Mryange opened a new pull request, #63784:
URL: https://github.com/apache/doris/pull/63784
### What problem does this PR solve?
Issue Number: None
Related PR: None
Problem Summary:
This PR optimizes two hot BE string function families that spend significant
time on repeated buffer growth and high-overhead character lookup.
1. `repeat`
- Replace the old per-row append loop with a shared two-pass execution
path for both vector repeat counts and constant repeat counts.
- Precompute `res_offsets` and total output size before writing results.
- Write directly into `ColumnString::Chars` with
`StringOP::fast_repeat()`.
2. `trim_in` / `ltrim_in` / `rtrim_in`
- Reuse SIMD-assisted ASCII symbol search for small trim sets.
- Add reverse symbol search helpers for right trim.
- Use a fixed-size UTF-8 small-set lookup path for common cases while
preserving fallback paths for larger trim strings.
3. Coverage and observability
- Add a larger `repeat('a', 256)` correctness case.
- Add `find_symbols` unit coverage for empty ranges, embedded NUL bytes,
boundary lengths, and cross-check cases.
- Add old/new microbenchmarks for both repeat and trim paths.
### Benchmark results
Local Release benchmark results on this machine:
#### repeat
| Case | Old | New | Speedup |
| --- | ---: | ---: | ---: |
| RepeatVector 4096/16/8 | 86184 ns | 42878 ns | 2.01x |
| RepeatVector 4096/16/64 | 411330 ns | 146498 ns | 2.81x |
| RepeatVector 1024/128/16 | 84985 ns | 39620 ns | 2.15x |
| RepeatVector 4096/0/64 | 222362 ns | 7382 ns | 30.12x |
| RepeatConst 4096/16/8 | 127848 ns | 59495 ns | 2.15x |
| RepeatConst 4096/16/64 | 764912 ns | 205294 ns | 3.73x |
| RepeatConst 1024/128/16 | 158499 ns | 78090 ns | 2.03x |
| RepeatConst 4096/0/64 | 395137 ns | 7107 ns | 55.60x |
#### trim
| Case | Old | New | Speedup |
| --- | ---: | ---: | ---: |
| ASCII, 4 trim chars, 65536 rows | 2398.526 us | 997.839 us | 2.40x |
| ASCII, 8 trim chars, 65536 rows | 2452.269 us | 872.865 us | 2.81x |
| ASCII, no match, 65536 rows | 318.894 us | 309.079 us | 1.03x |
| UTF-8, 2 trim chars, 65536 rows | 7832.364 us | 6799.569 us | 1.15x |
Note:
The medium and large trim cases reproduced the expected improvement
direction on this machine. One small-input case (`BM_TrimInAscii/1024`) was
slightly slower at 0.81x, while the 4096-row and 65536-row cases remained
clearly faster.
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [ ] Regression test
- [ ] Unit Test
- [ ] Manual test (add detailed scripts or steps below)
- [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
- [ ] Previous test can cover this change.
- [ ] No code files have been changed.
- [ ] Other reason <!-- Add your reason? -->
- Behavior changed:
- [ ] No.
- [ ] Yes. <!-- Explain the behavior change -->
- Does this need documentation?
- [ ] No.
- [ ] Yes. <!-- Add document PR link here. eg:
https://github.com/apache/doris-website/pull/1214 -->
### Check List (For Reviewer who merge this PR)
- [ ] Confirm the release note
- [ ] Confirm test cases
- [ ] Confirm document
- [ ] Add branch pick label <!-- Add branch pick label that this PR should
merge into -->
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