[C++][Compute] Vector replace kernels (replace_with_mask, fill_null) do not support string_view, binary_view, decimal32, or decimal64 #55256

Describe the bug, including details regarding any error messages, version, and platform.

The vector replacement compute functions (replace_with_mask, fill_null_forward, and fill_null_backward) fail with arrow::Status::NotImplemented when invoked with:

• utf8_view (string_view) or binary_view
• Modern 32-bit and 64-bit decimal types (decimal32, decimal64)

While classic variable-length binary types (utf8, large_utf8, binary, large_binary), primitives, and Decimal128 / Decimal256 are supported, modern view types and small decimals are omitted from the kernel registration table.

In cpp/src/arrow/compute/kernels/vector_replace.cc, RegisterVectorFunction registers fixed-size binary, legacy decimals, and BaseBinaryTypes():

AddKernel(Type::FIXED_SIZE_BINARY,
          Functor<FixedSizeBinaryType>::GetSignature(Type::FIXED_SIZE_BINARY),
          Functor<FixedSizeBinaryType>::Exec, ChunkedFunctor<FixedSizeBinaryType>::Exec,
          registry, func.get());
AddKernel(Type::DECIMAL128,
          Functor<FixedSizeBinaryType>::GetSignature(Type::DECIMAL128),
          Functor<FixedSizeBinaryType>::Exec, ChunkedFunctor<FixedSizeBinaryType>::Exec,
          registry, func.get());
AddKernel(Type::DECIMAL256,
          Functor<FixedSizeBinaryType>::GetSignature(Type::DECIMAL256),
          Functor<FixedSizeBinaryType>::Exec, ChunkedFunctor<FixedSizeBinaryType>::Exec,
          registry, func.get());
for (const auto& ty : BaseBinaryTypes()) {
  AddKernel(ty->id(), Functor<FixedSizeBinaryType>::GetSignature(ty->id()),
            GenerateTypeAgnosticVarBinaryBase<Functor>(*ty),
            GenerateTypeAgnosticVarBinaryBase<ChunkedFunctor>(*ty), registry,
            func.get());
}

Because replace_with_mask, fill_null_forward, and fill_null_backward all instantiate kernels via this template helper, none of them support:

1. BinaryViewType or StringViewType (BaseBinaryTypes() only covers binary, large_binary, utf8, large_utf8).
2. Decimal32Type or Decimal64Type (only DECIMAL128 and DECIMAL256 are registered).

Reproduction

The issue reproduces in C++ (and PyArrow):

TEST(TestVectorReplace, StringViewAndSmallDecimals) {
  // 1. replace_with_mask on utf8_view
  auto view_arr = ArrayFromJSON(utf8_view(), "[\"apple\", null, \"cherry\"]");
  auto mask = ArrayFromJSON(boolean(), "[false, true, false]");
  auto replacements = ArrayFromJSON(utf8_view(), "[\"banana\"]");

  auto res1 = arrow::compute::ReplaceWithMask(view_arr, mask, replacements);
  ASSERT_OK(res1.status());

  // 2. fill_null_forward on utf8_view
  auto res2 = arrow::compute::FillNullForward(view_arr);
  ASSERT_OK(res2.status());

  // 3. replace_with_mask on decimal32
  auto dec32_type = decimal32(7, 2);
  auto dec_arr = ArrayFromJSON(dec32_type, "[\"12.34\", null, \"56.78\"]");
  auto dec_repl = ArrayFromJSON(dec32_type, "[\"99.99\"]");

  auto res3 = arrow::compute::ReplaceWithMask(dec_arr, mask, dec_repl);
  ASSERT_OK(res3.status());
}

Or in Python:

import pyarrow as pa
import pyarrow.compute as pc

# 1. string_view replace_with_mask
views = pa.array(["apple", None, "cherry"], type=pa.string_view())
mask = pa.array([False, True, False])
repl = pa.array(["banana"], type=pa.string_view())

pc.replace_with_mask(views, mask, repl)

# 2. string_view fill_null_forward
pc.fill_null_forward(views)

# 3. decimal32 replace_with_mask
dec_arr = pa.array([1234, None, 5678], type=pa.decimal32(7, 2))
dec_repl = pa.array([9999], type=pa.decimal32(7, 2))
pc.replace_with_mask(dec_arr, mask, dec_repl)

Expected:

• replace_with_mask(views, mask, repl) returns string_view array ["apple", "banana", "cherry"].
• fill_null_forward(views) returns string_view array ["apple", "apple", "cherry"].
• replace_with_mask(dec_arr, mask, dec_repl) returns decimal32(7, 2) array ["12.34", "99.99", "56.78"].

Actual:

ArrowNotImplementedError: Function 'replace_with_mask' has no kernel matching input types (string_view, boolean, string_view)
ArrowNotImplementedError: Function 'fill_null_forward' has no kernel matching input types (string_view)
ArrowNotImplementedError: Function 'fill_null_backward' has no kernel matching input types (string_view)
ArrowNotImplementedError: Function 'replace_with_mask' has no kernel matching input types (decimal32(7, 2), boolean, decimal32(7, 2))

Reproduced on current main across all platforms. This is an unfiled type-matrix parity gap in Arrow C++ compute.

Suggested fix

1. For decimal32 and decimal64:
   In RegisterVectorFunction in cpp/src/arrow/compute/kernels/vector_replace.cc, register Type::DECIMAL32 and Type::DECIMAL64 matching the existing DECIMAL128 fixed-width pattern:

   AddKernel(Type::DECIMAL32,
             Functor<FixedSizeBinaryType>::GetSignature(Type::DECIMAL32),
             Functor<FixedSizeBinaryType>::Exec, ChunkedFunctor<FixedSizeBinaryType>::Exec,
             registry, func.get());
   AddKernel(Type::DECIMAL64,
             Functor<FixedSizeBinaryType>::GetSignature(Type::DECIMAL64),
             Functor<FixedSizeBinaryType>::Exec, ChunkedFunctor<FixedSizeBinaryType>::Exec,
             registry, func.get());

2. For string_view and binary_view:
   Add view-aware execution functors to vector_replace.cc and copy_data_internal.h:

   • Copy the 16-byte view descriptors (StringViewType::c_type) during element replacement or propagation.
   • For replace_with_mask, merge the data buffers of the replacement array/scalar into the output array's data->buffers.
   • For fill_null_forward / fill_null_backward, forward the 16-byte descriptors directly and retain the input array's data buffers.

3. Add Unit Tests:
   Add test coverage in cpp/src/arrow/compute/kernels/vector_replace_test.cc verifying:

   • Sliced view arrays with non-zero offsets.
   • Runs of multiple consecutive nulls with fill_null_forward and fill_null_backward.
   • Array-array and array-scalar replacement permutations for utf8_view, binary_view, decimal32, and decimal64.

Component(s)

C++