[sqlalchemy] SQLAlchemy, PostgreSQL and custom types

[Orca]

I have a problem with updating custom types in SQLAlchemy, issue is
that when I modify object attributes they are not detected as
modified. E/g:

# python class to work with
class BDelta(object):
    def __init__(self):
        self.id = None
        self.flags = None
        self.deltas = []

    def __repr__(self):
        deltas = ", ".join(["%s" % delta for delta in self.deltas])
        res = '(%s, %s, ARRAY[%s])::bdelta' % (self.id, self.flags,
deltas)
        return res

# SQLAlchemy type representing BDelta
class PGBDelta(sqltypes.TypeEngine):
    def copy_value(self, value):
        if value is None:
            return None
        else:
            return deepcopy(value)

    def compare_values(self, x, y):
        print "compare_values  - %s %s" % (repr(x), repr(y))
        return x == y

    def bind_processor(self, dialect):
        def process(value):
            return value
        return process

    def result_processor(self, dialect):
        def process(value):
            return value
        return process

    def get_col_spec(self):
        return 'bdelta'

Table definition:

tmptbl_table = sa.Table("tmptbl", meta.metadata,
                          sa.Column("id", sa.types.Integer,
primary_key = True),
                          sa.Column("test_ints", PGArray
(sa.types.Integer)),
                          sa.Column("bdarr", PGArray(PGBDelta))
    )


class Tmptbl(object):
    @staticmethod
    def Get(tid):
        return meta.Session.query(Tmptbl).get(tid)

orm.mapper(Tmptbl, tmptbl_table)


Test function:

def test_func():
    x = Tmptbl.Get(108)
    x.bdarr[0].id = randint(0, 100)
    meta.Session.flush()
    meta.Session.commit()

Problem is that nothing is flushed in that case, because
x._sa_instance_state.mutable_dict['bdarr'] and
x._sa_instance_state.dict['bdarr'] are the same list of BDelta objects
and when I change property of one of those objects, changes are made
to both dict and mutable_dict, so SQLAlchemy doesn't find any
difference when flushing.

Question is: is there any way to fix that, make full copy of values on
"get" or something.
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