I have a utility function in my program for searching for entities. It takes a max_count parameter. It returns a QuerySet.
I would like this function to limit the max number of entries. The standard way would be to take a slice out of my QuerySet:
return results[:max_count]
My problem is that the views which utilize this function sort in various ways by using .order_by(). This causes exceptions as re-ordering is not allowed after taking a slice.
Is it possible to force a "LIMIT 1000" into my SQL query without taking a slice?
Do results[:max_count] in a view, after .order_by(). Don't be afraid of requesting too much from DB, query won't be evaluated until the slice (and even after it either).
You could subclass QuerySet to achieve this, by simply ignore every slice and do [:max_count] at last in __getitem__, but I don't think it worths with the complex and side-effects.
If you are worrying about memory consumption by large queryset, follow http://www.mellowmorning.com/2010/03/03/django-query-set-iterator-for-really-large-querysets/
For normal usage, please just follow DrTyrsa's suggestion. You could write shortcuts to shorten the order_by and afterwards slice in code to simplify your code.
