Fix old valid_count usage

python/cudf/cudf/core/column/categorical.py

@@ -1381,7 +1381,9 @@ def _concat(
         # improved as the concatenation API is solidified.
 
         # Find the first non-null column:
-        head = next((obj for obj in objs if not obj.has_nulls()), objs[0])
+        head = next(
+            (obj for obj in objs if not obj.null_count != len(obj)), objs[0]
+        )
 
         # Combine and de-dupe the categories
         cats = column.concat_columns([o.categories for o in objs]).unique()

python/cudf/cudf/core/column/column.py

@@ -2734,7 +2734,7 @@ def concat_columns(objs: "MutableSequence[ColumnBase]") -> ColumnBase:
     # If all columns are `NumericalColumn` with different dtypes,
     # we cast them to a common dtype.
     # Notice, we can always cast pure null columns
-    not_null_col_dtypes = [o.dtype for o in objs if not o.has_nulls()]
+    not_null_col_dtypes = [o.dtype for o in objs if o.null_count != len(o)]
     if len(not_null_col_dtypes) and all(
         _is_non_decimal_numeric_dtype(dtyp)
         and np.issubdtype(dtyp, np.datetime64)
@@ -2746,7 +2746,7 @@ def concat_columns(objs: "MutableSequence[ColumnBase]") -> ColumnBase:
         objs = [obj.astype(common_dtype) for obj in objs]
 
     # Find the first non-null column:
-    head = next((obj for obj in objs if not obj.has_nulls()), objs[0])
+    head = next((obj for obj in objs if obj.null_count != len(obj)), objs[0])
 
     for i, obj in enumerate(objs):
         # Check that all columns are the same type:

python/cudf/cudf/core/dataframe.py

@@ -8098,7 +8098,7 @@ def _get_non_null_cols_and_dtypes(col_idxs, list_of_columns):
             # non-null Column with the same name is found.
             if idx not in dtypes:
                 dtypes[idx] = cols[idx].dtype
-            if cols[idx].has_nulls():
+            if cols[idx].null_count != len(cols[idx]):
                 if idx not in non_null_columns:
                     non_null_columns[idx] = [cols[idx]]
                 else:

python/cudf/cudf/utils/dtypes.py

@@ -401,7 +401,7 @@ def min_column_type(x, expected_type):
 
     if not isinstance(x, cudf.core.column.NumericalColumn):
         raise TypeError("Argument x must be of type column.NumericalColumn")
-    if not x.has_nulls():
+    if x.null_count == len(x):
         return x.dtype
 
     if np.issubdtype(x.dtype, np.floating):