remove aggregate_size block method

Author: TrevorBergeron

bigframes/core/blocks.py

@@ -1347,37 +1347,6 @@ def aggregate_all_and_stack(
             block, id = self.project_expr(reduced, None)
             return block.select_column(id)
 
-    def aggregate_size(
-        self,
-        by_column_ids: typing.Sequence[str] = (),
-        *,
-        dropna: bool = True,
-    ):
-        """Returns a block object to compute the size(s) of groups."""
-        agg_specs = [
-            (
-                agg_expressions.NullaryAggregation(agg_ops.SizeOp()),
-                guid.generate_guid(),
-            ),
-        ]
-        output_col_ids = [agg_spec[1] for agg_spec in agg_specs]
-        result_expr = self.expr.aggregate(agg_specs, by_column_ids, dropna=dropna)
-        names: typing.List[Label] = []
-        for by_col_id in by_column_ids:
-            if by_col_id in self.value_columns:
-                names.append(self.col_id_to_label[by_col_id])
-            else:
-                names.append(self.col_id_to_index_name[by_col_id])
-        return (
-            Block(
-                result_expr,
-                index_columns=by_column_ids,
-                column_labels=["size"],
-                index_labels=names,
-            ),
-            output_col_ids,
-        )
-
     def select_column(self, id: str) -> Block:
         return self.select_columns([id])
 

bigframes/core/groupby/dataframe_group_by.py

@@ -182,7 +182,8 @@ def __len__(self) -> int:
         return len(self.agg([]))
 
     def size(self) -> typing.Union[df.DataFrame, series.Series]:
-        agg_block, _ = self._block.aggregate_size(
+        agg_block = self._block.aggregate(
+            aggregations=[agg_ops.SizeOp().as_expr()],
             by_column_ids=self._by_col_ids,
             dropna=self._dropna,
         )

bigframes/core/groupby/series_group_by.py

@@ -189,7 +189,8 @@ def var(self, *args, **kwargs) -> series.Series:
         return self._aggregate(agg_ops.var_op)
 
     def size(self) -> series.Series:
-        agg_block, _ = self._block.aggregate_size(
+        agg_block = self._block.aggregate(
+            aggregations=[agg_ops.SizeOp().as_expr()],
             by_column_ids=self._by_col_ids,
             dropna=self._dropna,
         )