#django

can you give me some guideliness what to look for

Sylar427: perhaps start with the django docs on validation

thanks shangxiao

Hi, I use the queryset.values() method to implement a group-by functionality. Values however additionaly changes the return value from object to dict-based return values. Is there a way to separate both?

hmm?

hmm

Schrostfutz: that is the intended purpose of values()

Schrostfutz: why do you want to group by? are you doing aggregation?

just playing around looks like values() doesn't effect a group by… perhaps you're doing something else to the queryset?

I am trying to use prefetch_related to prefetch a reverse relation through a foreign key like this: things = Thing.objects.filter(...).prefetch_related('foo__bar_set'), but even though I see the prefetch queries being performed, subsequent calls like things[0].foo.bar_set.get() result in further queries. What's weird is that things[0].foo.bar_set.all()[0] does not!

hylje, shangxiao: I reread the documentation, now it is more clear to me.

Fish-Face: seems expected to me, get() would be supplied with a different set of criteria right?

shangxiao: how can filter() help me out here? :)

i cant find anything useful in docs

Hi. I followed this middleware to make a login required for all pages: http://onecreativeblog.com/post/59051248/django...

.get() always resolves into a new query

I've put this middleware in myproject/myapp/middleware/login_required_middleware.py and put this in my settings.py MIDDLEWARE:

emotionfolio: https://docs.djangoproject.com/en/1.11/topics/d...

shangxiao: I am not sure how get() works under the hood but I don't see that it's changing the query in the docs

emotionfolio: if you put the new max in an F() perhaps that'll work?

'myproject.middleware.login_required_middleware.LoginRequiredMiddleware'

Now I get this error when starting the dev server:

fub: which version of Django are you using?

TypeError: object() takes no parameters

TypeError: object() takes no parameters

sorry for the duplicate

FunkyBob: one second

1.11.1

ok

that's an old article, using the old interface for middleware

and ytou've put it in the list of new interface middleware

one tick

oh, okay

so I need to find a different middleware snippet?

just need to update it :)

shangxiao: .filter(F(Max('free'))) u mean this?

no, that's not what the doc link suggests :P

didnt see the link :)

FunkyBob: works, awesome. thanks!

shangxiao:

.filter(free=F('free'))?

nah, that will not do the work

=/

you're not even trying now

(you haven't used max there)

i cant get how this orm works..

it is so simple queryset in raw sql

try what you just pasted but put a max, you may need add it to the annotate() as an extra column

i have tried this way

it tells that free is an aggregate

ok let me play around

it looks like queryset.get() first does queryset.filter() but I can't tell whether that does anything with no args

emotionfolio: oh hang on i see what you're trying to do, i think misread your original question

emotionfolio: if you're after a subquery then you can do that with filter() btw

but basically you want to match a datacenter record per max in the aggregate right?

is django-webpack-loader good stuff? other takers for rigging up fancy frontends?

I want to show a link in a template only if request.user.profile.role == 'admin'. Because I have to check this a few times, is there a convenient way to do this or should I write a custom template filter?

fub: write a filter, annotate the request object, or include the property in the context

shangxiao: sorry, i was afk.. Basicly yes, i need to get max free and group by datacenter

so i get most free server on datacenter

Fish-Face: pretty much all queryset methods will first create a clone of the queryset, which won't have any cached values. I think the only exceptions are .count() and exists(), which will use the cache if it's available

Fish-Face: what do you mean with "annotate the request object" ?

hello

can someone help me with an error?

fub: I mean in your view, or in the middleware, you could say "request.admin = (request.user.profile.role == 'admin')"

Fish-Face: and then {% if request.admin %}...{% endif %} in the template?

yup

if you want to do that a lot then either do that in a middleware, or instead write a contextmanager to do something similar but add 'admin' to the context.

Fish-Face: Is something like this also possible? {% if is_org_admin(user) %}...{% endif%} ?

Thats not a "template filter", more like a function, right?

knbk: even .all() returns a clone, but it still works with prefetch_related...

fub: django templates don't support 'functions' like that, filters yes but they're kinda limited

yeah you're getting out of the scope of template stuff

jinja can let you stick fancy logic in your templates if you like

mh no, I want to stick with the default template language

so how would my filter look like without using a function? {% if user|is_org_admin %} ?

yeah

filters are simple one or two argument functions

all right, then I will go for this. I think its the simplest solution :)

thanks

np

?

exit

:wq

Fish-Face: all() on a related manager does not create a clone if there are prefetched objects, but all() on a queryset does.

knbk: ahh gotcha. and presumably get() on the manager still does make a clone

Fish-Face: all methods other than .all() on a related manager are proxied to a queryset and will create a clone

I see

shame the docs skip over that point! at least in the documentation on prefetch_related

it's a bit nuts-and-bolts

mm

shangxiao: hello? :)

emotionfolio: hi!

what's up?

shangxiao: we were talking about group by and max hehe

i dont have any ideas..

i believe you suggested using a subquery as well, trying filtering by subquery expression

there are a few sql tricks to get the datacenter record from a group by

distinct on is one of them iirc?

oh that's using distinct on with order by to get a max

looks like distinct() does DISTINCT ON with postgres too: https://docs.djangoproject.com/en/1.11/ref/mode...