姜戈：1.11
我正在django-pyodbc-azure用作我的 Django 后端。它正在连接到 SQL Server 2012。SQL Server 的参数限制为 2,100 个。当我尝试prefetch_related在将返回超过 2,100 个结果的查询集上使用时......
def object_search_list(request):
objects = MyModel.objects.filter(some_field='filter value').select_related('another_field').prefetch_related('a_third_field')
print(objects)
return render(request, 'objects/object_list.html', {'objects':objects})
...返回此错误：
Exception Value: ('07002', '[07002] [Microsoft][SQL Server Native Client 11.0]COUNT field incorrect or syntax error (0) (SQLExecDirectW)')
它指向 .pyodbc 使用的后端django-pyodbc-azure。查看功能时（https://github.com/michiya/django-pyodbc-azure/blob/azure-2.1/sql_server/pyodbc/features.py），没有max_query_params设置。我试图手动添加max_query_params = 2100. 这导致了同样的错误。将该值设置为 2000 和 1000 也会导致相同的错误。
如何调整django-pyodbc-azure以自动处理此 SQL Server 限制？
Django 的 Oracle 后端具有这样的功能：https ://github.com/django/django/blob/master/django/db/backends/oracle/features.py
更新：
我意识到这个max_query_params名字对于 Django 2.0 来说是新的。因此，我尝试max_limit_in_size匹配 Django 1.11。仅仅是django-pyodbc-azure不支持控制参数计数和base.py覆盖 Django 的默认值base.py吗？
更新 2：
我升级到 Django 2.1 并升级django-pyodbc-azure到匹配。然后我进行了编辑features.py以添加max_query_params = 2000为功能。另一个max_query_params出现在 Django 本地后端的地方是operations.py在这个函数中（Oracle 示例）：
def bulk_batch_size(self, fields, objs):
"""Oracle restricts the number of parameters in a query."""
if fields:
return self.connection.features.max_query_params // len(fields)
return len(objs)
django-pyodbc-azure也有这个功能，它看起来像这样：
def bulk_batch_size(self, fields, objs):
"""
Returns the maximum allowed batch size for the backend. The fields
are the fields going to be inserted in the batch, the objs contains
all the objects to be inserted.
"""
objs_len, fields_len, max_row_values = len(objs), len(fields), 1000
if (objs_len * fields_len) <= max_row_values:
size = objs_len
else:
size = max_row_values // fields_len
return size
似乎它已经处理了max_row_values设置为 1000 的批处理。但是，同样的错误仍然存在。我也尝试将1000更改max_query_params为无济于事。
这是完整的追溯：
Traceback:
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\backends\utils.py" in _execute
85. return self.cursor.execute(sql, params)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\sql_server\pyodbc\base.py" in execute
546. return self.cursor.execute(sql, params)
The above exception (('07002', '[07002] [Microsoft][SQL Server Native Client 11.0]COUNT field incorrect or syntax error (0) (SQLExecDirectW)')) was the direct cause of the following exception:
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\core\handlers\exception.py" in inner
34. response = get_response(request)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\core\handlers\base.py" in _get_response
126. response = self.process_exception_by_middleware(e, request)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\core\handlers\base.py" in _get_response
124. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\contrib\auth\decorators.py" in _wrapped_view
21. return view_func(request, *args, **kwargs)
File "C:\Users\user\djangoproject\app\views.py" in object_list
486. return render(request, 'objects/object_list.html', {'objects':objects})
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\shortcuts.py" in render
36. content = loader.render_to_string(template_name, context, request, using=using)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\loader.py" in render_to_string
62. return template.render(context, request)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\backends\django.py" in render
61. return self.template.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\template_timings_panel\panels\TemplateTimings.py" in timing_hook
139. result = func(self, *args, **kwargs)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render
171. return self._render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\test\utils.py" in instrumented_test_render
96. return self.nodelist.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render
937. bit = node.render_annotated(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render_annotated
904. return self.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\loader_tags.py" in render
150. return compiled_parent._render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\test\utils.py" in instrumented_test_render
96. return self.nodelist.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render
937. bit = node.render_annotated(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render_annotated
904. return self.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\template_timings_panel\panels\TemplateTimings.py" in timing_hook
139. result = func(self, *args, **kwargs)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\loader_tags.py" in render
62. result = block.nodelist.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render
937. bit = node.render_annotated(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render_annotated
904. return self.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\loader_tags.py" in render
188. return template.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\template_timings_panel\panels\TemplateTimings.py" in timing_hook
139. result = func(self, *args, **kwargs)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render
173. return self._render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\test\utils.py" in instrumented_test_render
96. return self.nodelist.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render
937. bit = node.render_annotated(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\base.py" in render_annotated
904. return self.render(context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\template\defaulttags.py" in render
166. len_values = len(values)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\models\query.py" in __len__
250. self._fetch_all()
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\models\query.py" in _fetch_all
1188. self._prefetch_related_objects()
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\models\query.py" in _prefetch_related_objects
723. prefetch_related_objects(self._result_cache, *self._prefetch_related_lookups)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\models\query.py" in prefetch_related_objects
1569. obj_list, additional_lookups = prefetch_one_level(obj_list, prefetcher, lookup, level)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\models\query.py" in prefetch_one_level
1699. all_related_objects = list(rel_qs)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\models\query.py" in __iter__
268. self._fetch_all()
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\models\query.py" in _fetch_all
1186. self._result_cache = list(self._iterable_class(self))
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\models\query.py" in __iter__
54. results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\models\sql\compiler.py" in execute_sql
1065. cursor.execute(sql, params)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\debug_toolbar\panels\sql\tracking.py" in execute
186. return self._record(self.cursor.execute, sql, params)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\debug_toolbar\panels\sql\tracking.py" in _record
124. return method(sql, params)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\backends\utils.py" in execute
100. return super().execute(sql, params)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\backends\utils.py" in execute
68. return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\backends\utils.py" in _execute_with_wrappers
77. return executor(sql, params, many, context)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\backends\utils.py" in _execute
85. return self.cursor.execute(sql, params)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\utils.py" in __exit__
89. raise dj_exc_value.with_traceback(traceback) from exc_value
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\django\db\backends\utils.py" in _execute
85. return self.cursor.execute(sql, params)
File "C:\Users\user\installed\anaconda\envs\django2\lib\site-packages\sql_server\pyodbc\base.py" in execute
546. return self.cursor.execute(sql, params)
Exception Type: Error at url
Exception Value: ('07002', '[07002] [Microsoft][SQL Server Native Client 11.0]COUNT field incorrect or syntax error (0) (SQLExecDirectW)')