Just when I thought I understood the Session object, I found this
behavior:
( I am starting to think about concurrency and locking )
I create 2 sessions, and load each with the same ( persisted ) object.
The objects appear to be independent, even after both sessions have
flushed,
but when I commit one session, it suddenly picks up the change from
the other session!
This is confusing me!
What is going on here?
( my business object is a "Policy", and column "test" is not the PK )
class PolicyNotFoundException(Exception):
pass
def open_policy(key):
session = Session()
try:
policy = session.query(Policy).filter_by(key=key).all()[0]
return policy, session
except:
raise PolicyNotFoundException
def test_concurrent_updates():
policy1,session1 = open_policy('NICK')
policy2,session2 = open_policy('NICK') # retrieves on pk...gets
same record
assert( policy1 != policy2 )
assert( session1 != session2 )
assert( policy1 in session1 )
assert( policy1 not in session2 )
assert( policy2 in session2 )
assert( policy2 not in session1 )
policy1.test = 'ONE'
session1.flush()
policy2.test = 'TWO'
session2.flush()
assert( policy1.test == 'ONE' ) # not affected by flush of session
2
session1.commit()
assert( policy1.test == 'TWO' ) # really?
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