Hi James, I've read the docs but I still couldn't figure it out. My queryset works great in production, I'm trying to optimize it because our pageloads are too slow. I know how to use querysets in Django pretty well, I just don't know how to use `Prefetch`.
Can you give me the solution for the simplified example I gave? This might help me figure out what I'm not understanding. One thing that might be unclear with the example I gave, is that I meant I want to get a queryset for `Desk` where every desk has an attribute names `favorite_or_nearby_chairs` which contains the queryset of chairs that I desrcibed, prefetched. Thanks, Ram. On Wed, Feb 25, 2015 at 11:18 PM, James Schneider <[email protected]> wrote: > I assume that you are talking about the select_related() and > prefetch_related() queryset methods? > > https://docs.djangoproject.com/en/1.7/ref/models/querysets/#select-related > > https://docs.djangoproject.com/en/1.7/ref/models/querysets/#prefetch-related > > Both of those sections have excellent examples, and detail what the > differences are (primarily joins vs. separate queries, respectively). > > For better help, you'll need to go into more detail about the queries you > are trying to make, what you've tried (with code examples if possible), and > the results/errors you are seeing. > > In general, I would try to get an initial queryset working and gathering > the correct results first before looking at optimizations such as > select_related(). Any sort of pre-fetching will only confuse the situation > if the base queryset is incorrect. > > -James > > On Wed, Feb 25, 2015 at 12:05 PM, cool-RR <[email protected]> wrote: > >> Hi guys, >> >> I'm trying to solve a problem using the new `Prefetch` but I can't figure >> out how to use it. >> >> I have these models: >> >> class Desk(django.db.models.Model): >> pass >> >> class Chair(django.db.models.Model): >> desk = django.db.models.Foreignkey('Desk', related_name='chair',) >> nearby_desks = django.db.models.ManyToManyField( >> 'Desk', >> blank=True, >> ) >> >> I want to get a queryset for `Desk`, but it should also include a >> prefetched attribute `favorite_or_nearby_chairs`, whose value should be >> equal to: >> >> Chair.objects.filter( >> (django.db.models.Q(nearby_desks=desk) | >> django.db.models.Q(desk=desk)), >> some_other_lookup=whatever, >> ) >> >> Is this possible with `Prefetch`? I couldn't figure out how to use the >> arguments. >> >> >> Thanks, >> Ram. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Django users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at http://groups.google.com/group/django-users. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/django-users/46d9fdb7-c008-4496-acda-ac7cb30b4a89%40googlegroups.com >> <https://groups.google.com/d/msgid/django-users/46d9fdb7-c008-4496-acda-ac7cb30b4a89%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> For more options, visit https://groups.google.com/d/optout. >> > > -- > You received this message because you are subscribed to a topic in the > Google Groups "Django users" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/django-users/EuPduHjSNos/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/django-users. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-users/CA%2Be%2BciVk7_6VBDoBE-qjLBwrBxiNeVdP6-fwwnOXV%3DvSA3HnCw%40mail.gmail.com > <https://groups.google.com/d/msgid/django-users/CA%2Be%2BciVk7_6VBDoBE-qjLBwrBxiNeVdP6-fwwnOXV%3DvSA3HnCw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/CANXboVY7ffbsLKi5hCaNkGUNz%2B_A2vO-PueQfCGhB%3DJoKOERnw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
