a) Maybe its an option to put the foreign key to the other model? This way
you dont need to make a join to find out if there is a relation.
b) Save the existing ralation status to model A
c) cache the A.objects.filter(bs__isnull=False) query
But apart from that i fear you cannot do much more, since this is just a DB
and not a Django ORM question.
Am Freitag, 2. Februar 2018 14:47:45 UTC+1 schrieb Web Architect:
>
> Hi,
>
> I am trying to optimise Django queries on my ecommerce website. One of the
> fundamental query is where I have no clue how to make efficient. It could
> be trivial and probably been known long time back. But I am new to Django
> and would appreciate any help. This is primarily for one to many or many to
> many relations.
>
> Following is an example scenario:
> (Please pardon my syntax as I want to put across the concept and not the
> exact django code unless it's really needed):
>
> Model A:
>
> class A(models.Model):
> # Fields of model A
>
> Model B (which is related to A with foreign key):
>
> class B(models.Model):
> a = models.ForeignKey('A', related_name='bs')
>
> Now I would like to find out all As for which there is atleast one b. The
> only way I know is as follows:
>
> A.objects.filter(bs__isnull=False)
>
> But the above isn't an optimal way as with large of records in A and B,
> the above takes lot of time. It gets more inefficient if it's a many to
> many relationship.
>
> Could anyone please let me know the most efficient way to use django
> queryset for the above scenario?
>
> Thanks.
>
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