gpu-scan-cli scan --gpu-file panics with "as_slice must be called on host buffer"

[manish-sethi]

What happened?

Summary

gpu-scan-cli scan --gpu-file panics on every Vortex file I produce via gpu-scan-cli convert.

Immediate panic on every tokio worker:

2026-05-07T01:11:35Z INFO vortex_cuda: Registering CUDA kernels

thread 'tokio-rt-worker' panicked at vortex-error/src/lib.rs:361:13:
Assertion failed error: as_slice must be called on host buffer
0: PrimitiveData::as_slice
1: Primitive::scalar_at
2: ArrayRef::execute_scalar
3: Patches::chunk_offset_at
4: Patches::search_index
5: Patches::slice
6: BitPacked::slice
7: BitPacked::reduce_parent
8: ArrayRef::slice
9: FoR::slice
10: FoR::reduce_parent
11: ArrayRef::slice
12: CudaFlatReader::projection_evaluation
13: ChunkedReader::projection_evaluation
14: StructReader::projection_evaluation
15: scan::tasks::split_exec

(Many threads panic in parallel; backtrace is the same on each.)

Steps to reproduce

# 1. Build the tools                                      
cargo build --release -p vortex-tui -p gpu-scan-cli
                                                                                                                                                                                
# 2. Ingest a Parquet file (TPC-H SF100 `lineitem`)
./target/release/vx convert lineitem.parquet                                                                                                                                    
# → lineitem.vortex                                                                                                                                                   
                                                                                                                                                                                
# 3. Re-encode for CUDA                                                                                                                                                         
./target/release/gpu-scan-cli convert \                                                                                                                                         
  --input  lineitem.vortex \                                                                                                                                                    
  --output lineitem.cuda.vortex                                                                                                                                                 
# → succeeds                                                                                                                                                                    
                                                                                                                                                                                
# 4. Scan                                                 
RUST_LOG=info RUST_BACKTRACE=1 \
  ./target/release/gpu-scan-cli scan lineitem.cuda.vortex --gpu-file                                                                                                            
# → panics                                                    

### Environment

- Vortex commit a9dc3a2eb (develop)
- CUDA 13.0
- Linux aarch64 (NVIDIA GB10)                                                                                                                                                   
- Tested on TPC-H SF100 lineitem; reproduces consistently

### Additional context

I tried excluding ALPScheme and ALPRDScheme from only_cuda_compatible(), thinking the patches were ALP-related, but the same panic still occurs — looks like integer columns also trigger it.

[joseph-isaacs]

Sorry about this we are in the process of migrating these. Ill have a fix up soon

[joseph-isaacs]

fixed here: #7839