Re: Filtering for an object that is modified in memory loses those modifications?

2010-04-23 Thread Margie Roginski 
Thanks for the clarification Skylar and Bill.  That all makes sense.

Margie

On Apr 23, 12:48 pm, Bill Freeman  wrote:
> This is correct behavior.  You do not have a handle on a db row.
> You have a reference to an instance of a python class whose
> attributes contain data copied from the (set of foreign key and/or
> join table related )db row(s).  Filter is a means of preparing a new
> query to run against the db.  When that query is executed (the
> filter return is evaluated) a new collection of python class instances
> is created and populated from what the db returns for the query.
> There is no awareness that you still have a reference to some other
> instance.  The new instance of the class for the particular row will
> have been populated only from the databases.  Changes to that
> other instance are private to the software holding a reference to it
> unless and until you call its save() method -- the save method of
> some other instance such as the one from the latter query, won't
> do --  at which time the ORM will compose and execute an update
> query on the database to set the fields in the row according to the
> attribute values of the instance.
>
> Bill
>
> On Fri, Apr 23, 2010 at 3:15 PM, Margie Roginski
>
>
>
>  wrote:
> > I have a situation where I have a handle to a db object and I've
> > modified a field in it.  Then I later end up executing a filter that
> > finds that same object (among others) and saves all of the objects it
> > finds.  In this situation the modified fields do not get saved out.
> > It's like the filter is getting the object directly from the database,
> > as opposed to getting the object that is in memory and modified (but
> > not yet saved).
>
> > Is this the expected behavior?
>
> > Margie
>
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Re: Filtering for an object that is modified in memory loses those modifications?

2010-04-23 Thread Bill Freeman 
This is correct behavior.  You do not have a handle on a db row.
You have a reference to an instance of a python class whose
attributes contain data copied from the (set of foreign key and/or
join table related )db row(s).  Filter is a means of preparing a new
query to run against the db.  When that query is executed (the
filter return is evaluated) a new collection of python class instances
is created and populated from what the db returns for the query.
There is no awareness that you still have a reference to some other
instance.  The new instance of the class for the particular row will
have been populated only from the databases.  Changes to that
other instance are private to the software holding a reference to it
unless and until you call its save() method -- the save method of
some other instance such as the one from the latter query, won't
do --  at which time the ORM will compose and execute an update
query on the database to set the fields in the row according to the
attribute values of the instance.

Bill

On Fri, Apr 23, 2010 at 3:15 PM, Margie Roginski
 wrote:
> I have a situation where I have a handle to a db object and I've
> modified a field in it.  Then I later end up executing a filter that
> finds that same object (among others) and saves all of the objects it
> finds.  In this situation the modified fields do not get saved out.
> It's like the filter is getting the object directly from the database,
> as opposed to getting the object that is in memory and modified (but
> not yet saved).
>
> Is this the expected behavior?
>
> Margie
>
> --
> You received this message because you are subscribed to the Google Groups 
> "Django users" group.
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> For more options, visit this group at 
> http://groups.google.com/group/django-users?hl=en.
>
>

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Re: Filtering for an object that is modified in memory loses those modifications?

2010-04-23 Thread Skylar Saveland 
Yes.  The filter method returns a queryset which is a lazy database
object that will query the database to get the queryset.  You would
have to save the object for the queryset to return it.  You could
however get all of the objects which are not your select objects

 
MyModel.objects.exclude(pk__in=iterable_of_in_memory_pks_not_to_be_returned)

On Apr 23, 3:15 pm, Margie Roginski  wrote:
> I have a situation where I have a handle to a db object and I've
> modified a field in it.  Then I later end up executing a filter that
> finds that same object (among others) and saves all of the objects it
> finds.  In this situation the modified fields do not get saved out.
> It's like the filter is getting the object directly from the database,
> as opposed to getting the object that is in memory and modified (but
> not yet saved).
>
> Is this the expected behavior?
>
> Margie
>
> --
> You received this message because you are subscribed to the Google Groups 
> "Django users" group.
> To post to this group, send email to django-us...@googlegroups.com.
> To unsubscribe from this group, send email to 
> django-users+unsubscr...@googlegroups.com.
> For more options, visit this group 
> athttp://groups.google.com/group/django-users?hl=en.

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Filtering for an object that is modified in memory loses those modifications?

2010-04-23 Thread Margie Roginski 
I have a situation where I have a handle to a db object and I've
modified a field in it.  Then I later end up executing a filter that
finds that same object (among others) and saves all of the objects it
finds.  In this situation the modified fields do not get saved out.
It's like the filter is getting the object directly from the database,
as opposed to getting the object that is in memory and modified (but
not yet saved).

Is this the expected behavior?

Margie

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