Add boolean type support to Parquet variant field extraction

[abigalekim]

Description

Adds boolean type support to Apache Parquet variant field extraction.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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📝 Walkthrough

Summary by CodeRabbit

• New Features
  • Added support for casting VARIANT boolean values to BOOL8, including correct decoding of true/false and proper handling of sliced multi-row inputs.
• Documentation
  • Updated VARIANT cast/extract documentation to list BOOL8 as a supported target/destination type and clarified desired_type/throwing behavior.
• Bug Fixes
  • Malformed or internally inconsistent VARIANT data now yields null results (instead of throwing), including during boolean handling.
• Tests
  • Expanded and refactored VARIANT cast/extract tests to generate payloads programmatically, added BOOL8 casting coverage, and added cases for malformed inputs and unsupported cast targets.

Walkthrough

VARIANT casting now supports Apache boolean primitives as BOOL8 output. CUDA decoding and null-mask handling were updated, documentation was expanded, and tests cover boolean values, nulls, slices, malformed inputs, cast matrices, and boundary cases.

Changes

VARIANT boolean casting

Layer / File(s)	Summary
VARIANT type contract alignment cpp/include/cudf/io/experimental/variant.hpp, cpp/src/io/parquet/experimental/variant_extract.cu	BOOL8 is documented and accepted as a VARIANT cast target.
Boolean decoding and output construction cpp/src/io/parquet/experimental/variant_extract.cu	Boolean VARIANT primitives are decoded, row spans use a shared helper, and valid values plus null masks are materialized as BOOL8 output.
Boolean cast validation cpp/tests/io/experimental/variant_extract_test.cpp	Encoding helpers and tests cover boolean, float, malformed, boundary, matrix, sliced, null, unsupported-target, and empty-input cases.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Possibly related PRs

• rapidsai/cudf#23036: Touches the VARIANT extraction implementation and test suite around basic and primitive type decoding.
• rapidsai/cudf#23069: Adds Java bindings that dispatch to the affected VARIANT extraction and casting APIs.
• rapidsai/cudf#23075: Modifies the VARIANT primitive casting implementation and predicate logic.

Suggested labels: tests, cuIO, improvement, 3 - Ready for Review

Suggested reviewers: vyasr, mhaseeb123, qbacpey

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: adding boolean support to Parquet VARIANT field extraction.
Description check	✅ Passed	The description is directly related to the changeset and accurately describes the boolean support update.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@cpp/tests/io/experimental/variant_extract_test.cpp`:
- Around line 661-675: Add BOOL8 test coverage in
CastVariantTest.ApachePrimitiveBooleans for a null boolean input and a sliced
multi-row input. Reuse the existing cast_variant path and column comparison
pattern, ensuring expected validity masks and values verify null handling and
grid-stride processing.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: 27916a08-ddf7-4798-b096-5e8d9d69216f

📥 Commits

Reviewing files that changed from the base of the PR and between af9ac19 and 64ea909.

📒 Files selected for processing (3)

• cpp/include/cudf/io/experimental/variant.hpp
• cpp/src/io/parquet/experimental/variant_extract.cu
• cpp/tests/io/experimental/variant_extract_test.cpp

[vuule]

There's a lot of conflicting changes between this PR and #23075. Let's merge that one before moving on with this one.

[abigalekim]

/ok to test 97845f5

[abigalekim]

/ok to test b730c80

[vuule]

few small suggestions

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

cpp/tests/io/experimental/variant_extract_test.cpp (1)

976-1045: 🎯 Functional Correctness | 🟠 Major | ⚡ Quick win

Add a multi-block BOOL8 cast case.

The sliced multi-row test does not exercise cast_variant_bool_kernel beyond one 256-thread block. Add at least block_size + 1 rows, including true, false, and null values, and validate the output mask after casting. As per coding guidelines, “Tests must cover empty inputs, nulls, sliced columns, boundary and multi-block sizes.”

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@cpp/tests/io/experimental/variant_extract_test.cpp` around lines 976 - 1045,
Extend the sliced multi-row case in ApachePrimitiveBooleans so the input
contains more than one cast_variant_bool_kernel block, using at least 257 rows
while retaining true, false, and null patterns. Keep the non-zero slice offset
and update expected values and validity to match the enlarged range, then assert
the cast output including its null mask.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@cpp/tests/io/experimental/variant_extract_test.cpp`:
- Around line 976-1045: Extend the sliced multi-row case in
ApachePrimitiveBooleans so the input contains more than one
cast_variant_bool_kernel block, using at least 257 rows while retaining true,
false, and null patterns. Keep the non-zero slice offset and update expected
values and validity to match the enlarged range, then assert the cast output
including its null mask.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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📥 Commits

Reviewing files that changed from the base of the PR and between b730c80 and 0bab85c.

📒 Files selected for processing (2)

• cpp/src/io/parquet/experimental/variant_extract.cu
• cpp/tests/io/experimental/variant_extract_test.cpp

[abigalekim]

/ok to test 69bd1d0

[abigalekim]

/ok to test 98040d5

[mhaseeb123]

Please take care of one more comment. LGTM otherwise

[abigalekim]

/ok to test 5dd9e23

[PointKernel]

/merge