I've come up with one more obstacle to setting up a project with
authentication when Oracle is the back-end.
model/auth.py sets up classes Group, User, and Permission with
autoincrement=true primary keys, like:
group_id = Column(Integer, autoincrement=True, primary_key=True)
Under Oracle, however, SQLAlchemy ignores the "autoincrement" keyword:
see
http://www.sqlalchemy.org/docs/05/reference/dialects/oracle.html#auto-increment-behavior
. Because of this, the primary key columns get no defaults, and
paster setup-app will fail against Oracle, complaining that NULLs
can't be primary keys.
Two changes fix this:
1. Replacing the autoincrement keywords, as suggested
group_id = Column(Integer, Sequence('tg_group_id_seq'),
primary_key=True)
user_id = Column(Integer, Sequence('tg_user_id_seq'),
primary_key=True)
permission_id = Column(Integer, Sequence('tg_permission_id_seq'),
primary_key=True)
2. Creating the Sequence objects doesn't actually create the sequences
in Oracle. To do that, I added this to setup_app in websetup.py:
model.metadata.create_all(bind=config
['pylons.app_globals'].sa_engine) # this was here
for tbl in model.metadata.tables.values():
for col in tbl.columns:
if col.default and isinstance(col.default, Sequence):
col.default.create(bind=config
['pylons.app_globals'].sa_engine)
After making those changes, I finally got my project setup-app'ed.
Now, having to code these changes in for Oracle projects - how much of
a pain would that be? And would it make sense to go upstream and ask
about making the changes at the SQLAlchemy level? I can't think of
any reason why SQLAlchemy itself shouldn't replace an autoincrement
keyword with a Sequence(). Then, my sequence-creating loop may as
well become a part of SQLAlchemy's metadata.create_all() itself - as
far as I can tell. ( & similar code in a table's .create(), of
course.) Or am I missing something?
Thanks as always,
--
- Catherine
http://catherinedevlin.blogspot.com/
*** PyOhio * July 25-26, 2009 * pyohio.org ***
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