Django：如何计算查询集并返回切片而又不会两次击中数据库？

Question

I have this part of the code in my API which recently has become a somewhat bottleneck:

total = results.count()
if request.GET.has_key('offset'):
    offset = int(request.GET.get('offset').strip())
    results = results.order_by('name')[100*offset:100*(offset+1)]
people = list(results)

Note that results is the queryset of all the people and offset is a param used for pagination.

Here I can see, when I print connection.queries , that my database getting hit twice by .count() and list(results) . The reason why .count() has to be at the top because I need to the length of all the people (Not 100.) Is there a way to get around this?

Answer 1

Maybe something like this?:

allpeople = list(results.order_by('name'))
total = len(allpeople)
if request.GET.has_key('offset'):
    offset = int(request.GET.get('offset').strip())
    results = allpeople[100*offset:100*(offset+1)]
people = results

Keep in mind that with people = results is going to fail if if request.GET....: doesn't fire.