Pandas to_sql TypeError unsupported operand type

I am doing a database insertion using Pandas to_sql to move millions of rows into sqlalchemy. I've created a small test csv with only 4 rows so that I know exactly what data is in the file.

Here is the csv format

column_one,column_two,column_three,column_four
0001-1234,db38ad21b3,https://example.com,2
0034-1201,38db21adb3,https://example-two.com,3

My database table is defined with the exact same column names.

df = pd.read_csv("test_repositories.csv", 
        header=0, 
        sep=',',
        quotechar='"',
        dtype={'column_one': str,
            'column_two': str,
            'column_three': str,
            'column_four': int},
            error_bad_lines=False)
df = df.where(pd.notnull(df), None)
df.to_sql(self.staging_table, db.engine, self.chunksize, method='multi')

This seems like it should work, however I keep getting the following TypeError saying that the operation schema + "." + name can't support str + int

  File "/ingest/utils.py", line 59, in copy_csv_to_temp_table
    df.to_sql(self.staging_table, db.engine, self.chunksize, method='multi')
  File "/venv/lib/python3.8/site-packages/pandas/core/generic.py", line 2776, in to_sql
    sql.to_sql(
  File "/venv/lib/python3.8/site-packages/pandas/io/sql.py", line 590, in to_sql
    pandas_sql.to_sql(
  File "/venv/lib/python3.8/site-packages/pandas/io/sql.py", line 1382, in to_sql
    table = SQLTable(
  File "/venv/lib/python3.8/site-packages/pandas/io/sql.py", line 700, in __init__
    self.table = self._create_table_setup()
  File "/venv/lib/python3.8/site-packages/pandas/io/sql.py", line 966, in _create_table_setup
    return Table(self.name, meta, *columns, schema=schema)
  File "<string>", line 2, in __new__
  File "/venv/lib/python3.8/site-packages/sqlalchemy/util/deprecations.py", line 139, in warned
    return fn(*args, **kwargs)
  File "/venv/lib/python3.8/site-packages/sqlalchemy/sql/schema.py", line 537, in __new__
    key = _get_table_key(name, schema)
  File "/venv/lib/python3.8/site-packages/sqlalchemy/sql/schema.py", line 77, in _get_table_key
    return schema + "." + name
TypeError: unsupported operand type(s) for +: 'int' and 'str'

I understand what this error means. However, I don't understand why schema or name would cause a problem as all the column names are clearly strings. Any help is appreciated.

The function signature is:

DataFrame.to_sql(name, con, schema=None, if_exists='fail', index=True, index_label=None, chunksize=None, dtype=None, method=None)

Note that schema is the 3rd positional argument defaulted to None.

Therefore by using:

df.to_sql(self.staging_table, db.engine, self.chunksize, method='multi')

What you think is the chunksize is being interpreted as the schema argument, so change your chunksize to be explicitly named, eg:

df.to_sql(self.staging_table, db.engine, chunksize=self.chunksize, method='multi')