feat(python)!: Constrain access to globals from df.sql in favour of…

… top-level `pl.sql` (pola-rs#16598)

py-polars/polars/dataframe/frame.py

@@ -4728,13 +4728,9 @@ def sql(self, query: str, *, table_name: str = "self") -> Self:
         issue_unstable_warning(
             "`sql` is considered **unstable** (although it is close to being considered stable)."
         )
-        with SQLContext(
-            register_globals=True,
-            eager=True,
-        ) as ctx:
-            frames = {table_name: self} if table_name else {}
-            frames["self"] = self
-            ctx.register_many(frames)
+        with SQLContext(register_globals=False, eager=True) as ctx:
+            name = table_name if table_name else "self"
+            ctx.register(name=name, frame=self)
             return ctx.execute(query)  # type: ignore[return-value]
 
     def top_k(

py-polars/polars/lazyframe/frame.py

@@ -1367,13 +1367,9 @@ def sql(self, query: str, *, table_name: str = "self") -> Self:
         issue_unstable_warning(
             "`sql` is considered **unstable** (although it is close to being considered stable)."
         )
-        with SQLContext(
-            register_globals=True,
-            eager=False,
-        ) as ctx:
-            frames = {table_name: self} if table_name else {}
-            frames["self"] = self
-            ctx.register_many(frames)
+        with SQLContext(register_globals=False, eager=False) as ctx:
+            name = table_name if table_name else "self"
+            ctx.register(name=name, frame=self)
             return ctx.execute(query)  # type: ignore[return-value]
 
     def top_k(

py-polars/tests/unit/sql/test_miscellaneous.py

@@ -86,6 +86,22 @@ def test_distinct() -> None:
         ctx.execute("SELECT * FROM df")
 
 
+def test_frame_sql_globals_error() -> None:
+    df1 = pl.DataFrame({"a": [1, 2, 3], "b": [4, 5, 6]})
+    df2 = pl.DataFrame({"a": [2, 3, 4], "b": [7, 6, 5]})  # noqa: F841
+
+    query = """
+        SELECT df1.a, df2.b
+        FROM df2 JOIN df1 ON df1.a = df2.a
+        ORDER BY b DESC
+    """
+    with pytest.raises(ComputeError, match=".*not found.*"):
+        df1.sql(query=query)
+
+    res = pl.sql(query=query, eager=True)
+    assert res.to_dict(as_series=False) == {"a": [2, 3], "b": [7, 6]}
+
+
 def test_in_no_ops_11946() -> None:
     lf = pl.LazyFrame(
         [