Personally, the snippet suggested in the ticket is sufficient for my needs 
(although I'm saddened by having to duplicate the setattr logic).
However, I filed the ticket after Googling "Django conditional 
update_or_create" and finding no appropriate solution. You might be right 
about the use case being niche, however others have ran into this too, with 
the proposed solutions being less-than-ideal.
(I won't link anything here, but searching stackoverflow for "Django 
conditional update_or_create" should lead you to the same question/answers 
I came across).

Perhaps the "solution" here isn't additional code, but rather a section in 
documentation that suggests a solution? It's extremely unfortunate that 
this is easy to get wrong in so many ways, but also isn't appropriate to 
add directly to Django.



On Friday, December 28, 2018 at 12:38:04 PM UTC-6, Adam Johnson wrote:
>
> I think the use case is probably quite niche, and I'd like to know some 
> more concrete details than the current comment on the ticket "(E.g. only 
> update if the value of a DateTimeField is less than some value)". It may be 
> there's a way to achieve the same application-level outcome using a 
> different design. If it is necessary, there are also some analogous use 
> cases, like passing a 'create' condition predicate or passing conditions to 
> get_or_create, that it seems it would make sense to implement at the same 
> time but would complicate Django and the scope of the change further.
>
> Also I agree with Simon that passing around predicate callables doesn't 
> feel very Django-ey or pythonic.
>
> On Fri, 28 Dec 2018 at 16:31, charettes <chare...@gmail.com <javascript:>> 
> wrote:
>
>> Thanks for taking the time to post here Joshua!
>>
>> The main reason why I asked to gather feedback from this list is that I'm 
>> not convinced
>> that the benefits outweighs the additional complexity this will add to 
>> the already quite
>> loaded update_or_create() signature handling and how the fact a callable 
>> predicate
>> is not something that is used anywhere else in Django AFAIK.
>>
>> The fact this can be achieved with the same number of queries by doing a
>> save(update_fields) from the return value of a previous get_or_create 
>> with a
>> bit of boilerplate[0] pushes me to a -1 because I don't think it's a 
>> common enough
>> pattern to warrant the addition of a specialized option.
>>
>> Cheers,
>> Simon
>>
>> [0] https://code.djangoproject.com/ticket/30053#comment:13
>>
>> Le vendredi 28 décembre 2018 11:15:33 UTC-5, Joshua Cannon a écrit :
>>>
>>> Howdy folks!
>>>
>>> At the suggestion of Simon Charette, I'd like to get feedback on how the 
>>> community feels about the feature request #30053 
>>> <https://code.djangoproject.com/ticket/30053>.
>>> The gist of the problem is that sometimes the "update" part of 
>>> "update_or_create" should be conditional. The proposed solution adds a 
>>> backwards-compatible "update_condition" parameter to "update_or_create" 
>>> which should be a unary callable that takes in the retrieved table instance 
>>> and returns a boolean of whether the update should be performed.
>>>
>>> Nasir Hussain has already started work on a possible solution on PR 
>>> 10800 <https://github.com/django/django/pull/10800>.
>>>
>>> I'd love to hear other people's thoughts.
>>>
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>
> -- 
> Adam
>

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