Hi group,
I have a question about Oracle CLOBs.
I expect to be able to manage all 3 different LOB column states:
(a) Populated
(b) Empty
(c) NULL
First of all: is it my expectation correct?
I'm in process of upgrading to SqlAlchemy 0.6.9 and this seems (to me)
no more possible.
Here it is how to build 3 examples (one for each column state).
# ------------------------------
# SQL for manual table creation:
DROP TABLE t_tmp_sqla_upgrade;
CREATE TABLE t_tmp_sqla_upgrade (
id NUMBER (20) not null,
text CLOB
);
# ------------------------------
# Python code:
from sqlalchemy import MetaData, Table, Column, Integer, Text,
create_engine
from sqlalchemy.orm import mapper, sessionmaker
metadata = MetaData()
table = Table('t_tmp_sqla_upgrade', metadata,
Column('id', Integer, primary_key=True),
Column('text', Text())
)
class TmpTableEntity(object):
pass
mapper(TmpTableEntity, table)
kwargs = {}
kwargs['encoding'] = 'utf-8'
engine = create_engine(u"oracle+cx_oracle://user:pwd@db", **kwargs)
Session = sessionmaker(bind=engine, autoflush=False)
def createItem(session, text):
e = TmpTableEntity()
e.id = 1
e.text = text
session.add(e)
session.commit()
session.expunge_all()
return e
def readItem(session, id):
return
session.query(TmpTableEntity).filter(TmpTableEntity.id==id).one()
session = Session()
# 3 cases (setup and teardown is needed for each case)
# Case (a): some text (OK)
text = u'some plain ascii text'
item = createItem(session, text)
rItem = readItem(session, 1)
assert rItem.text == text
# Case (b): empty text (KO)
text = u''
item = createItem(session, text)
rItem = readItem(session, 1)
assert rItem.text == None
# But I expect: assert rItem.text == u''
# since this is a CLOB field and not a VARCHAR2 one.
# Case (c): null text (OK)
text = None
item = createItem(session, text)
rItem = readItem(session, 1)
assert rItem.text == None
Thank you for your time,
Francesca
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