PERF: GroupBy.cumsum (#43309)

Author: jbrockmendel

pandas/core/internals/managers.py

@@ -526,7 +526,13 @@ def get_numeric_data(self: T, copy: bool = False) -> T:
         copy : bool, default False
             Whether to copy the blocks
         """
-        return self._combine([b for b in self.blocks if b.is_numeric], copy)
+        numeric_blocks = [blk for blk in self.blocks if blk.is_numeric]
+        if len(numeric_blocks) == len(self.blocks):
+            # Avoid somewhat expensive _combine
+            if copy:
+                return self.copy(deep=True)
+            return self
+        return self._combine(numeric_blocks, copy)
 
     def _combine(
         self: T, blocks: list[Block], copy: bool = True, index: Index | None = None