HashidaTKS commented on a change in pull request #10990: URL: https://github.com/apache/arrow/pull/10990#discussion_r714908656
########## File path: csharp/src/Apache.Arrow/Arrays/ArrayDataConcatenator.cs ########## @@ -0,0 +1,240 @@ +// Licensed to the Apache Software Foundation (ASF) under one or more +// contributor license agreements. See the NOTICE file distributed with +// this work for additional information regarding copyright ownership. +// The ASF licenses this file to You under the Apache License, Version 2.0 +// (the "License"); you may not use this file except in compliance with +// the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +using Apache.Arrow.Memory; +using Apache.Arrow.Types; +using System; +using System.Collections.Generic; + +namespace Apache.Arrow +{ + public static class ArrayDataConcatenator + { + public static ArrayData Concatenate(IReadOnlyList<ArrayData> arrayDataList, MemoryAllocator allocator = default) + { + if (arrayDataList == null || arrayDataList.Count == 0) + { + return null; + } + + if (arrayDataList.Count == 1) + { + return arrayDataList[0]; + } + + var arrowArrayConcatinateVisitor = new ArrayDataConcatinationVisitor(arrayDataList, allocator); + + IArrowType type = arrayDataList[0].DataType; + type.Accept(arrowArrayConcatinateVisitor); + + return arrowArrayConcatinateVisitor.Result; + } + + private class ArrayDataConcatinationVisitor : + IArrowTypeVisitor<BooleanType>, + IArrowTypeVisitor<FixedWidthType>, + IArrowTypeVisitor<BinaryType>, + IArrowTypeVisitor<StringType>, + IArrowTypeVisitor<ListType>, + IArrowTypeVisitor<StructType> + { + public ArrayData Result { get; private set; } + private IReadOnlyList<ArrayData> _arrayDataList; + private readonly int _totalLength; + private readonly int _totalNullCount; + private readonly MemoryAllocator _allocator; + + public ArrayDataConcatinationVisitor(IReadOnlyList<ArrayData> arrayDataList, MemoryAllocator allocator = default) + { + _arrayDataList = arrayDataList; + _allocator = allocator; + + foreach (ArrayData arrayData in _arrayDataList) + { + _totalLength += arrayData.Length; + _totalNullCount += arrayData.NullCount; + } + } + + public void Visit(BooleanType type) + { + CheckData(type, 2); + ArrowBuffer validityBuffer = ConcatenateValidityBuffer(); + ArrowBuffer valueBuffer = ConcatenateBitmapBuffer(1); + + Result = new ArrayData(type, _totalLength, _totalNullCount, 0, new ArrowBuffer[] { validityBuffer, valueBuffer }); + } + + public void Visit(FixedWidthType type) + { + CheckData(type, 2); + ArrowBuffer validityBuffer = ConcatenateValidityBuffer(); + ArrowBuffer valueBuffer = ConcatenateFixedWidthTypeValueBuffer(type); + + Result = new ArrayData(type, _totalLength, _totalNullCount, 0, new ArrowBuffer[] { validityBuffer, valueBuffer }); + } + + public void Visit(BinaryType type) => ConcateneteVariableBinaryArrayData(type); + + public void Visit(StringType type) => ConcateneteVariableBinaryArrayData(type); + + public void Visit(ListType type) + { + CheckData(type, 2); + ArrowBuffer validityBuffer = ConcatenateValidityBuffer(); + ArrowBuffer offsetBuffer = ConcateneteOffsetBuffer(); + ArrayData child = Concatenate(SelectChildren(0), _allocator); + + Result = new ArrayData(type, _totalLength, _totalNullCount, 0, new ArrowBuffer[] { validityBuffer, offsetBuffer }, new[] { child }); + } + + public void Visit(StructType type) + { + CheckData(type, 1); + List<ArrayData> children = new List<ArrayData>(type.Fields.Count); + + for (int i = 0; i < type.Fields.Count; i++) + { + children.Add(Concatenate(SelectChildren(i), _allocator)); + } + + Result = new ArrayData(type, _arrayDataList[0].Length, _arrayDataList[0].NullCount, 0, _arrayDataList[0].Buffers, children); + } + + public void Visit(IArrowType type) + { + throw new NotImplementedException($"Concatination for {type.Name} is not supported yet."); + } + + private void CheckData(IArrowType type, int expectedBufferCount) + { + foreach (ArrayData arrayData in _arrayDataList) + { + arrayData.EnsureDataType(type.TypeId); + arrayData.EnsureBufferCount(expectedBufferCount); + } + } + + private void ConcateneteVariableBinaryArrayData(IArrowType type) + { + CheckData(type, 3); + ArrowBuffer validityBuffer = ConcatenateValidityBuffer(); + ArrowBuffer offsetBuffer = ConcateneteOffsetBuffer(); + ArrowBuffer valueBuffer = ConcatenateVariableBinaryValueBuffer(); + + Result = new ArrayData(type, _totalLength, _totalNullCount, 0, new ArrowBuffer[] { validityBuffer, offsetBuffer, valueBuffer }); + } + + private ArrowBuffer ConcatenateValidityBuffer() + { + if (_totalNullCount == 0) + { + return ArrowBuffer.Empty; + } + + return ConcatenateBitmapBuffer(0); + } + + private ArrowBuffer ConcatenateBitmapBuffer(int bufferIndex) + { + var builder = new ArrowBuffer.BitmapBuilder(_totalLength); + + foreach (ArrayData arrayData in _arrayDataList) + { + int length = arrayData.Length; + ReadOnlySpan<byte> span = arrayData.Buffers[bufferIndex].Span; + + for (int i = 0; i < length; i++) + { + builder.Append(span.IsEmpty || BitUtility.GetBit(span, i)); + } + } + + return builder.Build(_allocator); + } + + private ArrowBuffer ConcatenateFixedWidthTypeValueBuffer(FixedWidthType type) + { + int typeByteWidth = type.BitWidth / 8; + var builder = new ArrowBuffer.Builder<byte>(_totalLength * typeByteWidth); + + foreach (ArrayData arrayData in _arrayDataList) + { + int length = arrayData.Length; + int byteLength = length * typeByteWidth; + + builder.Append(arrayData.Buffers[1].Span.Slice(0, byteLength)); + } + + return builder.Build(_allocator); + } + + private ArrowBuffer ConcatenateVariableBinaryValueBuffer() + { + var builder = new ArrowBuffer.Builder<byte>(); + + foreach (ArrayData arrayData in _arrayDataList) + { + int lastOffset = arrayData.Buffers[1].Span.CastTo<int>()[arrayData.Length]; + builder.Append(arrayData.Buffers[2].Span.Slice(0, lastOffset)); + } + + return builder.Build(_allocator); + } + + private ArrowBuffer ConcateneteOffsetBuffer() + { + var builder = new ArrowBuffer.Builder<int>(_totalLength + 1); + int baseOffset = 0; + + builder.Append(0); + + foreach (ArrayData arrayData in _arrayDataList) + { + if (arrayData.Length == 0) + { + continue; + } + + // The first offset is always 0. + // It should be skipped because it duplicate to the last offset of builder. + ReadOnlySpan<int> span = arrayData.Buffers[1].Span.CastTo<int>().Slice(1, arrayData.Length); Review comment: It is a bit confusing, but the length of `arrayData.Buffers[1]` is `arrayData.Length + 1`, so I think being `arrayData.Length` is correct. -- This is an automated message from the Apache Git Service. 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