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@eltongo
Created May 11, 2017 16:41
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A subscriptable RawQuerySet replacement in Django (tested in Django 1.11 on Python 3)
class PaginatedRawQuerySet(RawQuerySet):
def __init__(self, raw_query, **kwargs):
super(PaginatedRawQuerySet, self).__init__(raw_query, **kwargs)
self.original_raw_query = raw_query
self._result_cache = None
def __getitem__(self, k):
"""
Retrieves an item or slice from the set of results.
"""
if not isinstance(k, (slice, int,)):
raise TypeError
assert ((not isinstance(k, slice) and (k >= 0)) or
(isinstance(k, slice) and (k.start is None or k.start >= 0) and
(k.stop is None or k.stop >= 0))), \
"Negative indexing is not supported."
if self._result_cache is not None:
return self._result_cache[k]
if isinstance(k, slice):
qs = self._clone()
if k.start is not None:
start = int(k.start)
else:
start = None
if k.stop is not None:
stop = int(k.stop)
else:
stop = None
qs.set_limits(start, stop)
return qs
qs = self._clone()
qs.set_limits(k, k + 1)
return list(qs)[0]
def __iter__(self):
self._fetch_all()
return iter(self._result_cache)
def count(self):
if self._result_cache is not None:
return len(self._result_cache)
return self.model.objects.count()
def set_limits(self, start, stop):
limit_offset = ''
new_params = tuple()
if start is None:
start = 0
elif start > 0:
new_params += (start,)
limit_offset = ' OFFSET %s'
if stop is not None:
new_params = (stop - start,) + new_params
limit_offset = 'LIMIT %s' + limit_offset
self.params = self.params + new_params
self.raw_query = self.original_raw_query + limit_offset
self.query = sql.RawQuery(sql=self.raw_query, using=self.db, params=self.params)
def _fetch_all(self):
if self._result_cache is None:
self._result_cache = list(super().__iter__())
def __repr__(self):
return '<%s: %s>' % (self.__class__.__name__, self.model.__name__)
def __len__(self):
self._fetch_all()
return len(self._result_cache)
def _clone(self):
clone = self.__class__(raw_query=self.raw_query, model=self.model, using=self._db, hints=self._hints,
query=self.query, params=self.params, translations=self.translations)
return clone
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