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unwrapping slice makes it easier to see what is happening in these algorithms and makes it easier to optimize. Additionally this makes these functions usable without having to wrap them into a slice.
Benchmark (benchmarkCompareUtf16BE, length=1000): - ascii=true: 3.483 -> 0.102 ns/codepoint - ascii=false: 8.214 -> 6.395 ns/codepoint
Benchmark (benchmarkReverse, length=1000): - ascii=true: 0.318 -> 0.067 ns/codepoint - ascii=false: 3.397 -> 3.406 ns/codepoint (flat within noise)
Benchmark (benchmarkToUpperCase, length=1000): - ascii=true: 3.053 -> 0.601 ns/codepoint - ascii=false: 7.254 -> 5.019 ns/codepoint
Benchmark (benchmarkToLowerCase, length=1000): - ascii=true: 3.029 -> 0.501 ns/codepoint - ascii=false: 7.145 -> 4.183 ns/codepoint
Benchmark (benchmarkFixInvalidUtf8WithoutReplacement, inputLength=1024): - valid_non_ascii: 6.341 -> 3.978 ns/byte - invalid_non_ascii: 6.242 -> 4.549 ns/byte
Benchmark (benchmarkLeftTrim, length=1000): - ascii=true: 1.919 -> 0.344 ns/codepoint - ascii=false: 3.137 -> 2.201 ns/codepoint
Benchmark (benchmarkRightTrim, length=1000): - ascii=true: 0.551 -> 0.359 ns/codepoint - ascii=false: 2.939 -> 2.534 ns/codepoint
Benchmark (benchmarkTrimCustom, length=1000): - ascii=true: 2.702 -> 0.474 ns/codepoint - ascii=false: 5.224 -> 4.329 ns/codepoint
Benchmark (benchmarkSetCodePointAt, length=1000): - ascii=true: 0.336 -> 0.332 ns/codepoint - ascii=false: 2.259 -> 2.334 ns/codepoint Related benchmark (benchmarkCodePointToUtf8, length=1000): - ascii=false: 2.404 -> 2.154 ns/codepoint
Useful for Trino VARCHAR->code points casts and similar decode loops. Benchmark (ns/byte, length=1000): - toCodePointsApi ascii: 0.2319 (baseline two-pass: 2.4902) - toCodePointsApi non-ascii: 1.0820 (baseline two-pass: 1.6643)
Adds fromCodePoints to encode code-point arrays directly into UTF-8 Slice output. This is useful for Trino-style loops that currently pre-size and encode with repeated setCodePointAt calls. Benchmark (SliceUtf8Benchmark, length=1000 code points): - ascii=true: fromCodePointsApi 0.326 ns/codepoint vs Trino baseline 0.500 ns/codepoint - ascii=false: fromCodePointsApi 2.062 ns/codepoint vs Trino baseline 3.230 ns/codepoint
Adds codePointByteLengths so callers can decode UTF-8 once and directly materialize per-code-point byte widths (1..4) for padding/loop planning. Benchmark (SliceUtf8Benchmark, length=128 code points): - ascii=true: helper(byte[]) 0.696 ns/codepoint vs Trino byte[] baseline 1.020 ns/codepoint - ascii=false: helper(byte[]) 2.129 ns/codepoint vs Trino byte[] baseline 3.596 ns/codepoint
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No regressions in Trino. Slight CPU improvement for TPCH/TPCDS (~1%) |
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Summary
byte[] + offset + length, withSliceoverloads delegating.High-level optimization approaches
byte[]first internals: better JVM bounds-check hoisting and easier raw-array integration.long/intlanes via var handles) to skip equal ASCII regions quickly.New APIs
toCodePoints(byte[] utf8, int offset, int length)fromCodePoints(int[] codePoints, int offset, int length)codePointByteLengths(byte[] utf8, int offset, int length)Benchmark highlights (JMH)
Most results below are for
length=1000code points unless noted.benchmarkCompareUtf16BE3.483 -> 0.102 ns/codepoint(~34x)8.214 -> 6.395 ns/codepoint(~1.28x)benchmarkToLowerCase3.029 -> 0.501 ns/codepoint(~6.0x)7.145 -> 4.183 ns/codepoint(~1.71x)benchmarkToUpperCase3.053 -> 0.601 ns/codepoint(~5.1x)7.254 -> 5.019 ns/codepoint(~1.45x)benchmarkTrimCustom2.702 -> 0.474 ns/codepoint(~5.7x)5.224 -> 4.329 ns/codepoint(~1.21x)benchmarkLeftTrim1.919 -> 0.344 ns/codepoint(~5.6x)3.137 -> 2.201 ns/codepoint(~1.42x)benchmarkRightTrim0.551 -> 0.359 ns/codepoint(~1.53x)2.939 -> 2.534 ns/codepoint(~1.16x)benchmarkToCodePointsApi(ns/byte)2.4902 -> 0.2319(~10.7x vs two-pass baseline)1.6643 -> 1.0820(~1.54x vs two-pass baseline)benchmarkFromCodePointsApi0.500 -> 0.326 ns/codepoint(~1.53x)3.230 -> 2.062 ns/codepoint(~1.57x)benchmarkFixInvalidUtf8WithoutReplacement(inputLength=1024, ns/byte)6.341 -> 3.978(~1.59x)6.242 -> 4.549(~1.37x)benchmarkReverse0.318 -> 0.067 ns/codepoint(~4.7x)3.397 -> 3.406 ns/codepoint(flat/noise)codePointByteLengthshelper benchmark (length=128)1.020 -> 0.696 ns/codepoint(~1.47x)3.596 -> 2.129 ns/codepoint(~1.69x)Small-string sanity (tail paths)
Ran a dedicated JMH sanity pass at non-8-multiple lengths
7and31(withascii=true,false) for:compareUtf16BE,toLowerCase,toUpperCase,trimCustom,toCodePointsApi, andfromCodePointsApi.compareUtf16BE:7.332 / 10.781 ns/op(len=7 / 31)41.308 / 193.126 ns/opfromCodePointsApi:7.702 / 14.937 ns/op25.337 / 64.678 ns/optoCodePointsApi:5.843 / 12.206 ns/op29.565 / 123.929 ns/optoLowerCase:12.790 / 29.095 ns/op27.257 / 124.587 ns/optoUpperCase:7.894 / 23.449 ns/op36.579 / 124.978 ns/optrimCustom:18.294 / 29.761 ns/op54.013 / 170.847 ns/opConclusion: no obvious small-string regressions; short-input behavior is consistent with expected fixed-overhead effects.