[GitHub] [arrow] bkietz commented on a change in pull request #10412: ARROW-9430: [C++] Implement replace_with_mask kernel

[GitBox <gi...@apache.org>]

bkietz commented on a change in pull request #10412:
URL: https://github.com/apache/arrow/pull/10412#discussion_r669046761



##########
File path: cpp/src/arrow/compute/kernels/vector_replace.cc
##########
@@ -0,0 +1,510 @@
+// 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.
+
+#include "arrow/compute/api_scalar.h"
+#include "arrow/compute/kernels/common.h"
+#include "arrow/util/bitmap_ops.h"
+
+namespace arrow {
+namespace compute {
+namespace internal {
+
+namespace {
+
+Status ReplacementArrayTooShort(int64_t expected, int64_t actual) {
+  return Status::Invalid("Replacement array must be of appropriate length (expected ",
+                         expected, " items but got ", actual, " items)");
+}
+
+// Helper to implement replace_with kernel with scalar mask for fixed-width types,
+// using callbacks to handle both bool and byte-sized types
+Status ReplaceWithScalarMask(KernelContext* ctx, const ArrayData& array,
+                             const BooleanScalar& mask, const Datum& replacements,
+                             ArrayData* output) {
+  if (!mask.is_valid) {
+    // Output = null
+    ARROW_ASSIGN_OR_RAISE(auto replacement_array,
+                          MakeArrayOfNull(array.type, array.length, ctx->memory_pool()));
+    *output = *replacement_array->data();
+    return Status::OK();
+  }
+  if (mask.value) {
+    // Output = replacement
+    if (replacements.is_scalar()) {
+      ARROW_ASSIGN_OR_RAISE(
+          auto replacement_array,
+          MakeArrayFromScalar(*replacements.scalar(), array.length, ctx->memory_pool()));
+      *output = *replacement_array->data();
+    } else {
+      auto replacement_array = replacements.array();
+      if (replacement_array->length != array.length) {
+        return ReplacementArrayTooShort(array.length, replacement_array->length);
+      }
+      *output = *replacement_array;
+    }
+  } else {
+    // Output = input
+    *output = array;
+  }
+  return Status::OK();
+}
+
+struct CopyArrayBitmap {
+  const uint8_t* in_bitmap;
+  int64_t in_offset;
+
+  void CopyBitmap(uint8_t* out_bitmap, int64_t out_offset, int64_t offset,
+                  int64_t length) const {
+    arrow::internal::CopyBitmap(in_bitmap, in_offset + offset, length, out_bitmap,
+                                out_offset);
+  }
+
+  void SetBit(uint8_t* out_bitmap, int64_t out_offset, int64_t offset) const {
+    BitUtil::SetBitTo(out_bitmap, out_offset,
+                      BitUtil::GetBit(in_bitmap, in_offset + offset));
+  }
+};
+
+struct CopyScalarBitmap {
+  const bool is_valid;
+
+  void CopyBitmap(uint8_t* out_bitmap, int64_t out_offset, int64_t offset,
+                  int64_t length) const {
+    BitUtil::SetBitsTo(out_bitmap, out_offset, length, is_valid);
+  }
+
+  void SetBit(uint8_t* out_bitmap, int64_t out_offset, int64_t offset) const {
+    BitUtil::SetBitTo(out_bitmap, out_offset, is_valid);
+  }
+};
+
+// Helper to implement replace_with kernel with array mask for fixed-width types,
+// using callbacks to handle both bool and byte-sized types and to handle
+// scalar and array replacements
+template <typename Functor, typename Data, typename CopyBitmap>
+void ReplaceWithArrayMaskImpl(const ArrayData& array, const ArrayData& mask,
+                              const Data& replacements, bool replacements_bitmap,
+                              const CopyBitmap copy_bitmap, const uint8_t* mask_bitmap,
+                              const uint8_t* mask_values, uint8_t* out_bitmap,
+                              uint8_t* out_values, const int64_t out_offset) {
+  Functor::CopyData(*array.type, out_values, /*out_offset=*/0, array, /*in_offset=*/0,
+                    array.length);
+  arrow::internal::OptionalBinaryBitBlockCounter counter(
+      mask_values, mask.offset, mask_bitmap, mask.offset, mask.length);
+  int64_t write_offset = 0;
+  int64_t replacements_offset = 0;
+  while (write_offset < array.length) {
+    BitBlockCount block = counter.NextAndBlock();
+    if (block.AllSet()) {
+      // Copy from replacement array
+      Functor::CopyData(*array.type, out_values, out_offset + write_offset, replacements,
+                        replacements_offset, block.length);
+      if (replacements_bitmap) {
+        copy_bitmap.CopyBitmap(out_bitmap, out_offset + write_offset, replacements_offset,
+                               block.length);
+      } else if (!replacements_bitmap && out_bitmap) {
+        BitUtil::SetBitsTo(out_bitmap, out_offset + write_offset, block.length, true);
+      }
+      replacements_offset += block.length;
+    } else if (block.popcount) {
+      for (int64_t i = 0; i < block.length; ++i) {
+        if (BitUtil::GetBit(mask_values, write_offset + mask.offset + i) &&
+            (!mask_bitmap ||
+             BitUtil::GetBit(mask_bitmap, write_offset + mask.offset + i))) {
+          Functor::CopyData(*array.type, out_values, out_offset + write_offset + i,
+                            replacements, replacements_offset, /*length=*/1);
+          if (replacements_bitmap) {
+            copy_bitmap.SetBit(out_bitmap, out_offset + write_offset + i,
+                               replacements_offset);
+          }
+          replacements_offset++;
+        }
+      }
+    }
+    write_offset += block.length;
+  }
+}
+
+template <typename Functor>
+Status ReplaceWithArrayMask(KernelContext* ctx, const ArrayData& array,
+                            const ArrayData& mask, const Datum& replacements,
+                            ArrayData* output) {
+  const int64_t out_offset = output->offset;
+  uint8_t* out_bitmap = nullptr;
+  uint8_t* out_values = output->buffers[1]->mutable_data();
+  const uint8_t* mask_bitmap = mask.MayHaveNulls() ? mask.buffers[0]->data() : nullptr;
+  const uint8_t* mask_values = mask.buffers[1]->data();
+  const bool replacements_bitmap = replacements.is_array()
+                                       ? replacements.array()->MayHaveNulls()
+                                       : !replacements.scalar()->is_valid;
+  if (replacements.is_array()) {
+    // Check that we have enough replacement values
+    const int64_t replacements_length = replacements.array()->length;
+
+    arrow::internal::OptionalBinaryBitBlockCounter counter(
+        mask_values, mask.offset, mask_bitmap, mask.offset, mask.length);
+    int64_t count = 0;
+    for (int64_t offset = 0; offset < mask.length;) {
+      BitBlockCount block = counter.NextAndBlock();
+      count += block.popcount;
+      offset += block.length;
+    }
+    if (count > replacements_length) {
+      return ReplacementArrayTooShort(count, replacements_length);
+    }
+  }
+  if (array.MayHaveNulls() || mask.MayHaveNulls() || replacements_bitmap) {
+    out_bitmap = output->buffers[0]->mutable_data();
+    output->null_count = -1;
+    if (array.MayHaveNulls()) {
+      // Copy array's bitmap
+      arrow::internal::CopyBitmap(array.buffers[0]->data(), array.offset, array.length,
+                                  out_bitmap, out_offset);
+    } else {
+      // Array has no bitmap but mask/replacements do, generate an all-valid bitmap
+      BitUtil::SetBitsTo(out_bitmap, out_offset, array.length, true);
+    }
+  } else {
+    BitUtil::SetBitsTo(output->buffers[0]->mutable_data(), out_offset, array.length,
+                       true);
+    output->null_count = 0;
+  }
+
+  if (replacements.is_array()) {
+    const ArrayData& array_repl = *replacements.array();
+    ReplaceWithArrayMaskImpl<Functor>(
+        array, mask, array_repl, replacements_bitmap,
+        CopyArrayBitmap{replacements_bitmap ? array_repl.buffers[0]->data() : nullptr,
+                        array_repl.offset},
+        mask_bitmap, mask_values, out_bitmap, out_values, out_offset);
+  } else {
+    const Scalar& scalar_repl = *replacements.scalar();
+    ReplaceWithArrayMaskImpl<Functor>(array, mask, scalar_repl, replacements_bitmap,
+                                      CopyScalarBitmap{scalar_repl.is_valid}, mask_bitmap,
+                                      mask_values, out_bitmap, out_values, out_offset);
+  }
+
+  if (mask.MayHaveNulls()) {
+    arrow::internal::BitmapAnd(out_bitmap, out_offset, mask.buffers[0]->data(),
+                               mask.offset, array.length, out_offset, out_bitmap);
+  }
+  return Status::OK();
+}
+
+template <typename Type, typename Enable = void>
+struct ReplaceWithMask {};
+
+template <typename Type>
+struct ReplaceWithMask<Type, enable_if_number<Type>> {
+  using T = typename TypeTraits<Type>::CType;
+
+  static void CopyData(const DataType&, uint8_t* out, const int64_t out_offset,
+                       const ArrayData& in, const int64_t in_offset,
+                       const int64_t length) {
+    const auto in_arr = in.GetValues<uint8_t>(1, (in_offset + in.offset) * sizeof(T));
+    std::memcpy(out + (out_offset * sizeof(T)), in_arr, length * sizeof(T));
+  }
+
+  static void CopyData(const DataType&, uint8_t* out, const int64_t out_offset,
+                       const Scalar& in, const int64_t in_offset, const int64_t length) {
+    T* begin = reinterpret_cast<T*>(out + (out_offset * sizeof(T)));
+    T* end = begin + length;
+    std::fill(begin, end, UnboxScalar<Type>::Unbox(in));
+  }
+
+  static Status ExecScalarMask(KernelContext* ctx, const ArrayData& array,
+                               const BooleanScalar& mask, const Datum& replacements,
+                               ArrayData* output) {
+    return ReplaceWithScalarMask(ctx, array, mask, replacements, output);
+  }
+
+  static Status ExecArrayMask(KernelContext* ctx, const ArrayData& array,
+                              const ArrayData& mask, const Datum& replacements,
+                              ArrayData* output) {
+    return ReplaceWithArrayMask<ReplaceWithMask<Type>>(ctx, array, mask, replacements,
+                                                       output);
+  }
+};
+
+template <typename Type>
+struct ReplaceWithMask<Type, enable_if_boolean<Type>> {
+  static void CopyData(const DataType&, uint8_t* out, const int64_t out_offset,
+                       const ArrayData& in, const int64_t in_offset,
+                       const int64_t length) {
+    const auto in_arr = in.GetValues<uint8_t>(1, /*absolute_offset=*/0);
+    arrow::internal::CopyBitmap(in_arr, in_offset + in.offset, length, out, out_offset);
+  }
+  static void CopyData(const DataType&, uint8_t* out, const int64_t out_offset,
+                       const Scalar& in, const int64_t in_offset, const int64_t length) {
+    BitUtil::SetBitsTo(out, out_offset, length, in.is_valid);
+  }
+
+  static Status ExecScalarMask(KernelContext* ctx, const ArrayData& array,
+                               const BooleanScalar& mask, const Datum& replacements,
+                               ArrayData* output) {
+    return ReplaceWithScalarMask(ctx, array, mask, replacements, output);
+  }
+  static Status ExecArrayMask(KernelContext* ctx, const ArrayData& array,
+                              const ArrayData& mask, const Datum& replacements,
+                              ArrayData* output) {
+    return ReplaceWithArrayMask<ReplaceWithMask<Type>>(ctx, array, mask, replacements,
+                                                       output);
+  }
+};
+
+template <typename Type>
+struct ReplaceWithMask<Type, enable_if_same<Type, FixedSizeBinaryType>> {
+  static void CopyData(const DataType& ty, uint8_t* out, const int64_t out_offset,
+                       const ArrayData& in, const int64_t in_offset,
+                       const int64_t length) {
+    const int32_t width = checked_cast<const FixedSizeBinaryType&>(ty).byte_width();
+    uint8_t* begin = out + (out_offset * width);
+    const auto in_arr = in.GetValues<uint8_t>(1, (in_offset + in.offset) * width);
+    std::memcpy(begin, in_arr, length * width);
+  }
+  static void CopyData(const DataType& ty, uint8_t* out, const int64_t out_offset,
+                       const Scalar& in, const int64_t in_offset, const int64_t length) {
+    const int32_t width = checked_cast<const FixedSizeBinaryType&>(ty).byte_width();
+    uint8_t* begin = out + (out_offset * width);
+    const auto& scalar = checked_cast<const FixedSizeBinaryScalar&>(in);
+    // Null scalar may have null value buffer
+    if (!scalar.value) return;
+    const Buffer& buffer = *scalar.value;
+    const uint8_t* value = buffer.data();
+    DCHECK_GE(buffer.size(), width);
+    for (int i = 0; i < length; i++) {
+      std::memcpy(begin, value, width);
+      begin += width;
+    }
+  }
+
+  static Status ExecScalarMask(KernelContext* ctx, const ArrayData& array,
+                               const BooleanScalar& mask, const Datum& replacements,
+                               ArrayData* output) {
+    return ReplaceWithScalarMask(ctx, array, mask, replacements, output);
+  }
+
+  static Status ExecArrayMask(KernelContext* ctx, const ArrayData& array,
+                              const ArrayData& mask, const Datum& replacements,
+                              ArrayData* output) {
+    return ReplaceWithArrayMask<ReplaceWithMask<Type>>(ctx, array, mask, replacements,
+                                                       output);
+  }
+};
+
+template <typename Type>
+struct ReplaceWithMask<Type, enable_if_decimal<Type>> {
+  using ScalarType = typename TypeTraits<Type>::ScalarType;
+  static void CopyData(const DataType& ty, uint8_t* out, const int64_t out_offset,
+                       const ArrayData& in, const int64_t in_offset,
+                       const int64_t length) {
+    const int32_t width = checked_cast<const FixedSizeBinaryType&>(ty).byte_width();
+    uint8_t* begin = out + (out_offset * width);
+    const auto in_arr = in.GetValues<uint8_t>(1, (in_offset + in.offset) * width);
+    std::memcpy(begin, in_arr, length * width);
+  }
+  static void CopyData(const DataType& ty, uint8_t* out, const int64_t out_offset,
+                       const Scalar& in, const int64_t in_offset, const int64_t length) {
+    const int32_t width = checked_cast<const FixedSizeBinaryType&>(ty).byte_width();
+    uint8_t* begin = out + (out_offset * width);
+    const auto& scalar = checked_cast<const ScalarType&>(in);
+    const auto value = scalar.value.ToBytes();
+    for (int i = 0; i < length; i++) {
+      std::memcpy(begin, value.data(), width);
+      begin += width;
+    }
+  }
+
+  static Status ExecScalarMask(KernelContext* ctx, const ArrayData& array,
+                               const BooleanScalar& mask, const Datum& replacements,
+                               ArrayData* output) {
+    return ReplaceWithScalarMask(ctx, array, mask, replacements, output);
+  }
+
+  static Status ExecArrayMask(KernelContext* ctx, const ArrayData& array,
+                              const ArrayData& mask, const Datum& replacements,
+                              ArrayData* output) {
+    return ReplaceWithArrayMask<ReplaceWithMask<Type>>(ctx, array, mask, replacements,
+                                                       output);
+  }
+};
+
+template <typename Type>
+struct ReplaceWithMask<Type, enable_if_null<Type>> {
+  static Status ExecScalarMask(KernelContext* ctx, const ArrayData& array,
+                               const BooleanScalar& mask, const Datum& replacements,
+                               ArrayData* output) {
+    *output = array;
+    return Status::OK();
+  }
+  static Status ExecArrayMask(KernelContext* ctx, const ArrayData& array,
+                              const ArrayData& mask, const Datum& replacements,
+                              ArrayData* output) {
+    *output = array;
+    return Status::OK();
+  }
+};
+
+template <typename Type>
+struct ReplaceWithMask<Type, enable_if_base_binary<Type>> {
+  using offset_type = typename Type::offset_type;
+  using BuilderType = typename TypeTraits<Type>::BuilderType;
+
+  static Status ExecScalarMask(KernelContext* ctx, const ArrayData& array,
+                               const BooleanScalar& mask, const Datum& replacements,
+                               ArrayData* output) {
+    return ReplaceWithScalarMask(ctx, array, mask, replacements, output);
+  }
+  static Status ExecArrayMask(KernelContext* ctx, const ArrayData& array,
+                              const ArrayData& mask, const Datum& replacements,
+                              ArrayData* output) {
+    BuilderType builder(array.type, ctx->memory_pool());
+    RETURN_NOT_OK(builder.Reserve(array.length));
+    RETURN_NOT_OK(builder.ReserveData(array.buffers[2]->size()));
+    int64_t source_offset = 0;
+    int64_t replacements_offset = 0;
+    RETURN_NOT_OK(VisitArrayDataInline<BooleanType>(
+        mask,
+        [&](bool replace) {
+          if (replace && replacements.is_scalar()) {
+            const Scalar& scalar = *replacements.scalar();
+            if (scalar.is_valid) {
+              RETURN_NOT_OK(builder.Append(UnboxScalar<Type>::Unbox(scalar)));
+            } else {
+              RETURN_NOT_OK(builder.AppendNull());
+            }
+          } else {
+            const ArrayData& source = replace ? *replacements.array() : array;
+            const int64_t offset = replace ? replacements_offset++ : source_offset;
+            if (!source.MayHaveNulls() ||
+                BitUtil::GetBit(source.buffers[0]->data(), source.offset + offset)) {
+              const uint8_t* data = source.buffers[2]->data();
+              const offset_type* offsets = source.GetValues<offset_type>(1);
+              const offset_type offset0 = offsets[offset];
+              const offset_type offset1 = offsets[offset + 1];
+              RETURN_NOT_OK(builder.Append(data + offset0, offset1 - offset0));
+            } else {
+              RETURN_NOT_OK(builder.AppendNull());
+            }
+          }
+          source_offset++;
+          return Status::OK();
+        },
+        [&]() {
+          RETURN_NOT_OK(builder.AppendNull());
+          source_offset++;
+          return Status::OK();
+        }));
+    std::shared_ptr<Array> temp_output;
+    RETURN_NOT_OK(builder.Finish(&temp_output));
+    *output = *temp_output->data();
+    // Builder type != logical type due to GenerateTypeAgnosticVarBinaryBase
+    output->type = array.type;
+    return Status::OK();
+  }
+};
+
+template <typename Type>
+struct ReplaceWithMaskFunctor {
+  static Status Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
+    const ArrayData& array = *batch[0].array();
+    const Datum& replacements = batch[2];
+    ArrayData* output = out->array().get();
+    output->length = array.length;
+
+    // Needed for FixedSizeBinary/parameterized types
+    if (!array.type->Equals(*replacements.type(), /*check_metadata=*/false)) {
+      return Status::Invalid("Replacements must be of same type (expected ",
+                             array.type->ToString(), " but got ",
+                             replacements.type()->ToString(), ")");
+    }
+
+    if (!replacements.is_array() && !replacements.is_scalar()) {
+      return Status::Invalid("Replacements must be array or scalar");
+    }
+
+    if (batch[1].is_scalar()) {
+      return ReplaceWithMask<Type>::ExecScalarMask(
+          ctx, array, batch[1].scalar_as<BooleanScalar>(), replacements, output);
+    }
+    const ArrayData& mask = *batch[1].array();
+    if (array.length != mask.length) {
+      return Status::Invalid("Mask must be of same length as array (expected ",
+                             array.length, " items but got ", mask.length, " items)");
+    }
+    return ReplaceWithMask<Type>::ExecArrayMask(ctx, array, mask, replacements, output);
+  }
+};
+
+}  // namespace
+
+const FunctionDoc replace_with_mask_doc(
+    "Replace items using a mask and replacement values",
+    ("Given an array and a Boolean mask (either scalar or of equal length), "
+     "along with replacement values (either scalar or array), "
+     "each element of the array for which the corresponding mask element is "
+     "true will be replaced by the next value from the replacements, "
+     "or with null if the mask is null. "
+     "Hence, for replacement arrays, len(replacements) == sum(mask == true)."),
+    {"values", "mask", "replacements"});
+
+void RegisterVectorReplace(FunctionRegistry* registry) {
+  auto func = std::make_shared<VectorFunction>("replace_with_mask", Arity::Ternary(),
+                                               &replace_with_mask_doc);
+  auto add_kernel = [&](detail::GetTypeId get_id, ArrayKernelExec exec) {
+    VectorKernel kernel;
+    kernel.can_execute_chunkwise = false;
+    if (is_fixed_width(get_id.id)) {
+      kernel.null_handling = NullHandling::type::COMPUTED_PREALLOCATE;
+    } else {
+      kernel.can_write_into_slices = false;
+      kernel.null_handling = NullHandling::type::COMPUTED_NO_PREALLOCATE;
+    }
+    kernel.mem_allocation = MemAllocation::type::PREALLOCATE;

Review comment:
       It is unfortunate that we don't have a versatile utility for vector functions like CheckScalar. One way to verify correct writing into slices would be: run the function once to ensure output is correctly allocated/shaped/etc, then invoke the kernel directly into a slice of that output. If everything is working as it should, the kernel should simply overwrite that slice with new values, leaving values outside the slice untouched.




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