programmer.py wrote:
> Hi. I've been working on some unittests for a pylons application.
> Part of that testing involves adding data to the database, submitting
> a request through the paster testing framework and examining the
> response.
>
> I use two separate sessions for unittests. One is generated by the
> pylons application itself and the other is created for the unittest.
> Whenever I add data in the unittest session, it is not seen by the
> pylons application. This simple script below demonstrates whats
> happening during my tests. (Or at least what I think is happening).
>
> Is there any way around this? The only alternative I see is using the
> same session as the pylons application. But I've run into other
> issues when I try to do that.
>
> The output from the script below is ->
>
> 0
> 10
> 0
when I run it the output is:
zzzeek-3:sqlalchemy classic$ python test.py
0
10
10
This is because by default the engine is MyISAM and there's no transaction
isolation between the two connections.
However, if I change the table to use InnoDB, then the transaction
isolation kicks in and we get the expected:
zzzeek-3:sqlalchemy classic$ python test.py
0
10
0
the second connection gets zero because the transaction is referencing
what's already been selected (i.e. no phantom reads). Rolling back s2
before reselecting again gives us:
zzzeek-3:sqlalchemy classic$ python test.py
0
10
10
>
> # Begin python script
> import sys
> from sqlalchemy.ext.declarative import declarative_base
> from sqlalchemy import Column, Integer, String, create_engine
> from sqlalchemy.orm import sessionmaker
>
> Base = declarative_base()
>
>
> class SimpleTest(Base):
> __tablename__ = 'simpletest'
>
> id = Column(Integer, primary_key=True)
> s1 = Column(String(255))
>
>
> def main():
> engine1 = create_engine('mysql://test:t...@localhost/test')
> engine2 = create_engine('mysql://test:t...@localhost/test')
> SimpleTest.metadata.create_all(engine1)
>
> # Clear out the test table.
> con = engine1.connect()
> con.execute('TRUNCATE simpletest')
>
> # Create two distinct sessions.
> s1 = sessionmaker(bind=engine1)()
> s2 = sessionmaker(bind=engine2)()
>
> # Show empty table count on session 2.
> print s2.execute('SELECT COUNT(*) FROM simpletest').scalar()
>
> # Load the database with 10 rows.
> for x in range(10):
> st = SimpleTest()
> st.s1 = str(x)
> s1.add(st)
> s1.commit()
>
> print s1.execute('SELECT COUNT(*) FROM simpletest').scalar()
> print s2.execute('SELECT COUNT(*) FROM simpletest').scalar()
>
>
> if __name__ == '__main__':
> sys.exit(main())
>
>
> Thanks,
> jw
>
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