django - 已经使用不同的查询集看到了查找
问题描述
我对学分列表进行排序ajax request
。第一次一切顺利时,我得到了排序的学分列表和update the cache
. 但是当我再次尝试排序时,我得到一个错误。
'creditpayments' 查找已经用不同的查询集看到。您可能需要调整查找的顺序。
如果缓存不更新,则不会出现错误。但我需要更新它...
楷模
class Credit(models.Model):
pass
class CreditPayment(models.Model):
credit = models.ForeignKey(Credit, on_delete=models.CASCADE, related_name='creditpayments')
rate = models.DecimalField(_('rate'), max_digits=7, decimal_places=2)
意见
class SortedCreditsList(ListView):
def get(self, *args, **kwargs):
if self.request.is_ajax():
credits = cache.get('credits')
prefetch = Prefetch('creditpayments', CreditPayment.objects.all())
credits = credits.prefetch_related(prefetch).annotate(min_rate=Min('creditpayments__rate'))
credits = credits.order_by('min_rate')
cache.set('credits', credits)
credits = credits.filter(best=False, hot=False)
template_ajax = render_to_string(
template_name='credits/includes/credits_filter_result.html',
context={
'credits': credits,
})
return JsonResponse({'success': True, 'template': template_ajax})
追溯
ValueError at /sorted_kredit/
'creditpayments' lookup was already seen with a different queryset. You may need to adjust the ordering of your lookups.
Traceback:
File "/home/m0nte-cr1st0/.virtualenvs/finbee/local/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
149. response = self.process_exception_by_middleware(e, request)
File "/home/m0nte-cr1st0/.virtualenvs/finbee/local/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
147. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/home/m0nte-cr1st0/.virtualenvs/finbee/local/lib/python2.7/site-packages/django/views/generic/base.py" in view
68. return self.dispatch(request, *args, **kwargs)
File "/home/m0nte-cr1st0/.virtualenvs/finbee/local/lib/python2.7/site-packages/django/views/generic/base.py" in dispatch
88. return handler(request, *args, **kwargs)
File "/home/m0nte-cr1st0/work_projects/startup/finbee/credits/views.py" in get
555. cache.set('credits', credits)
File "/home/m0nte-cr1st0/.virtualenvs/finbee/local/lib/python2.7/site-packages/django/core/cache/backends/locmem.py" in set
75. pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
File "/home/m0nte-cr1st0/.virtualenvs/finbee/local/lib/python2.7/site-packages/django/db/models/query.py" in __getstate__
211. self._fetch_all()
File "/home/m0nte-cr1st0/.virtualenvs/finbee/local/lib/python2.7/site-packages/django/db/models/query.py" in _fetch_all
1076. self._prefetch_related_objects()
File "/home/m0nte-cr1st0/.virtualenvs/finbee/local/lib/python2.7/site-packages/django/db/models/query.py" in _prefetch_related_objects
656. prefetch_related_objects(self._result_cache, self._prefetch_related_lookups)
File "/home/m0nte-cr1st0/.virtualenvs/finbee/local/lib/python2.7/site-packages/django/db/models/query.py" in prefetch_related_objects
1397. "You may need to adjust the ordering of your lookups." % lookup.prefetch_to)
解决方案
预取你已经预取的模型导致的错误。
当您credits
从缓存中获取值时,该对象已经预取。
if hasattr(cache, 'credits`): # Already Cached
credits = cache.get('credits')
else:
prefetch = Prefetch('creditpayments', CreditPayment.objects.all())
credits = credits.prefetch_related(prefetch).annotate(min_rate=Min('creditpayments__rate'))
credits = credits.order_by('min_rate')
cache.set('credits', credits)
我认为这段代码使您的代码正常工作。
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