Re: Optimal query for related names in onetomany or manytomany using Django Queryset

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.

--
You received this message because you are subscribed to the Google Groups "Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscribe@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at https://groups.google.com/group/django-users.
To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/d5fb0d86-aff8-4c97-a6d7-1d04ddf3d466%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.