为什么在 oracledbcx_Oracle (Python) 中不调用外转换器进行字节转换

我正在try 使用Python(3.11)和oracledb库(1.3.0)从Oracle数据库中获取SDO_GEOMETRY类型的列.我想使用outputtypeHandler将SDO_GEOMETRY实例转换为PICKLE编码的字节.如果我try 将cursor.var中的typ参数设置为typ=str，这对于数字列很有效，但对于所有类型的列类型，这对于typ=bytes和typ=oracledb.DB_TYPE_RAW都失败了.无论参数值为typ，SDO_GEOMETRY列始终会产生错误.输出转换器甚至不会被调用，如下所示.

以下是我的示例代码:

import oracledb
import pickle


def output_type_handler(cursor, name, default_type, size, precision, scale):

    def pickle_converter(obj) -> bytes:
        print(f"Converter called for {name}.")
        return pickle.dumps(obj)

    if default_type == oracledb.DB_TYPE_OBJECT:
        return cursor.var(
            typ=oracledb.DB_TYPE_RAW, 
            size=size, 
            arraysize=cursor.arraysize, 
            outconverter=pickle_converter
        )

# Switch to thick mode
oracledb.init_oracle_client()

ora_connection = oracledb.connect(
    dsn=oracledb.makedsn("ora.local", 1521, "TST"),
    user="test",
    password="test"
)

ora_connection.outputtypehandler = output_type_handler

with ora_connection.cursor() as cursor:
    # GEOMETRIE is an SDO_GEOMETRY column
    recs = cursor.execute("SELECT GEOMETRIE FROM MV_CS_STWG1KP").fetchmany(5)
    print(recs)

OUTPUT(请注意，行Converter called for ...甚至没有打印，因此从未调用转换器):

Traceback (most recent call last):
  File "/home/jannis/.config/JetBrains/PyCharmCE2023.1/scratches/tmp.py", line 28, in <module>
    num_recs = cursor.execute("SELECT GEOMETRIE FROM MV_CS_STWG1KP").fetchmany(5)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jannis/PycharmProjects/etl_engine/venv/lib/python3.11/site-packages/oracledb/cursor.py", line 492, in fetchmany
    row = fetch_next_row(self)
          ^^^^^^^^^^^^^^^^^^^^
  File "src/oracledb/impl/base/cursor.pyx", line 397, in oracledb.base_impl.BaseCursorImpl.fetch_next_row
  File "src/oracledb/impl/thick/cursor.pyx", line 132, in oracledb.thick_impl.ThickCursorImpl._fetch_rows
  File "src/oracledb/impl/thick/utils.pyx", line 413, in oracledb.thick_impl._raise_from_odpi
  File "src/oracledb/impl/thick/utils.pyx", line 403, in oracledb.thick_impl._raise_from_info
oracledb.exceptions.DatabaseError: ORA-00932: inconsistent datatypes: expected BINARY got ADT

我必须使用胖模式才能连接到较旧的Oracle数据库. 我怎么才能解决这个问题？