[BUG] [GPU Error Bug] "SELECT (('b햦]D7Jr31')||((CASE 'Kx}lzJ^' WHEN <column> THEN '' END ))) FROM <table>" brings Error

[qwebug]

What happened:

"SELECT (('b햦]D7Jr31')||((CASE 'Kx}lzJ^' WHEN <column> THEN '' END ))) FROM <table> " brings error, when using GPU.

However it is able to output result, when using CPU.

What you expected to happen:

It will not bring error, when using GPU.

Minimal Complete Verifiable Example:

import pandas as pd
import dask.dataframe as dd
from dask_sql import Context

c = Context()

df0 = pd.DataFrame({
    'c0': ['e'],
    'c1': ['o'],
})
t0 = dd.from_pandas(df0, npartitions=1)
c.create_table('t0', t0, gpu=False)
c.create_table('t0_gpu', t0, gpu=True)

print('CPU Result:')
result1= c.sql("SELECT (('b햦]D7Jr31')||((CASE 'Kx}lzJ^' WHEN t0.c1 THEN '' END ))) FROM t0").compute()
print(result1)

print('GPU Result:')
result2= c.sql("SELECT (('b햦]D7Jr31')||((CASE 'Kx}lzJ^' WHEN t0_gpu.c1 THEN '' END ))) FROM t0_gpu").compute()
print(result2)

Result:

INFO:numba.cuda.cudadrv.driver:init
CPU Result:
  Utf8("b햦]D7Jr31") || CASE Utf8("Kx}lzJ^") WHEN t0.c1 THEN Utf8("") END
0                                                NaN                    
GPU Result:
Traceback (most recent call last):
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/cudf/core/indexed_frame.py", line 2180, in _apply
    kernel, retty = _compile_or_get(
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/nvtx/nvtx.py", line 101, in inner
    result = func(*args, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/cudf/core/udf/utils.py", line 268, in _compile_or_get
    kernel, scalar_return_type = kernel_getter(frame, func, args)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/cudf/core/udf/scalar_function.py", line 55, in _get_scalar_kernel
    scalar_return_type = _get_udf_return_type(sr_type, func, args)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/nvtx/nvtx.py", line 101, in inner
    result = func(*args, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/cudf/core/udf/utils.py", line 88, in _get_udf_return_type
    ptx, output_type = cudautils.compile_udf(func, compile_sig)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/cudf/utils/cudautils.py", line 258, in compile_udf
    output_type = numpy_support.as_dtype(return_type).type
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/numba/np/numpy_support.py", line 159, in as_dtype
    raise errors.NumbaNotImplementedError(msg)
numba.core.errors.NumbaNotImplementedError: unicode_type cannot be represented as a NumPy dtype

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/tmp/bug17/bug17.py", line 20, in <module>
    result2= c.sql("SELECT (('b햦]D7Jr31')||((CASE 'Kx}lzJ^' WHEN t0_gpu.c1 THEN '' END ))) FROM t0_gpu").compute()
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/base.py", line 314, in compute
    (result,) = compute(self, traverse=False, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/base.py", line 599, in compute
    results = schedule(dsk, keys, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/threaded.py", line 89, in get
    results = get_async(
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/local.py", line 511, in get_async
    raise_exception(exc, tb)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/local.py", line 319, in reraise
    raise exc
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/local.py", line 224, in execute_task
    result = _execute_task(task, data)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/core.py", line 119, in _execute_task
    return func(*(_execute_task(a, cache) for a in args))
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/optimization.py", line 990, in __call__
    return core.get(self.dsk, self.outkey, dict(zip(self.inkeys, args)))
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/core.py", line 149, in get
    result = _execute_task(task, cache)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/core.py", line 119, in _execute_task
    return func(*(_execute_task(a, cache) for a in args))
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/core.py", line 119, in <genexpr>
    return func(*(_execute_task(a, cache) for a in args))
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/core.py", line 119, in _execute_task
    return func(*(_execute_task(a, cache) for a in args))
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/core.py", line 119, in <genexpr>
    return func(*(_execute_task(a, cache) for a in args))
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/core.py", line 119, in _execute_task
    return func(*(_execute_task(a, cache) for a in args))
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/utils.py", line 73, in apply
    return func(*args, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/dataframe/core.py", line 7006, in apply_and_enforce
    df = func(*args, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/dask/utils.py", line 1105, in __call__
    return getattr(__obj, self.method)(*args, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/nvtx/nvtx.py", line 101, in inner
    result = func(*args, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/cudf/core/series.py", line 2473, in apply
    result = self._apply(func, _get_scalar_kernel, *args, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/contextlib.py", line 79, in inner
    return func(*args, **kwds)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/nvtx/nvtx.py", line 101, in inner
    result = func(*args, **kwargs)
  File "/opt/conda/envs/rapids/lib/python3.10/site-packages/cudf/core/indexed_frame.py", line 2184, in _apply
    raise ValueError(
ValueError: user defined function compilation failed.

Anything else we need to know?:

Environment:

• dask-sql version: 2023.6.0
• Python version: Python 3.10.11
• Operating System: Ubuntu22.04
• Install method (conda, pip, source): Docker deploy by https://hub.docker.com/layers/rapidsai/rapidsai-dev/23.06-cuda11.8-devel-ubuntu22.04-py3.10/images/sha256-cfbb61fdf7227b090a435a2e758114f3f1c31872ed8dbd96e5e564bb5fd184a7?context=explore