Question

When I do something like

I. objects = Model.objects.all()

and then

II. objects.filter(field_1=some_condition)

I hit db every time when on the step 2 with various conditions. Is there any way to get all data in first action and then just take care of the result?

Answer 1

You actually don’t hit the db until you evaluate the qs, queries are lazy.

Read more here.

edit:

After re-reading your question it becomes apparent you were asking how to prevent db hits when filtering for different conditions.

qs = SomeModel.objects.all()

qs1 = qs.filter(some_field='some_value')
qs2 = qs.filter(some_field='some_other_value')

Usually you would want the database to do the filtering for you.

You could force an evaluation of the qs by converting it to a list. This would prevent further db hits, however it would likely be worse than having your db return you results.

qs_l = list(qs)
qs1_l = [element for element in qs_l if element.some_field='some_value']
qs2_l = [element for element in qs_l if element.some_field='some_other_value']