On Tue, 2008-11-18 at 07:09 -0800, Nicola Murino wrote:
> Hi all,
>
> I read a lot of documentation about caching queryset but seems nothing
> is useful for my purpose:
>
> I have to load a treeview and so perform virtually infinite recursion,
> I want to minimize database access, here is my simplified model
>
> class Nodes(models.Model):
> name = models.CharField(max_length=255)
> sublivello_di = models.ForeignKey('self', blank=True, null=True,
> related_name='sublivelli_set')
>
> class ObjectType1(models.Model):
> ...
> ...
> node=models.ForeignKey(Nodes)
>
>
> class ObjectType2(models.Model):
> ...
> ...
> node=models.ForeignKey(Nodes)
>
>
> and so on.
>
> I would like to select all the object before recursion, for example:
>
> allnodes=Nodes.objects.select_related('sublivello_di').all()
> allobject1=ObjectType1.objects.select_related().all()
>
> however when I do some filtering django hits the database, however all
> the objects are already fetched, I need only a subset of this.
What do you mean "when you do some filtering"? Querysets only access the
database when you access the individual results inside the queryset. So,
for example, neither of the above two statements cause any database
operations. It's only when you try to work with the data in allnodes or
allobject1 that the database will be accessed.
So if you're adding extra filters to those querysets, you can happily do
so and it won't cause any database accesses (again, until you use the
objects' data).
If you could provide a short code fragment showing what you mean by
filtering (of the query in the view? At the template level?), that might
help.
Also, how are you determining that the database is being accessed each
time?
Regards,
Malcolm
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