Re: Adding custom join support to Django

[Alexandr Artemyev]

I tried to describe my case with custom joins in django issue tracker.
I hope that I described it quite clearly. And that was helpful.
I would especially like to note that 
https://stackoverflow.com/questions/22902263/django-orm-joining-subquery/42816689#42816689
 
this solution completely suited me.

среда, 28 марта 2018 г., 10:54:06 UTC+3 пользователь Josh Smeaton написал:
>
> Someone has again brought up the lack of custom join support in django - 
> specifically LEFT OUTER joins: https://code.djangoproject.com/ticket/29262
>
> I figure it's probably something that we'd like the ORM to support but I 
> don't think we've ever really landed on a design that's palatable. I'd like 
> to try and get a rough consensus for a design and flesh out any likely 
> issues. We can then either provide a ready to go syntax that someone could 
> implement, or I could put together a DEP. At a minimum, we can point future 
> askers towards a design and "PR Welcome" them. Best case someone (possibly 
> myself) runs with the design and provides an implementation.
>
> What I'm interested in seeing are specific use cases for customising joins 
> as that will drive any kind of design.
>
> I've been playing around with some syntaxes, and this is the kind of thing 
> I'm currently leaning toward:
>
> qs = Book.objects.annotate(
> my_reviews=joins.Left(
> Review.objects.filter(user=u1),
> book=OuterRef('pk')
> )
> )
>
> This supports customising both the join type, and the join conditions (ON 
> book.id = review.book_id). One concern with this design is that now the 
> result set contains multivalues - where a book might be repeated if the 
> number of reviews that match the filter is greater than 1. We could ask the 
> user to specify whether the result is potentially multi-valued and convert 
> the result into a list, but that would require ordering and comparing the 
> current row to the previous row to check if it's a multivalue. These are 
> the kind of issues I want to flesh out, and that's only going to be 
> possible given a sufficient corpus of examples.
>
> So I'll kick off with an example that seems to be rather common:
>
> *- Add filtered results from a reverse relation / m2m relation to the 
> result set without eliminating results using a LEFT JOIN.*
>

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Re: New to Open Source Contribution Need Help With Setting Up Environment For Channels to Reproduce Issues After Cloning From Git

[Adam Johnson]

Hi Suvodeep,

Did you see this documentation page?
https://channels.readthedocs.io/en/latest/contributing.html

If you use the command:

pip install -e .

You can install your cloned channels copy in a virtual environment and use
that as normal in a channels app.

Afraid I haven't worked on it myself but the instructions seem pretty
complete. I don't think there are many people working on Channels itself
right now though.

Thanks,

Adam

On Tue, 5 Nov 2019 at 05:49, Suvodeep Dubey  wrote:

> I have cloned channels repo in my local. I was going through the bugs but
> was unable to set-up the environment to reproduce the bugs.
>
> I have the following understanding:
>
> 1. Rather than `pip install channels` clone the channels from git
> 2. Execute the channels parallel to your application and make them talk
> and see the errors in application and logs in channels.
>
> I am unable to build and run the channels and configure it with a dummy
> Django app to reproduce the bugs.
>
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> 
> .
>


-- 
Adam

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