viirya opened a new pull request, #19532:
URL: https://github.com/apache/datafusion/pull/19532
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## Rationale for this change
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## What changes are included in this PR?
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Add levenshtein_with_buffer() function that accepts a reusable cache buffer
to avoid allocating a new Vec<usize> for each distance calculation.
Changes:
- Added levenshtein_with_buffer() in datafusion-common that takes a mutable
Vec<usize> buffer parameter
- Updated levenshtein function to use the optimized version with a reusable
buffer across all rows
- Applied optimization to all data types: Utf8View, Utf8, and LargeUtf8
- Added benchmark to measure performance improvements
Optimization:
- Before: Allocated new Vec<usize> cache for every row
- After: Single Vec<usize> buffer reused across all rows
Benchmark Results:
- size=1024, str_len=8: 60.6 µs → 45.9 µs (24% faster)
- size=1024, str_len=32: 615.5 µs → 598.5 µs (3% faster)
- size=4096, str_len=8: 234.7 µs → 180.5 µs (23% faster)
- size=4096, str_len=32: 2.46 ms → 2.38 ms (3% faster)
The optimization shows significant improvements for shorter strings (23-24%)
where allocation overhead is more prominent relative to algorithm cost. For
longer strings, the O(m×n) algorithm complexity dominates, but still shows
measurable 3% improvement from eliminating per-row allocations.
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## Are there any user-facing changes?
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