所以我有一个基于1.6.5的django项目，现在我将它迁移到1.9.5。我成功地将其迁移到1.7.0然后再迁移到1.8.0。当从1.8.0到1.9.0这样做时，我不得不用collections.OrderedDict替换SortedDict。现在，当我进行python manage.py test时，我遇到了这个错误：
File "forum/models/base.py", line 134, in iterator
key_list = [v[0] for v in self.values_list(*values_list)]
File "venv/mystuff/lib/python2.7/site-packages/django/db/models/query.py", line 258, in __iter__
self._fetch_all()
File "venv/mystuff/lib/python2.7/site-packages/django/db/models/query.py", line 1074, in _fetch_all
self._result_cache = list(self.iterator())
File "forum/models/base.py", line 134, in iterator
key_list = [v[0] for v in self.values_list(*values_list)]
File "venv/mystuff/lib/python2.7/site-packages/django/db/models/query.py", line 258, in __iter__
self._fetch_all()
File "venv/mystuff/lib/python2.7/site-packages/django/db/models/query.py", line 1074, in _fetch_all
self._result_cache = list(self.iterator())
File "forum/models/base.py", line 134, in iterator
key_list = [v[0] for v in self.values_list(*values_list)]
File "venv/mystuff/lib/python2.7/site-packages/django/db/models/query.py", line 725, in values_list
clone = self._values(*fields)
File "venv/mystuff/lib/python2.7/site-packages/django/db/models/query.py", line 671, in _values
clone = self._clone()
File "venv/mystuff/lib/python2.7/site-packages/django/db/models/query.py", line 1059, in _clone
query = self.query.clone()
File "venv/mystuff/lib/python2.7/site-packages/django/db/models/sql/query.py", line 298, in clone
obj._annotations = self._annotations.copy() if self._annotations is not None else None
File "/opt/python/python-2.7/lib64/python2.7/collections.py", line 194, in copy
return self.__class__(self)
File "/opt/python/python-2.7/lib64/python2.7/collections.py", line 57, in __init__
self.__update(*args, **kwds)
File "venv/mystuff/lib64/python2.7/abc.py", line 151, in __subclasscheck__
if subclass in cls._abc_cache:
File "venv/mystuff/lib64/python2.7/_weakrefset.py", line 72, in __contains__
wr = ref(item)
RuntimeError: maximum recursion depth exceeded
其他类似问题的解决方案要求将python升级到2.7.5，但我已经在2.7.11上运行了它。
编辑： 论坛/模型/ base.py
def iterator(self):
cache_key = self.model._generate_cache_key("QUERY:%s" % self._get_query_hash())
on_cache_query_attr = self.model.value_to_list_on_cache_query()
to_return = None
to_cache = {}
with_aggregates = len(self.query.aggregates) > 0
key_list = self._fetch_from_query_cache(cache_key)
if key_list is None:
if not with_aggregates:
values_list = [on_cache_query_attr]
if len(self.query.extra):
values_list += self.query.extra.keys()
key_list = [v[0] for v in self.values_list(*values_list)] #Line 134
to_cache[cache_key] = (datetime.datetime.now(), key_list)
else:
to_return = list(super(CachedQuerySet, self).iterator())
to_cache[cache_key] = (datetime.datetime.now(), [
(row.__dict__[on_cache_query_attr], dict([(k, row.__dict__[k]) for k in self.query.aggregates.keys()]))
for row in to_return])
elif with_aggregates:
tmp = key_list
key_list = [k[0] for k in tmp]
with_aggregates = [k[1] for k in tmp]
del tmp
if (not to_return) and key_list:
row_keys = [self.model.infer_cache_key({on_cache_query_attr: attr}) for attr in key_list]
cached = cache.get_many(row_keys)
to_return = [
(ck in cached) and self.obj_from_datadict(cached[ck]) or ToFetch(force_unicode(key_list[i])) for i, ck in enumerate(row_keys)
]
if len(cached) != len(row_keys):
to_fetch = [unicode(tr) for tr in to_return if isinstance(tr, ToFetch)]
fetched = dict([(force_unicode(r.__dict__[on_cache_query_attr]), r) for r in
models.query.QuerySet(self.model).filter(**{"%s__in" % on_cache_query_attr: to_fetch})])
to_return = [(isinstance(tr, ToFetch) and fetched[unicode(tr)] or tr) for tr in to_return]
to_cache.update(dict([(self.model.infer_cache_key({on_cache_query_attr: attr}), r._as_dict()) for attr, r in fetched.items()]))
if with_aggregates:
for i, r in enumerate(to_return):
r.__dict__.update(with_aggregates[i])
if len(to_cache):
cache.set_many(to_cache, 60 * 60)
if to_return:
for row in to_return:
if hasattr(row, 'leaf'):
row = row.leaf
row.reset_original_state()
yield row
django的/分贝/模型/ query.py：
def _fetch_all(self):
if self._result_cache is None:
self._result_cache = list(self.iterator()) #Line 1074
if self._prefetch_related_lookups and not self._prefetch_done:
self._prefetch_related_objects()
django的/分贝/模型/ query.py
def __iter__(self):
"""
The queryset iterator protocol uses three nested iterators in the
default case:
1. sql.compiler:execute_sql()
- Returns 100 rows at time (constants.GET_ITERATOR_CHUNK_SIZE)
using cursor.fetchmany(). This part is responsible for
doing some column masking, and returning the rows in chunks.
2. sql/compiler.results_iter()
- Returns one row at time. At this point the rows are still just
tuples. In some cases the return values are converted to
Python values at this location.
3. self.iterator()
- Responsible for turning the rows into model objects.
"""
self._fetch_all() #Line 258
return iter(self._result_cache)
更新： 我的Django Log显示了这个：
/forum/settings/base.py TIME: 2017-06-27 06:49:53,410 MSG: base.py:value:65 Error retrieving setting from database (FORM_EMPTY_QUESTION_BODY): maximum recursion depth exceeded in cmp
/forum/settings/base.py TIME: 2017-06-27 06:49:53,444 MSG: base.py:value:65 Error retrieving setting from database (FORM_MIN_NUMBER_OF_TAGS): maximum recursion depth exceeded
答案 0 :(得分：3)
所以你从迭代器中调用values_list()，迭代器克隆QuerySet，它迭代QuerySet，它调用你的迭代器，克隆了Queryset ......
API在this commit中更改了。它应该为您提供足够的信息来重新实现您的Queryset。
另一方面，看起来Django本身已经实现了查询缓存，所以在重构之前你可能会看看你的CachedQuerySet已经过时了。