#django

Knyght: could be that line 6 is not True when it should be, for example

subho: This is something of a major outstanding problem in python web asynchrony.

Knyght: btw, are you trying to hand out unique passwords?

moldy: kinda, they're used per game, so ayone with the password can join by like tapping it into their phone or whatever. They get rescinded when the game starts so collisions should be rare, but I still want to handle the case

Knyght: probably easier and better to use an identifier plus a password instead of trying to make the password be both

Knyght: as for the test, the problem could be in the factory...

moldy: I'm aware, but I want to make it as seemless as possible

hmm that's a thought

hmm, don't think so, at least I'm not doing anything special with it

jMyles: actually yes celery process job pool. :( spent half of my day trying various solution.

Knyght: look at the traceback...

hmm

apparently faker is calling random.choice, which is your mock

oh, ffff

thanks :/

I would probably not have caught that

you're welcome

guess that can be static anyway

or I can just hardcode it for that test I guess

subho: What type of job are you trying to do? Is it CPU-bound?

jMyles, i wanted to make django signals async. so on signal a task(insertion to two db) is added to celery .

subho: So, you can probably still do that with Celery by passing it a function that's top-level in the module instead of an instance method.

If, on the other hand, you need the context of the instance method, and your task is very CPU-light, which it sounds like it is, then (and this is sometimes heresy around these parts) you can use a thread.

subho: Twisted handles this situation very nicely and with less overhead than Celery / RabbitMQ.

subho: Here's an API for doing that with hendrix: http://hendrix.readthedocs.org/en/latest/crosst...

danielsh: take a look at https://docs.djangoproject.com/en/1.8/ref/model... ... select param

danielsh, well, this works: Host.objects.annotate(is_special=ExpressionWrapper(Case(When(user_id=152,then=1), When(~Q(user_id=152), then=0)), output_field=IntegerField()))[0].is_special

danielsh, but it's horribly contorted.

jMyles, ahh! nice! :) let me explore it. :D Thanks!

danielsh, probably better to throw some rawer SQL in there, lemme see ....

danielsh, (my Host is your Foo and my user_id is your bar_id)

dang`r`us: wtf ? :)

subho: Just make sure that your signal hook is not CPU-bound; otherwise using a thread will cause the worker performance to drop off a cliff

dodobas, yeah ... that's what I thought too.

jMyles, :P lol. i had that falling off the cliff experience when i used ffmpeg in a thread once.

danielsh, this maps to True/False not 1/0 but is way more readable: Host.objects.annotate(is_special=RawSQL("user_id=%s", (152,)))

subho: Yeah. It'll getcha. But threads are incredibly performant for network/IO bound tasks. You just need to be a lot more careful and conscientious about the intentions of your code, and that goes for many aspects of async, not just performance.

dodobas, if you can make my first example simpler, please tell me, I'm curious (basically: annotate a QS so that is_special is 1 when o.user_id=152, and 0 otherwise)

subho: We're working on a way to pass crosstown_traffic to a separate child process. A... VoodooChild process. :-)

jMyles, cool!

hey, everyone.

I have a quick question: why are some field types not created as columns in the corresponding db table? I'm on django 1.83 using MySQL 5.5.4

dang`r`us, dodobas: thanks! All those solutions are pretty much equivalent, but .extra(select=...) is tastiest to me.

efstone, tried makemigrate and migrate command?

indeed

on two separate systems

danielsh, I did not know about extra and indeed it does seem your best fit

dodobas, did not see you pointing towards extra ... it's clear now.

but yeah, if one wants to avoid raw sql, there's still my first abomination....

dang`r`us, your ExpressionWrapper does have the advantage of being immune to sql injection, though.

danielsh, wheeee :V

Not that much injection can be done with integers...

(I suppose removing all non-digit characters from your parameter via regex or sth does the trick just as well)

My parameter is a python integer, actually.

even better

:)

danielsh: you can pass parameters to extra, which will be checked for 'sql injection' attacks

FYI, there is a pattern regarding the model fields that do not become part of the table: they are URLfield and DateTimeField

efstone, maybe you need to makemigrations and run migrate

I can assure you those fields are not broken.

I have indeed been using makemigrations and migrate. I've also examined the sqlmigrations SQL and there's no mention of those fields at all in the SQL

dodobas, thanks for pointing that out - hadn't read that far down the linked doc yet.

(trying to multitask)

I have two models for the same underlying Postgres table. Do I need to add db_index=True to a given field in both the models, or only one of them?

infinitesum: that sounds terrifying; why?

doismellburning: There are basically a bunch of fields on my model that I need to store, but that I don’t want to return to the users when rendering JSON responses. So I created a second set of ‘ReadOnly’ models with managed=False, so that way I’m not retrieving unnecessary fields or risking accidently leaking non-public information to users

doismellburning: I think I saw in the docs somewhere that if you’re going to be doing that on a one-off basis, just use deferred, but if you’re going to do it on a regular basis then you can just have alternate models that are missing some of the fields on the managed model

infinitesum: right; are you using DRF at all?

doismellburning: Yes, I am

infinitesum: consider using DRF and using different Serializers

not different models

doismellburning: Is there a good way then to not retrieve the db fields I don’t actually need, rather than just not serializing them after they’re retrieved?

infinitesum: why does that matter?

doismellburning: Really only for query speed

infinitesum: your bottleneck is data transfer?

How do I temporary hold data fetched by celery till the client asks for it?

*temporarily

doismellburning: I haven’t launched yet so we have yet to benchmark anything

: doismellburning: But db performance is what I’m most worried about… For reference this is just for the one table used to generate the news feed on a social network type site

doismellburning: I looked into it, I think I’m just going to use an abstract table so that was I still have both a managed and unmanaged table, but I don’t need to repeat all the field definitions in both places