Backport PR #47474 on branch 1.4.x (BUG: to_sql with method=callable not returning int raising TypeError) (#47590)

Backport PR #47474: BUG: to_sql with method=callable not returning int raising TypeError

Co-authored-by: Matthew Roeschke <emailformattr@gmail.com>

Author: meeseeksmachine

doc/source/whatsnew/v1.4.4.rst

@@ -24,7 +24,7 @@ Fixed regressions
 Bug fixes
 ~~~~~~~~~
 - The :class:`errors.FutureWarning` raised when passing arguments (other than ``filepath_or_buffer``) as positional in :func:`read_csv` is now raised at the correct stacklevel (:issue:`47385`)
--
+- Bug in :meth:`DataFrame.to_sql` when ``method`` was a ``callable`` that did not return an ``int`` and would raise a ``TypeError`` (:issue:`46891`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/generic.py

@@ -2847,7 +2847,7 @@ def to_sql(
         -------
         None or int
             Number of rows affected by to_sql. None is returned if the callable
-            passed into ``method`` does not return the number of rows.
+            passed into ``method`` does not return an integer number of rows.
 
             The number of returned rows affected is the sum of the ``rowcount``
             attribute of ``sqlite3.Cursor`` or SQLAlchemy connectable which may not

pandas/io/sql.py

@@ -33,6 +33,7 @@
 from pandas.core.dtypes.common import (
     is_datetime64tz_dtype,
     is_dict_like,
+    is_integer,
     is_list_like,
 )
 from pandas.core.dtypes.dtypes import DatetimeTZDtype
@@ -670,7 +671,7 @@ def to_sql(
     -------
     None or int
         Number of rows affected by to_sql. None is returned if the callable
-        passed into ``method`` does not return the number of rows.
+        passed into ``method`` does not return an integer number of rows.
 
         .. versionadded:: 1.4.0
 
@@ -938,7 +939,7 @@ def insert(
             raise ValueError("chunksize argument should be non-zero")
 
         chunks = (nrows // chunksize) + 1
-        total_inserted = 0
+        total_inserted = None
         with self.pd_sql.run_transaction() as conn:
             for i in range(chunks):
                 start_i = i * chunksize
@@ -948,10 +949,12 @@ def insert(
 
                 chunk_iter = zip(*(arr[start_i:end_i] for arr in data_list))
                 num_inserted = exec_insert(conn, keys, chunk_iter)
-                if num_inserted is None:
-                    total_inserted = None
-                else:
-                    total_inserted += num_inserted
+                # GH 46891
+                if is_integer(num_inserted):
+                    if total_inserted is None:
+                        total_inserted = num_inserted
+                    else:
+                        total_inserted += num_inserted
         return total_inserted
 
     def _query_iterator(

pandas/tests/io/test_sql.py

@@ -621,7 +621,8 @@ def test_read_procedure(conn, request):
 
 @pytest.mark.db
 @pytest.mark.parametrize("conn", postgresql_connectable)
-def test_copy_from_callable_insertion_method(conn, request):
+@pytest.mark.parametrize("expected_count", [2, "Success!"])
+def test_copy_from_callable_insertion_method(conn, expected_count, request):
     # GH 8953
     # Example in io.rst found under _io.sql.method
     # not available in sqlite, mysql
@@ -642,10 +643,18 @@ def psql_insert_copy(table, conn, keys, data_iter):
 
             sql_query = f"COPY {table_name} ({columns}) FROM STDIN WITH CSV"
             cur.copy_expert(sql=sql_query, file=s_buf)
+        return expected_count
 
     conn = request.getfixturevalue(conn)
     expected = DataFrame({"col1": [1, 2], "col2": [0.1, 0.2], "col3": ["a", "n"]})
-    expected.to_sql("test_frame", conn, index=False, method=psql_insert_copy)
+    result_count = expected.to_sql(
+        "test_frame", conn, index=False, method=psql_insert_copy
+    )
+    # GH 46891
+    if not isinstance(expected_count, int):
+        assert result_count is None
+    else:
+        assert result_count == expected_count
     result = sql.read_sql_table("test_frame", conn)
     tm.assert_frame_equal(result, expected)