[Sqlalchemy-tickets] Issue #2994: PickleType gets not updated in Database in some circumstances (zzzeek/sqlalchemy)

[Marc S. <iss...@bi...>]

New issue 2994: PickleType gets not updated in Database in some circumstances
https://bitbucket.org/zzzeek/sqlalchemy/issue/2994/pickletype-gets-not-updated-in-database-in

Marc Schlaich:

Test:


```
#!python

import logging
logging.getLogger('sqlalchemy').setLevel(logging.INFO)
logging.basicConfig()

from sqlalchemy import create_engine, Column, Integer, PickleType
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


class Test(Base):
    __tablename__ = 'test'
    id = Column(Integer, primary_key=True)
    counters = Column(PickleType)


engine = create_engine('sqlite:///:memory:')
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)


def test_update_dict():
    session = Session()
    session.add(Test(counters=[dict(counter=1)]))
    session.commit()

    t = session.query(Test).one()
    for d in t.counters:
        # it's obvious that this doesn't trigger a change in SQLA
        d['counter'] -= 1

    # try to force a change in SQLAlchemy, this should issue a
    # update query
    t.counters = list(t.counters)
    session.commit()

    t = session.query(Test).one()
    assert t.counters == [dict(counter=0)]
```

Result:


```
#!python

$ py.test sqla_test.py
============================= test session starts =============================
platform win32 -- Python 2.7.6 -- py-1.4.20 -- pytest-2.5.2
plugins: cov
collected 1 items / 1 skipped

sqla_test.py F

================================== FAILURES ===================================
______________________________ test_update_dict _______________________________

    def test_update_dict():
        session = Session()
        session.add(Test(counters=[dict(counter=1)]))
        session.commit()

        t = session.query(Test).one()
        for d in t.counters:
            # it's obvious that this doesn't trigger a change in SQLA
            d['counter'] -= 1

        # try to force a change in SQLAlchemy, this should issue a
        # update query
        t.counters = list(t.counters)
        print t.counters
        session.commit()

        t = session.query(Test).one()
>       assert t.counters == [dict(counter=0)]
E       assert [{'counter': 1}] == [{'counter': 0}]
E         At index 0 diff: {'counter': 1} != {'counter': 0}

sqla_test.py:43: AssertionError
------------------------------- Captured stdout -------------------------------
[{'counter': 0}]
------------------------------- Captured stderr -------------------------------
INFO:sqlalchemy.orm.mapper.Mapper:(Test|test) _post_configure_properties() started
INFO:sqlalchemy.orm.mapper.Mapper:(Test|test) initialize prop id
INFO:sqlalchemy.orm.mapper.Mapper:(Test|test) initialize prop counters
INFO:sqlalchemy.orm.mapper.Mapper:(Test|test) _post_configure_properties() complete
INFO:sqlalchemy.engine.base.Engine:BEGIN (implicit)
INFO:sqlalchemy.engine.base.Engine:INSERT INTO test (counters) VALUES (?)
INFO:sqlalchemy.engine.base.Engine:(<read-only buffer for 0x03971C50, size -1, offset 0 at 0x03913060>,)
INFO:sqlalchemy.engine.base.Engine:COMMIT
INFO:sqlalchemy.engine.base.Engine:BEGIN (implicit)
INFO:sqlalchemy.engine.base.Engine:SELECT test.id AS test_id, test.counters AS test_counters
FROM test
INFO:sqlalchemy.engine.base.Engine:()
INFO:sqlalchemy.engine.base.Engine:COMMIT
INFO:sqlalchemy.engine.base.Engine:BEGIN (implicit)
INFO:sqlalchemy.engine.base.Engine:SELECT test.id AS test_id, test.counters AS test_counters
FROM test
INFO:sqlalchemy.engine.base.Engine:()
===================== 1 failed, 1 skipped in 0.63 seconds =====================
```