Hello,
I've been trying to do unit testing with SQLAlchemy and PostgreSQL. In
my model/tables I have two entities state and country, state has a
foreign key relating to country (no problems there).
In my setUp() method I call create_all() for my metadata while in
tearDown() I call drop_all(). The problem that I was detecting is that
it nosetests frozes when is dropping the "state" table after running
the following test:
def test_country_create_orm(self):
new_country = Country('Country')
id = new_country.id
session = Session()
session.add(new_country)
session.commit()
#session.flush()
test_country = session.query(Country).get(id)
assert test_country.id == id
The Session class is generated with sessionmaker() in the following
way (where engine is the parameter that is passed on to init_model of
Pylons, however I tested the same conditions with create_engine):
sm = orm.sessionmaker(bind=engine, autoflush=True, autocommit=False)
Session = orm.scoped_session(sm)
I chased the problem through a debugger down onto the implementation
of do_execute for the cursor for the Connection object for PostgreSQL,
after which I strace'd it and discovered that it was being hold on the
poll(2) system call.
I don't know if I'm doing something wrong but I discovered that my
unit tests work if I configure my Session class as:
sm = orm.sessionmaker(bind=engine, autoflush=True, autocommit=True)
Session = orm.scoped_session(sm)
And flush()ing instead of commit()ing. What also works is that if
instead of doing the query
test_country = session.query(Country).get(id)
I do this:
count = session.query(Country).count()
This doesn't appear to be restricted to the drop_all() method of
MetaData. If I import my Table object that represents my "State" table
and drop it directly it also freezes:
from myapp.model.table import state
state.drop() # freezes
I have tested this issue with Python 2.6.6, SQLAlchemy 0.6.5 and
0.6.6, psycopg2 2.3.1 and 2.3.2 and PostgreSQL 8.4.5.
Any insights?
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