Schema qualified tables with SQLAlchemy, SQLite an

问题:

I have a Pylons project and a SQLAlchemy model that implements schema qualified tables:

class Hockey(Base):
    __tablename__ = "hockey"
    __table_args__ = {'schema':'winter'}
    hockey_id = sa.Column(sa.types.Integer, sa.Sequence('score_id_seq', optional=True), primary_key=True)
    baseball_id = sa.Column(sa.types.Integer, sa.ForeignKey('summer.baseball.baseball_id'))

This code works great with Postgresql but fails when using SQLite on table and foreign key names (due to SQLite's lack of schema support)

sqlalchemy.exc.OperationalError: (OperationalError) unknown database "winter" 'PRAGMA "winter".table_info("hockey")' ()

I'd like to continue using SQLite for dev and testing.

Is there a way of have this fail gracefully on SQLite?

回答1:

I'd like to continue using SQLite for dev and testing.

Is there a way of have this fail gracefully on SQLite?

It's hard to know where to start with that kind of question. So . . .

Stop it. Just stop it.

There are some developers who don't have the luxury of developing on their target platform. Their life is a hard one--moving code (and sometimes compilers) from one environment to the other, debugging twice (sometimes having to debug remotely on the target platform), gradually coming to an awareness that the gnawing in their gut is actually the start of an ulcer.

Install PostgreSQL.

When you can use the same database environment for development, testing, and deployment, you should.

Not to mention the QA team. Why on earth are they testing stuff they're not going to ship? If you're deploying on PostgreSQL, assure the quality of your work on PostgreSQL.

Seriously.

回答2:

I'm just a beginner myself, and I haven't used Pylons, but...

I notice that you are combining the table and the associated class together. How about if you separate them?

import sqlalchemy as sa
meta = sa.MetaData('sqlite:///tutorial.sqlite')
schema = None
hockey_table = sa.Table('hockey', meta,
                      sa.Column('score_id', sa.types.Integer, sa.Sequence('score_id_seq', optional=True), primary_key=True),
                      sa.Column('baseball_id', sa.types.Integer, sa.ForeignKey('summer.baseball.baseball_id')),
                      schema = schema,
                    )

meta.create_all()

Then you could create a separate

class Hockey(Object):
    ...

and

mapper(Hockey, hockey_table)

Then just set schema above = None everywhere if you are using sqlite, and the value(s) you want otherwise.

You don't have a working example, so the example above isn't a working one either. However, as other people have pointed out, trying to maintain portability across databases is in the end a losing game. I'd add a +1 to the people suggesting you just use PostgreSQL everywhere.

HTH, Regards.