If I have a persistent instance in my session and I call merge on an
object that equates to that instance, some attributes (it seems those
that aren't explicitly set on the merging instance) are expired and
get re-queried the next time they are referenced.
We will be supporting remote databases and I may be iterating at some
points over hundreds or more records that I've already queried and are
persistent, so I wish these wouldn't expire.
Is this behavior intentional?
Version 0.5.8
For example, see the output from this simple script:
=================================
from sqlalchemy import *
from sqlalchemy.orm import *
engine = create_engine('postgres://kb:k...@localhost:5444/kb',echo=True)
metadata = MetaData()
Session = sessionmaker(bind=engine)
DBSession = Session()
order_table = Table("orders", metadata,
Column("orderid", Unicode, primary_key=True),
Column("type", Unicode)
)
class Order(object):
pass
order_mapper = mapper(Order, order_table)
#metadata.create_all(engine)
o=Order()
o.orderid=u'SALE25863'
DBSession.query(Order).get(u'SALE25863')
merged=DBSession.merge(o)
merged.orderid
merged.type #<------------At this point, type is expired
################
==================================================
output:
==================================================
>>> from sqlalchemy.orm import *
>>>
>>> engine = create_engine('postgres://kb:k...@localhost:5444/kb',echo=True)
>>> metadata = MetaData()
>>> Session = sessionmaker(bind=engine)
>>> DBSession = Session()
>>>
>>> order_table = Table("orders", metadata,
... Column("orderid", Unicode, primary_key=True),
... Column("type", Unicode)
... )
>>>
>>>
>>> class Order(object):
... pass
...
>>> order_mapper = mapper(Order, order_table)
>>>
>>> #metadata.create_all(engine)
...
>>> o=Order()
>>> o.orderid=u'SALE25863'
>>>
>>> DBSession.query(Order).get(u'SALE25863')
2010-02-20 05:55:11,859 INFO sqlalchemy.engine.base.Engine.0x...2cd0
BEGIN
2010-02-20 05:55:11,863 INFO sqlalchemy.engine.base.Engine.0x...2cd0
SELECT orders.orderid AS orders_orderid, orders.type AS orders_type
FROM orders
WHERE orders.orderid = %(param_1)s
2010-02-20 05:55:11,864 INFO sqlalchemy.engine.base.Engine.0x...2cd0
{'param_1': 'SALE25863'}
<__main__.Order object at 0x14ee710>
>>>
>>>
>>> merged=DBSession.merge(o)
>>>
>>> merged.orderid
u'SALE25863'
#################################
>>> merged.type #<------------At this point, type is expired ################
2010-02-20 05:55:11,870 INFO sqlalchemy.engine.base.Engine.0x...2cd0
SELECT orders.type AS orders_type
FROM orders
WHERE orders.orderid = %(param_1)s
2010-02-20 05:55:11,870 INFO sqlalchemy.engine.base.Engine.0x...2cd0
{'param_1': 'SALE25863'}
u'SAL'
>>>
>>>
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