'str' object has no attribute 'read' on Oracle LONG columns

While performing queries on UnicodeText columns, or reflected LONG columns, I get the following error (tested on 0.7.8, I faced it after upgrade to 0.7.8, IIRC from 0.6.1 but I am not sure):

Traceback (most recent call last):
  File "sqlalchemy_long_bug.py", line 35, in <module>
    print item
  File "/home/marcink/.virtualenvs/ias/lib/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-i686.egg/sqlalchemy/engine/base.py", line 2680, in __repr__
    return repr(tuple(self))
  File "/home/marcink/.virtualenvs/ias/lib/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-i686.egg/sqlalchemy/dialects/oracle/cx_oracle.py", line 218, in process
    return value.read()
AttributeError: 'str' object has no attribute 'read'

My platform: Ubuntu 10.04, python 2.6.5, SQLAlchemy 0.7.8, cx_Oracle-5.1.2, Oracle 10g, NLS_LANG=polish_poland.EE8ISO8859P2 (but NSL_LANG does not seem to matter).

Debugging shows, that _LOBMixin tries to call value.read() when value already is in fact string with exact column value. My bet is that there is some disagreement between cx_Oracle and SQLALchemy cx_oracle driver about output types.

Forcing column type to {{{UnicodeText}}} (instead of reflection) does not help, the same error.

Forcing column type to {{{String}}} helps.

Example script:

# -*- coding: utf-8 -*-

"""
Before running this script, execute the following SQL:

    CREATE TABLE slb_test(id INTEGER, value LONG);

    INSERT INTO slb_test VALUES (1, 'aaaaa');
    INSERT INTO slb_test VALUES (2, 'bbbbbb');
    COMMIT;

and fix DB_URI beelow.

"""

DB_URI="oracle://scott:tiger@my.db.machine:5521/DB"

import sqlalchemy
import sqlalchemy.orm

engine = sqlalchemy.create_engine(DB_URI)
metadata = sqlalchemy.MetaData(bind = engine)
Session = sqlalchemy.orm.sessionmaker(bind = engine, autoflush = True, autocommit = True)

slb_table = sqlalchemy.Table("slb_test", metadata, autoload=True, autoload_with=engine)

session = Session()

query = slb_table.select().order_by(slb_table.c.id)
for item in session.execute(query):
    print item
session.close()

Obviously adding some test for value type in _LOBMixin would help, but most likely there is some deeper problem below.

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