在get_context_data中更改queryset后，分页不起作用

Question

Pagination works ok until I add reverse arg to QS for ordering queryset in reverse mode. After it pagination is broke. I can use get() function and paginate it there, but I think that for this issue should be better solution. Thanks

model.py:

class Log(models.Model):
    user = models.ForeignKey('auth.User')
    comment = models.CharField()
    date_add = models.DateTimeField()
    class Meta:
        ordering = ['-date_add']

view.py:

class LogView(ListView):
    model = UserLog
    template_name = 'log.html'
    context_object_name = 'log_list'
    paginate_by = 13

    def get_queryset(self):
        return Log.objects.filter(user=self.request.user).all()

    def get_context_data(self, *, object_list=None, **kwargs):
        context = super(LogView, self).get_context_data(**kwargs)
        if 'reverse' in self.request.GET:
            context['log_list'] = Log.objects.filter(user=self.request.user).all().order_by('date_add')
        return context

Answer 1

Move the code that runs the queryset to get_queryset , so that it runs before the queryset is paginated.

def get_queryset(self):
    queryset = Log.objects.filter(user=self.request.user).all()
    if 'reverse' in self.request.GET:
        queryset = queryset.order_by('date_add')
    return queryset

Answer 2

The pagination is called in the get_context_data of the MultipleObjectMixin [GitHub] :

 def get_context_data(self, *, object_list=None, **kwargs): """Get the context for this view.""" queryset = object_list if object_list is not None else self.object_list page_size = self.get_paginate_by(queryset) context_object_name = self.get_context_object_name(queryset) if page_size: paginator, page, queryset, is_paginated = self.paginate_queryset(queryset, page_size) context = { 'paginator': paginator, 'page_obj': page, 'is_paginated': is_paginated, 'object_list': queryset } else: context = { 'paginator': None, 'page_obj': None, 'is_paginated': False, 'object_list': queryset } if context_object_name is not None: context[context_object_name] = queryset context.update(kwargs) return super().get_context_data(**context) 

By overriding the element of the dictionary, you thus bypass this pagination.

I think it is however better in this use-case to transfer the logic to the get_queryset method, in that case, you even do not have to override the get_context_data :

class LogView(ListView):
    model = UserLog
    template_name = 'log.html'
    context_object_name = 'log_list'
    paginate_by = 13

    def get_queryset(self):
        if :
            return Log.objects.filter(user=self.request.user).all().order_by('date_add')
        else:
            return Log.objects.filter(user=self.request.user).all()

Note that the above has two potential problems:

1. you do not order the queryset in case 'reverse' is not in self.request.GET , which means that - unless you order in the model - there is no order, and hence pagination might go wrong over multiple pages;
2. since pagiantion uses already a page key in request.GET , this can result in some trouble in the links that change the GET parameter, since if you specify an url with ?page=3 , the reverse key will get dropped.