Reverting the last 3 commits to allow discussion

Author: chalmerlowe

packages/bigframes/bigframes/core/compile/sqlglot/sqlglot_ir.py

@@ -214,14 +214,8 @@ def from_table(
         if not columns and not sql_predicate:
             return cls.from_expr(expr=table_expr, uid_gen=uid_gen)
 
-        # Qualify column references with the table alias to avoid ambiguity
-        # when a table and a column share the same name. Without this, BigQuery
-        # might interpret the column as a reference to the table (STRUCT),
-        # causing failures when casting (e.g. in test_read_gbq_w_ambigous_name).
-        select_items: list[sge.Expression] = (
-            [sge.Column(this=sql.identifier(col), table=sql.identifier(table_alias)) for col in columns]
-            if columns
-            else [sge.Star()]
+        select_items: list[sge.Identifier | sge.Star] = (
+            [sql.identifier(col) for col in columns] if columns else [sge.Star()]
         )
         select_expr = sge.Select().select(*select_items).from_(table_expr)
 

packages/bigframes/bigframes/series.py

@@ -1146,12 +1146,10 @@ def nsmallest(self, n: int = 5, keep: str = "first") -> Series:
         )
 
     def isin(self, values) -> "Series":
-        # Block.isin can return nulls for non-matching rows, but pandas.isin
-        # always returns boolean (False for non-matches). We fill nulls with False.
         if isinstance(values, Series):
-            return Series(self._block.isin(values._block)).fillna(value=False)
+            return Series(self._block.isin(values._block))
         if isinstance(values, indexes.Index):
-            return Series(self._block.isin(values.to_series()._block)).fillna(value=False)
+            return Series(self._block.isin(values.to_series()._block))
         if not _is_list_like(values):
             raise TypeError(
                 "only list-like objects are allowed to be passed to "