django, order matters when applying multiple query filters?

Question

Does order of filter matter when you query in django?

MyModel.objects.filter(exp1).filter(exp2)

vs

MyModel.objects.filter(exp2).filter(exp1)

Are they same?

Answer 1

If you are just doing two simple filter operations, then you're correct that order doesn't matter, but be careful. There are examples of when the order of your queryset methods do matter:

• https://docs.djangoproject.com/en/dev/topics/db/aggregation/#order-of-annotate-and-filter-clauses
• https://docs.djangoproject.com/en/dev/ref/models/querysets/#distinct

Rather than thinking of filter as being fundamentally commutative, you're probably safer thinking of each queryset methods as being generally iterative upon the whatever preceded them. Multiple filters are not always simple SQL AND's. Take this for example (although it's still commutative in this case).