[VL] Unify gpu hash shuffle writer output

[marin-ma]

Currently, gpu shuffle writer splits the boolean and timestamp vector to buffers that is same as arrow/cudf format because it assumes the shuffle reader stage will execute on GPU and use gpu shuffle reader. However, the stage execution is decided at runtime when AQE is on. If the next stage is planed to execute on CPU, the shuffle read will fail.

In order to support a more general hybrid execution mode, it's necessary to unify the cpu/gpu shuffle writer output for a specific shuffle writer type (currently hash or sort).

[Copilot]

Pull request overview

This PR aligns GPU-hash shuffle writer output with the CPU/hash shuffle writer so that shuffle data remains readable when AQE changes the downstream stage to CPU execution (hybrid CPU/GPU mode).

Changes:

• Route kGpuHashShuffle writer creation through VeloxHashShuffleWriter to unify on a single hash-shuffle output format.
• Remove the dedicated VeloxGpuHashShuffleWriter implementation and shift boolean/timestamp value normalization into GpuBufferColumnarBatch::compose.
• Update JNI/test option wiring to use HashShuffleWriterOptions.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
cpp/velox/tests/VeloxGpuShuffleWriterTest.cc	Updates GPU-hash test configuration to use HashShuffleWriterOptions.
cpp/velox/shuffle/VeloxShuffleWriter.cc	Treats kGpuHashShuffle as an alias for hash shuffle writer creation.
cpp/velox/shuffle/VeloxGpuShuffleWriter.h	Removes the GPU hash shuffle writer class definition.
cpp/velox/shuffle/VeloxGpuShuffleWriter.cc	Removes the GPU hash shuffle writer implementation.
cpp/velox/memory/GpuBufferColumnarBatch.cc	Adds boolean/timestamp value conversions when composing GPU buffer batches.
cpp/velox/CMakeLists.txt	Drops the removed GPU shuffle writer source from the GPU build.
cpp/core/jni/JniWrapper.cc	Switches GPU-hash JNI writer creation to HashShuffleWriterOptions.

Comments suppressed due to low confidence (1)

cpp/core/jni/JniWrapper.cc:1105

• createGpuHashShuffleWriter now builds a HashShuffleWriterOptions, which defaults shuffleWriterType to kHashShuffle. Since VeloxRuntime::createShuffleWriter selects the writer using options->shuffleWriterType, this JNI API will no longer create a kGpuHashShuffle writer (behavior change vs the previous GpuHashShuffleWriterOptions). If the caller still expects a GPU-hash writer type, set shuffleWriterType explicitly after construction.

  auto shuffleWriterOptions = std::make_shared<HashShuffleWriterOptions>(
      toPartitioning(jStringToCString(env, partitioningNameJstr)),
      startPartitionId,
      splitBufferSize,
      splitBufferReallocThreshold);

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.