Thanks Tom.
But with this approach -
> foo = Foo.objects.get(pk=foo_id)
> foo.field = new_value
> foo.save()
There is an extra DB call, first the the data, and then another one to
save it.
If you have the primary_key with you, only one should suffice.
I mean, when we step back and look at the whole scenario, there are
thousand consumers doing this, and each has one extra DB call. That's
pretty expensive.
On Sep 22, 11:41 am, Tom Evans <tevans...@googlemail.com> wrote:
> On Tue, 2009-09-22 at 08:13 -0700, PlanetUnknown wrote:
> > I'm sure I'm missing something simple here, since its a common flow -
>
> > 1.) e.g. model Person - has 4 fields -
> > person_id = models.AutoField(primary_key=True)
> > person_name = models.CharField(max_length=50)
> > comments = models.TextField(blank=True)
> > create_dt = models.DateTimeField(auto_now_add=True)
> > modify_dt = models.DateTimeField(auto_now_add=True)
> > class Meta:
> > unique_together = ("person_id", "person_name")
>
> > 2.) When I save a new person, everything works normal, since I'm
> > giving -
> > p1 = Person(person_id=None, person_name=personNameArg,
> > comments=pComment)
>
> > 3.) After this save is performed, I have the "person_id" of this
> > person. When someone hits save again, I do this -
>
> > p1 = Person(person_id=personIdArg, person_name=personNameArg,
> > comments=pComment)
> > where personIdArg is the earlier saved id.
>
> > I get the error - "create_dt cannot be Null", I see that dJango is
> > correctly trying to update, but since I didn't pass create_dt, it is
> > setting it to NULL in the update query.
>
> > I just want it to be left alone, since it already has a value. Is
> > there a way to tell django to not touch these fields ?
>
> > Thanks!
>
> It isn't that common; I haven't got that in any of my views.
>
> The canonical way to update an item, AFAICT, is like so:
>
> foo = Foo.objects.get(pk=foo_id)
> foo.field = new_value
> foo.save()
>
> Cheers
>
> Tom
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