Hello,
> On 17 Aug 2017, at 14:48, Luke Plant <[email protected]> wrote:
>
> On 16/08/17 23:17, Aymeric Augustin wrote:
>> It should kick in only when no select_related or prefetch_related is in
>> effect, to avoid interfering with pre-existing optimizations. It's still
>> easy to construct an example where it would degrade performance but I don't
>> think such situations will be common in practice.
>
> I think Ansii's example is a non-contrived and potentially very common one
> where we will make things worse if this is default behaviour, especially for
> the non-expert programmer this behaviour is supposed to help:
>
>
> if qs:
> qs[0].do_something()
>
> (where do_something() access relations, or multiple relations). We will end
> up with *multiple* large unnecessary queries instead of just one. The
> difference is that the first one is easy to explain, the remainder are much
> harder, and will contribute even more to the "Django is slow/ORMs are bad"
> feeling.
I wasn't convinced by this example because it's already sub-optimal currently.
`if qs` will fetch the whole queryset just to check if it has at least one
element.
Assuming there's 1000 elements in qs, if you don't care about a 1000x
inefficiency, I don't expect you to care much about two or three 1000x
inefficiencies...
--
Aymeric.
--
You received this message because you are subscribed to the Google Groups
"Django developers (Contributions to Django itself)" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/django-developers.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-developers/E99B1838-FBE9-4E0F-91EC-8A5DD78B8106%40polytechnique.org.
For more options, visit https://groups.google.com/d/optout.
