Django :1.11
我正在使用 django-pyodbc-azure 作为我的 Django 后端。它正在连接到 SQL Server 2012。SQL Server 的参数限制为 2,100 个。当我尝试在将返回超过 2,100 个结果的查询集上使用 prefetch_related 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 django-pyodbc-azure 使用的 pyodbc 后端。查看功能 ( https://github.com/michiya/django-pyodbc-azure/blob/azure-2.1/sql_server/pyodbc/features.py ) 时，没有设置 max_query_params。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？
适用于 Django 的 Oracle 后端具有如下功能:https://github.com/django/django/blob/master/django/db/backends/oracle/features.py
更新:
我意识到 max_query_params 名称是 Django 2.0 的新名称。因此，我尝试了 max_limit_in_size 来匹配 Django 1.11。仅仅是 django-pyodbc-azure 不支持控制参数计数并且 base.py 覆盖了 Django 的默认 base.py 吗？
更新 2:
我升级到Django 2.1，升级了django-pyodbc-azure来匹配。然后，我编辑了 features.py 以添加 max_query_params = 2000 作为功能。 max_query_params 出现在 Django 原生后端的另一个地方是 operations.py 在此函数中(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
它似乎已经处理了将 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 更改为 max_query_params 无济于事。
这是完整的回溯:
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)')
请您参考如下方法:
它看起来不像是被添加到django-pyodbc-azure:
https://github.com/michiya/django-pyodbc-azure/blob/azure-2.1/sql_server/pyodbc/features.py#L4
我已将它添加到我的 fork 中:
https://github.com/FlipperPA/django-pyodbc-azure/blob/azure-2.1/sql_server/pyodbc/features.py#L33
你能给它一个测试吗？你需要升级到 Django 2.1，然后你应该能够 pip install git+https://github.com/FlipperPA/django-pyodbc-azure.git@azure-2.1 到看看它是否像添加该设置一样简单。粗略地浏览一下 Django 的源代码，它看起来可能就是全部了。如果可行，我会向 Michaya 发出拉取请求。
