perf: improve StringArray builder append paths#331
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CurtHagenlocher merged 4 commits intoapache:mainfrom Apr 26, 2026
Merged
perf: improve StringArray builder append paths#331CurtHagenlocher merged 4 commits intoapache:mainfrom
CurtHagenlocher merged 4 commits intoapache:mainfrom
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BenchmarkDotNet ShortRun, StringBuilderAppendBenchmark, 10,000 ASCII strings of length 32: - AppendSmallStrings: 432.0 us / 1.66 MB -> 341.0 us / 1157.5 KB - AppendRangeSmallStrings: 426.2 us / 1.66 MB -> 311.8 us / 353.68 KB
Write encoded string bytes directly into the builder value buffer after reserving capacity, avoiding both stackalloc staging and an extra copy while keeping offsets and validity updates unchanged. BenchmarkDotNet (StringBuilderAppendBenchmark): AppendSmallStrings 393.1 us / 1157.5 KB; AppendRangeSmallStrings 290.5 us / 353.68 KB.
Encapsulate the reserve/get-span/advance sequence in BinaryArray.BuilderBase so StringArray.Builder can encode directly into the value buffer without owning the low-level buffer length bookkeeping. BenchmarkDotNet (StringBuilderAppendBenchmark): AppendSmallStrings 383.7 us / 1157.5 KB; AppendRangeSmallStrings 294.4 us / 353.68 KB.
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Summary
StringArray.Builder.Append(string)values by encoding into stack memory before appending.AppendRangeinputs.AppendRange(ICollection<string>)now performs a counting prepass to reserve value-buffer capacity before appending, so collection inputs are enumerated twice by design.Benchmark
BenchmarkDotNet ShortRun,
StringBuilderAppendBenchmark, 10,000 ASCII strings of length 32:AppendSmallStringsAppendRangeSmallStringsValidation
dotnet test test/Apache.Arrow.Tests/Apache.Arrow.Tests.csproj -c Release --filter "FullyQualifiedName~Apache.Arrow.Tests.StringArrayTests"rtk dotnet build "Apache.Arrow.sln" -c Release