Move / minimize number of cudf / dask-cudf imports (#480)

* Move / minimize number of cudf / dask-cudf imports

* Add tests for GPU-related errors

* Fix unbound local error

* Fix ddf value error

dask_sql/input_utils/dask.py

@@ -4,11 +4,6 @@
 
 from dask_sql.input_utils.base import BaseInputPlugin
 
-try:
-    import dask_cudf
-except ImportError:
-    dask_cudf = None
-
 
 class DaskInputPlugin(BaseInputPlugin):
     """Input Plugin for Dask DataFrames, just keeping them"""
@@ -27,7 +22,9 @@ def to_dc(
         **kwargs
     ):
         if gpu:  # pragma: no cover
-            if not dask_cudf:
+            try:
+                import dask_cudf
+            except ImportError:
                 raise ModuleNotFoundError(
                     "Setting `gpu=True` for table creation requires dask_cudf"
                 )

dask_sql/input_utils/location.py

@@ -7,11 +7,6 @@
 from dask_sql.input_utils.base import BaseInputPlugin
 from dask_sql.input_utils.convert import InputUtil
 
-try:
-    import dask_cudf
-except ImportError:
-    dask_cudf = None
-
 
 class LocationInputPlugin(BaseInputPlugin):
     """Input Plugin for everything, which can be read in from a file (on disk, remote etc.)"""
@@ -44,7 +39,9 @@ def to_dc(
             format = extension.lstrip(".")
         try:
             if gpu:  # pragma: no cover
-                if not dask_cudf:
+                try:
+                    import dask_cudf
+                except ImportError:
                     raise ModuleNotFoundError(
                         "Setting `gpu=True` for table creation requires dask-cudf"
                     )

dask_sql/input_utils/pandaslike.py

@@ -3,11 +3,6 @@
 
 from dask_sql.input_utils.base import BaseInputPlugin
 
-try:
-    import cudf
-except ImportError:
-    cudf = None
-
 
 class PandasLikeInputPlugin(BaseInputPlugin):
     """Input Plugin for Pandas Like DataFrames, which get converted to dask DataFrames"""
@@ -30,7 +25,9 @@ def to_dc(
     ):
         npartitions = kwargs.pop("npartitions", 1)
         if gpu:  # pragma: no cover
-            if not cudf:
+            try:
+                import cudf
+            except ImportError:
                 raise ModuleNotFoundError(
                     "Setting `gpu=True` for table creation requires cudf"
                 )

dask_sql/physical/rel/logical/aggregate.py

@@ -8,11 +8,6 @@
 import pandas as pd
 from dask import config as dask_config
 
-try:
-    import dask_cudf
-except ImportError:
-    dask_cudf = None
-
 from dask_sql.datacontainer import ColumnContainer, DataContainer
 from dask_sql.physical.rel.base import BaseRelPlugin
 from dask_sql.physical.rex.core.call import IsNullOperation
@@ -83,7 +78,7 @@ def get_supported_aggregation(self, series):
 
             if pd.api.types.is_string_dtype(series.dtype):
                 # If dask_cudf strings dtype, return built-in aggregation
-                if dask_cudf is not None and isinstance(series, dask_cudf.Series):
+                if "cudf" in str(series._partition_type):
                     return built_in_aggregation
 
                 # With pandas StringDtype built-in aggregations work

dask_sql/physical/utils/sort.py

@@ -6,11 +6,6 @@
 
 from dask_sql.utils import make_pickable_without_dask_sql
 
-try:
-    import dask_cudf
-except ImportError:
-    dask_cudf = None
-
 
 def apply_sort(
     df: dd.DataFrame,
@@ -35,10 +30,7 @@ def apply_sort(
 
     # dask / dask-cudf don't support lists of ascending / null positions
     if len(sort_columns) == 1 or (
-        dask_cudf is not None
-        and isinstance(df, dask_cudf.DataFrame)
-        and single_ascending
-        and single_null_first
+        "cudf" in str(df._partition_type) and single_ascending and single_null_first
     ):
         try:
             return df.sort_values(

tests/integration/test_create.py

@@ -363,3 +363,34 @@ def test_drop(c):
 
     with pytest.raises(dask_sql.utils.ParsingException):
         c.sql("SELECT a FROM new_table")
+
+
+def test_create_gpu_error(c, df, temporary_data_file):
+    try:
+        import cudf
+    except ImportError:
+        cudf = None
+
+    if cudf is not None:
+        pytest.skip("GPU-related import errors only need to be checked on CPU")
+
+    with pytest.raises(ModuleNotFoundError):
+        c.create_table("new_table", df, gpu=True)
+
+    with pytest.raises(ModuleNotFoundError):
+        c.create_table("new_table", dd.from_pandas(df, npartitions=2), gpu=True)
+
+    df.to_csv(temporary_data_file, index=False)
+
+    with pytest.raises(ModuleNotFoundError):
+        c.sql(
+            f"""
+            CREATE TABLE
+                new_table
+            WITH (
+                location = '{temporary_data_file}',
+                format = 'csv',
+                gpu = True
+            )
+        """
+        )