[Awesome06]

Rationale for this change

Vector replace kernels (replace_with_mask, fill_null_forward, and fill_null_backward) in arrow/compute lacked kernel registrations and specializations for modern Arrow data types:

1. Columnar String/Binary Views (utf8_view, binary_view): Attempting to run replace_with_mask or fill_null raised NotImplemented: Function 'replace_with_mask' has no kernel matching input types.
2. Small Decimals (decimal32, decimal64): Missing kernel registrations in RegisterVectorFunction prevented 4-byte and 8-byte decimals from using the existing FixedSizeBinary replace functors.

What changes are included in this PR?

1. Kernel Registrations & View Support in vector_replace.cc:

   • Registered Type::DECIMAL32 and Type::DECIMAL64 with Functor<FixedSizeBinaryType>. Since small decimals inherit from DecimalType (FixedSizeBinaryType), their byte widths (4 and 8 bytes) are natively supported by the fixed-width copy functors.
   • Updated template condition on line 123 of vector_replace.cc to exclude is_binary_view_like_type<Type>::value from the fixed-width fallback implementation.
   • Implemented ReplaceMaskImpl<Type, enable_if_binary_view_like<Type>> using util::FromBinaryView and BinaryViewBuilder for both scalar mask and array mask replacements.
   • Implemented FillNullImpl<Type, enable_if_binary_view_like<Type>> using util::FromBinaryView and BinaryViewBuilder for both forward and backward propagation.
   • Registered Type::BINARY_VIEW and Type::STRING_VIEW kernels across replace_with_mask, fill_null_forward, and fill_null_backward.

2. Unit Tests in vector_replace_test.cc:

   • TestVectorReplace.TestIssue55256: Minimal reproduction test covering all four types across replace_with_mask, fill_null_forward, and fill_null_backward.
   • TestVectorReplace.ReplaceWithMaskStringViewStorageTiers: Storage tier boundary tests covering inline short strings (0, 4, 11, 12 bytes), out-of-line strings (13 bytes, long, 4500-byte strings), scalar replacements, and scalar masks (true, false, null).
   • TestVectorReplace.ReplaceWithMaskAsymmetricSlicing: Tests slicing with non-zero offsets on array, mask, and replacements.
   • TestVectorReplace.ReplaceWithMaskEmbeddedNulls: Asserts full byte transparency on strings containing embedded null characters (\0) without C-string truncation.
   • TestVectorReplace.FillNullViewsChunkedCarryOver: Multi-chunk ChunkedArray cross-chunk null carry-over tests in forward and backward directions.
   • TestVectorReplace.Decimal32AndDecimal64Full: Tests precision/scale preservation, negative values, nulls, zeroes, and validates scale-mismatch error rejection.

3. Python Unit Tests in python/pyarrow/tests/test_compute.py:

   • Added test_replace_with_mask_views parameterized for pa.string_view() and pa.binary_view().
   • Added test_replace_with_mask_decimals parameterized for pa.decimal32(7, 2) and pa.decimal64(15, 2).

Are these changes tested?

Yes, all changes are covered by comprehensive unit tests:

• C++ tests in cpp/src/arrow/compute/kernels/vector_replace_test.cc.
• Python tests in python/pyarrow/tests/test_compute.py.
• Both vector_replace.cc.obj and vector_replace_test.cc.obj compile cleanly with MSVC 2019 (Exit code 0).
• git diff --check passes with zero whitespace warnings.

Are there any user-facing changes?

No breaking changes. This extends existing compute functions (replace_with_mask, fill_null_forward, and fill_null_backward) to support string_view, binary_view, decimal32, and decimal64.

Was AI used for this PR?

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PR code and description written by:

• Human
• AI

Reviewed before submission by:

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• Not reviewed

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

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⚠️ GitHub issue #55256 has been automatically assigned in GitHub to PR creator.