Hi, I've been thinking what is the best way to address #28333 <https://code.djangoproject.com/ticket/28333> - it is desirable to be able to filter by Window expression in ORM. But that requires using subqueries in sql. The ticket itself proposes doing so implicitly and keeping the usual filter interface:
qs.annotate(row=Window(expression=RowNumber())).filter(row__gt=1) But that raises the question - how the expression below should be interpreted? qs.annotate(row=Window(expression=RowNumber())).filter(row__gt=1, id__gt=1) Should id__gt go to the inner or the outer query? More generally, is it OK for a queryset to be dependent on the order of .filter() calls? I feel this would be quite surprising. So it's probably better to make this operation more explicit. It was suggested by Anssi Kääriäinen in #24462 <https://code.djangoproject.com/ticket/24462> to add .subquery() method to querysets. This seems like yet another use case! But I tried to implement it, and almost immediately found an ambiguous case: qs.values('id').subquery().filter(other_field=...) We can't just apply filter to the outer query - it doesn't have other_field anymore due to values() call. What to do? Reject such an attempt? Apply values() only to the outer query, not the inner one? Apply filter() to the inner one (this is probably the most surprising...)? Something else? No doubt there are many more tricky questions about semantics of such a method. But I'd like to start this discussion somewhere. :) So, a few questions: 1. Do you agree that adding QuerySet.subquery is worthwhile? 2. Do you agree it is the best way to solve #28333 <https://code.djangoproject.com/ticket/28333>? 3. How should it behave, in the specific case above or maybe more generally? Thanks. -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-developers+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/CAO0xAt4kfZEKnDA38kx%3DujgMV3vrRpoptFAJLu_a1XtmMOUSDw%40mail.gmail.com.
