Hi Rajesh,
Thanks for your help so far - that definitely improved things
somewhat!
However, I'm still having a slight problem. When I pass
Item.objects.get(id=id) into the serializers.serialize( ... )
function, it tells me that the Item is not iterable (this is why I was
originally using filter() in the first place, in order to make it
iterable). So a second ago I just tried encasing the
Item.objects.get(id=id) into a list [] and this worked. However, that
seems like a bit of a hack, or even that I'm not using the function
correctly. Is there a better approach to take here?
Just so you know, I'm using Django v1.0.
Thanks again,
Mike.
On Sep 30, 6:04 pm, Rajesh Dhawan <[EMAIL PROTECTED]> wrote:
> On Sep 30, 12:46 pm, "[EMAIL PROTECTED]"
>
> <[EMAIL PROTECTED]> wrote:
> > Hi guys,
>
> > I was wondering if somebody could help me with deserialization.
>
> > I'm currently trying to cache the result of a database query using a
> > JSON serializer in (what I assume to be) the standard fashion:
>
> > -----------
> > def cache_query(id):
> > cache_key = "cache_key_" % id
> > item = cache.get(cache_key)
>
> > if item is None:
> > item_obj = Item.objects.filter(id=id)
>
> Realize that item_obj here is really a QuerySet because filter()
> always returns a QuerySet even if this query matches just one row.
>
> Since you're caching only one model instance, you could simply replace
> the above with:
>
> item_obj = Item.objects.get(id=id)
>
> Then when you deserialized this cached item_obj, it won't call the DB.
>
>
>
> > item = serializers.serialize("json", item_obj,
> > ensure_ascii=False)
> > cache.set(cache_key, item, 30) # I've just chosen a random
> > number for seconds here
> > item_deserial = list(serializers.deserialize("json", item))
> > [0].object
>
> > return item_deserial
> > ------------
>
> > It seems like the deserializer is talking to the database in order to
> > reconstruct the queryset. I may be wrong on this, but commenting out
> > the deserializer line reduces the number of queries by the amount I'd
> > expect if it was not talking to the database. It's obviously quite
> > helpful reconstructing a queryset (as you can follow foreign key
> > relationships etc), but is there anyway to purposely prevent it from
> > recontacting the database? Is it even contacting the database?
>
> > I'd really like to minimise the number of queries and I don't need the
> > full flexibility of a Queryset, a dictionary of the values would be
> > more than adequate for what I'm doing, which I could extract from the
> > serialized values (after a bit of eval/str fun!).
>
> You can use the values() method on a QuerySet to get dictionaries of
> rows. You can even choose which fields you are interested in. Then,
> run a list() call on such a queryset and cache that result.
>
> See documentation of QuerySet.values()
> here:http://docs.djangoproject.com/en/dev//ref/models/querysets/#values-fi...
>
>
>
> > If somebody could point out any obvious errors with my code, I'd be
> > really grateful! I'm very new the caching, so any pointers would be
> > great.
>
> -RD
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Django users" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/django-users?hl=en
-~----------~----~----~----~------~----~------~--~---
