How to get all objects linked via ForignKey from QuerySet of linked object model?

Question

Django

There was a problem with the speed of executing queries to database tables due to the strong nesting of objects.
Models:

class Model1(models.Model):
    field = models.CharField(max_lenght=100)

class Model2(models.Model):
    field = models.ForignKey(Model1, 'model_1', related_name='model_1', on_delete=models.CASCADE)

class Model3(models.Model):
    field = models.ForignKey(Model2, 'model_2', related_name='model_2', on_delete=models.CASCADE)

How can I get a QuerySet of Model3 objects linked through Model2 objects to Model1 objects. However, without using something like this:

Model3.objects.filter(model_2__model_1_id__in=Model1.objects.filter(.....).values('id'))

The given request fulfills terribly long, even on the minimum data set. In the official documentation, I found the select_related and prefetch_related methods, but I didn’t quite understand how they work and I’m not sure if I even need them. Please tell me the correct solution to this problem, I'm sure it's easy, just not obvious. Thank you!

Answer 1

it should not be long, maybe something else slows down here, put django-debug-toolbar and see what request and its plan