[sqlalchemy] Re: Default value for objects' attributes
On 30 juil, 22:33, Michael Bayer [EMAIL PROTECTED] wrote: yes, figured that. The issues with this are that it would not be consistently available; it could only work for Python-side defaults, and could also only work for defaults that do not require an ExecutionContext Ah, consistency, this is the word I was looking for :) Also if you really need the False before any flush occurs, you might want to define that in the __init__ method of your mapped class as well. If you create an external function called my_table_default (), the same function can be placed within your Table def as well as your class's __init__ method. Ok, I think we will use something like that : class Test(object): def __init__(self): self.test_value = self.c.test_value.default.arg ... And so on (maybe a wrapper around self.c.test_value.default.arg, to make it shorter). Thanks a lot for your answers ! --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Default value for objects' attributes
On Jul 30, 2007, at 7:29 PM, Paul Johnston wrote: Hi, The problem is that creating a new object from class Test doesn't set the default value for attributes : Seems like a good time to bring up a slightly related problem. If you modify an object in a function providing a default value, the object is not flushed (unless you do that manually). Ideally flushing would detect this and cope with it. If defaults were supplied at constructor time, we would get that behaviour with no further work. not sure i understand the scenario here, could you illustrate ? --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Default value for objects' attributes
Hi, Seems like a good time to bring up a slightly related problem. If you modify an object in a function providing a default value, the object is not flushed (unless you do that manually). not sure i understand the scenario here, could you illustrate ? I've put a bit more explanation and a test case on ticket #703. I had a look at fixing it, but it seems like a tough one. Paul --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Default value for objects' attributes
On Jul 31, 2007, at 11:30 AM, Paul Johnston wrote:
Hi,
Seems like a good time to bring up a slightly related problem. If
you
modify an object in a function providing a default value, the
object is not flushed (unless you do that manually).
not sure i understand the scenario here, could you illustrate ?
I've put a bit more explanation and a test case on ticket #703. I
had a
look at fixing it, but it seems like a tough one.
ok that exactly cannot be fixed, and i would suggest that you dont
use an ORM mapped class as a default value generator. The reason it
cannot is because once the flush() is proceeding, everything which is
to be inserted/updated/deleted has been laid out and placed into a
queue to be executed. Any changes to instrumented attributes which
occur *within* the flush is not going to get picked up - that train
has already left the station.
the way to do this pattern is to use straight SQL instead (note
however, the 'ctx' variable requires 0.4):
seq = Table('seq', m,
Column('seq', String(50), primary_key=True),
Column('nextval', Integer))
def newid(ctx):
id = ctx.connection.execute(select([seq.c.nextval],
seq.c.seq=='tbl', for_update=True)).scalar()
ctx.connection.execute(seq.update(values=[seq.c.nextval :
seq.c.nextval +1]))
return hex(id)
This way you also get fine-grained control over the seq table's locking.
However I do need to commit something to make that work so that will
be the ticket's resolution.
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[sqlalchemy] Re: Default value for objects' attributes
Cant reproduce. Heres a test script which runs fine for me with PG 8.1:
from sqlalchemy import *
metadata = MetaData('postgres://scott:[EMAIL PROTECTED]/test')
test = Table('test', metadata,
Column('id', Integer, primary_key=True),
Column('test_value', Boolean, default=False, nullable=False)
)
metadata.create_all()
class Test(object):pass
test_mapper = mapper(Test, test)
t = Test()
sess = create_session()
sess.save(t)
sess.flush()
print t.test_value
did you forget to flush() ?
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[sqlalchemy] Re: Default value for objects' attributes
your _own_ ctor, or something around mapperExtension? On Monday 30 July 2007 21:26:44 Jonathan Ballet wrote: No, after a flush(), everything is fine. However, I would like to have the default value _before_ flush()-ing. Hmm, after thinking about it a few more minutes, it would be a bit restrictive, since it will work only for 'scalar' values :/ --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Default value for objects' attributes
On Jul 30, 2007, at 2:26 PM, Jonathan Ballet wrote: No, after a flush(), everything is fine. However, I would like to have the default value _before_ flush()-ing. Hmm, after thinking about it a few more minutes, it would be a bit restrictive, since it will work only for 'scalar' values :/ yes, figured that. The issues with this are that it would not be consistently available; it could only work for Python-side defaults, and could also only work for defaults that do not require an ExecutionContext (i.e. the full set of parameters being passed to the INSERT statement). The usage model with SA, and especially in 0.4, is that data can be flushed anytime...no need to wait for some special time to flush. with that model, your defaults are availble in all cases the way youd want them. Also if you really need the False before any flush occurs, you might want to define that in the __init__ method of your mapped class as well. If you create an external function called my_table_default (), the same function can be placed within your Table def as well as your class's __init__ method. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Default value for objects' attributes
Hi, The problem is that creating a new object from class Test doesn't set the default value for attributes : Seems like a good time to bring up a slightly related problem. If you modify an object in a function providing a default value, the object is not flushed (unless you do that manually). Ideally flushing would detect this and cope with it. If defaults were supplied at constructor time, we would get that behaviour with no further work. Paul --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
