
- Utf8View, len 32: 117.4 µs → 125.5 µs (+6.9%)
- Utf8, len 128: 138.9 µs → 150.0 µs (+8.0%)
- Utf8View, len 128: 142.4 µs → 152.3 µs (+7.0%)
translate (ASCII scalar from/to, no deletions)
- Utf8:
- 1024 rows, len 8: 10.1 µs → 9.1 µs (−9.8%)
- 1024 rows, len 32: 17.9 µs → 15.9 µs (−11.2%)
- 1024 rows, len 128: 48.8 µs → 39.2 µs (−19.6%)
- 1024 rows, len 1024: 363.8 µs → 270.7 µs (−25.6%)
- 4096 rows, len 8: 37.5 µs → 33.7 µs (−10.1%)
- 4096 rows, len 32: 68.6 µs → 62.8 µs (−8.5%)
- 4096 rows, len 128: 195.8 µs → 154.6 µs (−21.1%)
- 4096 rows, len 1024: 1.42 ms → 1.07 ms (−24.7%)
- Utf8View:
- 1024 rows, len 8: 9.1 µs → 8.4 µs (−8.2%)
- 1024 rows, len 32: 14.5 µs → 13.8 µs (−4.6%)
- 1024 rows, len 128: 36.2 µs → 35.0 µs (−3.3%)
- 1024 rows, len 1024: 236.2 µs → 235.4 µs (−0.3%)
- 4096 rows, len 8: 34.4 µs → 31.1 µs (−9.5%)
- 4096 rows, len 32: 55.4 µs → 52.5 µs (−5.2%)
- 4096 rows, len 128: 142.2 µs → 137.0 µs (−3.7%)
- 4096 rows, len 1024: 937.7 µs → 940.8 µs (+0.3%)
replace (single ASCII byte, Utf8)
- 1024 rows, len 32: 26.2 µs → 9.0 µs (−65.6%)
- 1024 rows, len 128: 92.6 µs → 16.4 µs (−82.3%)
- 1024 rows, len 32, 20% nulls: 22.8 µs → 9.1 µs (−60.3%)
- 1024 rows, len 128, 20% nulls: 76.5 µs → 14.6 µs (−80.9%)
- 4096 rows, len 32: 103.2 µs → 31.2 µs (−69.7%)
- 4096 rows, len 128: 372.6 µs → 61.9 µs (−83.4%)
- 4096 rows, len 32, 20% nulls: 89.9 µs → 33.5 µs (−62.7%)
- 4096 rows, len 128, 20% nulls: 316.5 µs → 56.8 µs (−82.1%)
## What changes are included in this PR?
* Add `StringViewArrayBuilder::try_append_byte_map`, a fallible variant of
the existing `append_byte_map`. (We need this to avoid regressing error
handling behavior on overflow when we use this method below.)
* `lower`, `upper`, for non-ASCII input arrays: we now check if each row is
ASCII. If it is, we construct the result value directly via the string
builder's `try_append_byte_map` method, which vectorizes. Non-ASCII rows are
converted via `std::to_uppercase / std::to_lowercase`.
* Optimize `GenericStringArrayBuilder::try_append_byte_map` to avoid calling
Arrow's `MutableBuffer::extend`, which is slow. Since we know exactly how many
bytes will be appended, we reserve that space in the value buffer first and
then do the per-byte map. This speeds up the callers of `try_append_byte_map`,
which include `translate` and `replace`.
* Comment cleanups / improvements
* Test consolidation: remove redundant tests, move more tests to SLT,
improve test coverage
* Benchmark consolidation: move `upper` and `lower` benchmarks to the same
place, add benchmarks for `upper` and `lower` on mixed ASCII and non-ASCII
inputs, add benchmark for `translate` on `Utf8View`
## What is the testing strategy for this PR?
Existing tests pass; new tests added.
## Are there any user-facing changes?
No.
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