fix typing and sql default backend case

Author: jorisvandenbossche

pandas/io/_util.py

@@ -58,6 +58,7 @@ def arrow_table_to_pandas(
 ) -> pd.DataFrame:
     pa = import_optional_dependency("pyarrow")
 
+    types_mapper: type[pd.ArrowDtype] | None | Callable
     if dtype_backend == "numpy_nullable":
         mapping = _arrow_dtype_mapping()
         if null_to_int64:

pandas/io/sql.py

@@ -2210,6 +2210,9 @@ def read_table(
         with self.con.cursor() as cur:
             cur.execute(stmt)
             pa_table = cur.fetch_arrow_table()
+            dtype_backend = (
+                lib.no_default if dtype_backend == "numpy" else dtype_backend
+            )
             df = arrow_table_to_pandas(pa_table, dtype_backend=dtype_backend)
 
         return _wrap_result_adbc(
@@ -2281,6 +2284,9 @@ def read_query(
         with self.con.cursor() as cur:
             cur.execute(sql)
             pa_table = cur.fetch_arrow_table()
+            dtype_backend = (
+                lib.no_default if dtype_backend == "numpy" else dtype_backend
+            )
             df = arrow_table_to_pandas(pa_table, dtype_backend=dtype_backend)
 
         return _wrap_result_adbc(

pandas/tests/io/test_sql.py

@@ -959,12 +959,12 @@ def sqlite_buildin_types(sqlite_buildin, types_data):
 
 adbc_connectable_iris = [
     pytest.param("postgresql_adbc_iris", marks=pytest.mark.db),
-    pytest.param("sqlite_adbc_iris", marks=pytest.mark.db),
+    "sqlite_adbc_iris",
 ]
 
 adbc_connectable_types = [
     pytest.param("postgresql_adbc_types", marks=pytest.mark.db),
-    pytest.param("sqlite_adbc_types", marks=pytest.mark.db),
+    "sqlite_adbc_types",
 ]