[SPARK-59062][CORE] Word-at-a-time single-byte search for UTF8String.contains - #58354
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…contains `UTF8String.contains` scans byte-by-byte. For a single-byte needle -- the common case produced by `LIKE '%x%'` (rewritten to `Contains`) with an ASCII character -- add a word-at-a-time (SWAR / memchr-style) scan that checks 8 bytes per iteration. Add `ByteArrayMethods.containsByte(base, offset, length, target)`, which XORs each 8-byte word with the broadcast target byte and uses the exact "word contains a zero byte" test `(w - 0x0101010101010101L) & ~w & 0x8080808080808080L`. It reports only existence (not position), so it is endianness independent; alignment handling mirrors `arrayEquals`. `UTF8String.contains` takes a `numBytes == 1` fast path that delegates to it, which also drops the redundant per-position `matchAt` call.
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What changes were proposed in this pull request?
UTF8String.containsscans for the needle byte-by-byte. For a single-byte needle --the common case produced by
LIKE '%x%'(which the optimizer rewrites toContains) withan ASCII character -- this PR adds a word-at-a-time (SWAR / memchr-style) scan.
ByteArrayMethods.containsByte(Object base, long offset, long length, byte target):broadcasts the target byte to all 8 lanes of a word, then for each 8-byte word XORs and
applies the classic exact "a word contains a zero byte" test
(w - 0x0101010101010101L) & ~w & 0x8080808080808080L. It reports only existence, notposition, so it is endianness independent. Alignment handling mirrors
arrayEquals.UTF8String.containstakes anumBytes == 1fast path delegating to it, which also dropsthe redundant per-position
matchAtcall.Why are the changes needed?
Containssingle-character predicates are common ('%,%','%@%','% %','%/%'). Thecurrent byte-at-a-time scan reads through
Platform.getByte(Unsafe), which the JIT cannotauto-vectorize, so it processes one byte per iteration.
Does this PR introduce any user-facing change?
No.
How was this patch tested?
UTF8StringSuite.containsgains single-byte cases (first byte, past the first word, lastbyte, absent, sub-word length); the property-based
UTF8StringPropertyCheckSuitealso passes.Local microbenchmark (needle absent, i.e. full scan), nanoseconds per call:
Was this patch authored or co-authored using generative AI tooling?
Generated-by: Claude Opus 4.8