On Sep 22, 2010, at 5:17 PM, Michael Hipp wrote:
> On 9/22/2010 11:21 AM, Michael Hipp wrote:
>
>> new = Car()
>> new.id_ = old.id_
>> new = sess.merge(new)
>> new.auction = old.auction # do this *after* merge
>> sess.commit()
>>
>> This seems to work and ...
>
> Bah. I spoke too soon - it just doesn't throw an exception.
that absolutely does what you tell it (guess thats not what you want). Make
sure Car's init is:
def __init__(self, lane=None, make='', auction=None):
self.lane = lane
self.make = make
if auction is not None:
self.auction = auction
then:
new = Car()
new.id_ = old.id_
new.lane = old.lane
new = sess.merge(new)
new.auction = old.auction
sess.commit()
SQL:
UPDATE cars SET make=? WHERE cars.id_ = ?
('', 1)
> But without explicitly setting every field to its default value, the session
> thinks nothing has changed and the UPDATE leaves most of the fields untouched.
>
> Anyway, it appears I need a new approach to empty/blank a record. Options I
> can think of are:
Here's the problem. The term "a blank record" is meaningless. You have to
spell that out explicitly, on every class that has a concept of "blank".
Class A might consider fields x, y, z but not q, p, r to be part of "blank",
class B has some totally different idea. Whether or not database fields have a
"default" configured at the database level or table metadata level is also an
artificial constraint...sure flip through table.c and look at default
/server_default if you want that, but I've never written an app that had rules
even that simplistic.
Trying to make other tools guess this for you seems to be taking up days of
your time - whereas a simple def set_myself_blank(self) method OTOH would take
30 seconds.
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