If you just want one object that matches your filters during debugging, without
overhead, why don’t you use .last() instead?
> On 14 Apr 2019, at 7:14 am, Tom Forbes <t...@tomforb.es> wrote:
>
> I don’t think we should add a method like this for a few reasons. Firstly
> without an order by in SQL the order of rows is undefined, in practice myql
> orders rows but Postgres returns a different order per transaction. This will
> be confusing to users who don’t understand this and come to implicitly rely
> on first() being stable.
>
> Secondly if you are filtering on an indexed column the overhead will be next
> to none. Is this not the case?
>
> And lastly, changing this would be major backwards incompatible change.
>
> Tom
>
>> On 13 Apr 2019, at 21:58, alTus <mortas...@gmail.com> wrote:
>>
>> I've posted the source code if `first`. You can see there that if qs is not
>> ordered then ordering by pk is added.
>> It's the main point of this issue btw.
>>
>> суббота, 13 апреля 2019 г., 22:53:52 UTC+3 пользователь Florian Apolloner
>> написал:
>>>
>>> qs.order_by().first() should do what you want and is not worth adding .one()
>>>
>>> Cheers,
>>> Florian
>>>
>>>> On Saturday, April 13, 2019 at 5:48:29 PM UTC+2, alTus wrote:
>>>> Hello.
>>>>
>>>> Please consider if that proposal can be useful not only for me :)
>>>>
>>>> `QuerySet.first` is quite useful shortcut but its drawback is that it
>>>> involves ordering so some DB queries become expensive.
>>>> But quite often (and very often while debugging) there's a need just to
>>>> get one object that satisfy some filters.
>>>>
>>>> Current `first` implementation to compare with:
>>>>
>>>> def first(self):
>>>> """Return the first object of a query or None if no match is
>>>> found."""
>>>> for obj in (self if self.ordered else self.order_by('pk'))[:1]:
>>>> return obj
>>>>
>>>> Proposal (as an example of implementation):
>>>>
>>>> def one(self):
>>>> """Return one random object of a query or None if no match is
>>>> found."""
>>>> for obj in self.order_by()[:1]:
>>>> return obj
>>>>
>>>> That would be short, simple and wouldn't require any imports in client
>>>> code.
>>>>
>>>> Thank you.
>>>>
>>
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