[REVIEW] Optimizations for cudf.concat when axis=1

python/cudf/cudf/_lib/column.pyi

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from typing import Optional, Tuple, TypeVar, Union
+from typing import Dict, Optional, Tuple, TypeVar
 
 from cudf._typing import Dtype, DtypeObj, ScalarLike
 from cudf.core.buffer import Buffer
@@ -21,6 +21,7 @@ class Column:
     _null_count: int
     _children: Tuple[ColumnBase, ...]
     _base_children: Tuple[ColumnBase, ...]
+    _distinct_count: Dict[bool, int]
 
     def __init__(
         self,

python/cudf/cudf/_lib/column.pyx

@@ -80,6 +80,7 @@ cdef class Column:
 
         self._size = size
         self._cached_sizeof = None
+        self._distinct_count = None
         self._dtype = dtype
         self._offset = offset
         self._null_count = null_count
@@ -203,9 +204,14 @@ cdef class Column:
                 raise ValueError(error_msg)
 
         self._mask = None
-        self._null_count = None
         self._children = None
         self._base_mask = value
+        self._clear_cache()
+
+    def _clear_cache(self):
+        self._distinct_count = None
+        self._cached_sizeof = None
+        self._null_count = None
 
     def set_mask(self, value):
         """