使用Sphinxsearch时Django MySQL后端获取特性报错求助

Django的MySQL后端每次建立连接时会评估MySQL相关设置，而Sphinx返回的@@SQL_AUTO_IS_NULL值为空字符串，无法转换为整数，执行migrate命令时抛出如下错误：

root@2d37585a3d96:/mealplanner/trunk# python manage.py migrate
Traceback (most recent call last):
File "manage.py", line 11, in <module>
execute_from_command_line(sys.argv)
File "/py36-default/lib/python3.6/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
utility.execute()
File "/py36-default/lib/python3.6/site-packages/django/core/management/__init__.py", line 375, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/py36-default/lib/python3.6/site-packages/django/core/management/base.py", line 323, in run_from_argv
self.execute(*args, **cmd_options)
File "/py36-default/lib/python3.6/site-packages/django/core/management/base.py", line 361, in execute
self.check()
File "/py36-default/lib/python3.6/site-packages/django/core/management/base.py", line 390, in check
include_deployment_checks=include_deployment_checks,
File "/py36-default/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 64, in _run_checks
issues = run_checks(tags=[Tags.database])
File "/py36-default/lib/python3.6/site-packages/django/core/checks/registry.py", line 72, in run_checks
new_errors = check(app_configs=app_configs)
File "/py36-default/lib/python3.6/site-packages/django/core/checks/database.py", line 10, in check_database_backends
issues.extend(conn.validation.check(**kwargs))
File "/py36-default/lib/python3.6/site-packages/django/db/backends/mysql/validation.py", line 9, in check
issues.extend(self._check_sql_mode(**kwargs))
File "/py36-default/lib/python3.6/site-packages/django/db/backends/mysql/validation.py", line 13, in _check_sql_mode
with self.connection.cursor() as cursor:
File "/py36-default/lib/python3.6/site-packages/django/db/backends/base/base.py", line 256, in cursor
return self._cursor()
File "/py36-default/lib/python3.6/site-packages/django/db/backends/base/base.py", line 233, in _cursor
self.ensure_connection()
File "/py36-default/lib/python3.6/site-packages/django/db/backends/base/base.py", line 217, in ensure_connection
self.connect()
File "/py36-default/lib/python3.6/site-packages/django/db/backends/base/base.py", line 197, in connect
self.init_connection_state()
File "/py36-default/lib/python3.6/site-packages/django/db/backends/mysql/base.py", line 231, in init_connection_state
if self.features.is_sql_auto_is_null_enabled:
File "/py36-default/lib/python3.6/site-packages/django/utils/functional.py", line 80, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/py36-default/lib/python3.6/site-packages/django/db/backends/mysql/features.py", line 83, in is_sql_auto_is_null_enabled
cursor.execute('SELECT @@SQL_AUTO_IS_NULL')
File "/py36-default/lib/python3.6/site-packages/django/db/backends/utils.py", line 99, in execute
return super().execute(sql, params)
File "/py36-default/lib/python3.6/site-packages/django/db/backends/utils.py", line 67, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "/py36-default/lib/python3.6/site-packages/django/db/backends/utils.py", line 76, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/py36-default/lib/python3.6/site-packages/django/db/backends/utils.py", line 82, in _execute
return self.cursor.execute(sql)
File "/py36-default/lib/python3.6/site-packages/django/db/backends/mysql/base.py", line 71, in execute
return self.cursor.execute(query, args)
File "/py36-default/lib/python3.6/site-packages/MySQLdb/cursors.py", line 250, in execute
self.errorhandler(self, exc, value)
File "/py36-default/lib/python3.6/site-packages/MySQLdb/connections.py", line 50, in defaulterrorhandler
raise errorvalue
File "/py36-default/lib/python3.6/site-packages/MySQLdb/cursors.py", line 247, in execute
res = self._query(query)
File "/py36-default/lib/python3.6/site-packages/MySQLdb/cursors.py", line 413, in _query
self._post_get_result()
File "/py36-default/lib/python3.6/site-packages/MySQLdb/cursors.py", line 417, in _post_get_result
self._rows = self._fetch_row(0)
File "/py36-default/lib/python3.6/site-packages/MySQLdb/cursors.py", line 385, in _fetch_row
return self._result.fetch_row(size, self._fetch_type)
ValueError: invalid literal for int() with base 10: ''

在MySQL客户端连接Sphinx时执行SELECT @@SQL_AUTO_IS_NULL，返回结果为空字符串：

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 2.2.11-id64-release (95ae9a6)

Copyright (c) 2000, 2023, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> SELECT @@SQL_AUTO_IS_NULL;
+--------------------+
| @@sql_auto_is_null |
+--------------------+
|                    |
+--------------------+
1 row in set (0.00 sec)

解决方案 #

方案1：修改Sphinx配置强制返回合法值 #

在Sphinx的配置文件（通常为sphinx.conf）中，添加sql_query_pre指令，让Sphinx在每次处理查询前自动设置SQL_AUTO_IS_NULL的值：

sql_query_pre = SET SQL_AUTO_IS_NULL = 0

配置生效后，SELECT @@SQL_AUTO_IS_NULL会返回整数0，符合Django的类型要求。

方案2：自定义Django MySQL后端适配空字符串 #

如果无法修改Sphinx配置，可通过自定义数据库后端捕获转换异常：

1. 创建自定义后端文件（如custom_mysql/backends/mysql/base.py），继承原MySQL后端并重写特性类：

from django.db.backends.mysql.base import DatabaseWrapper as OriginalMySQLWrapper
from django.db.backends.mysql.features import DatabaseFeatures as OriginalMySQLFeatures

class DatabaseFeatures(OriginalMySQLFeatures):
    @property
    def is_sql_auto_is_null_enabled(self):
        try:
            return super().is_sql_auto_is_null_enabled
        except ValueError:
            # 空字符串时默认返回False（对应SQL_AUTO_IS_NULL=0）
            return False

class DatabaseWrapper(OriginalMySQLWrapper):
    features_class = DatabaseFeatures

2. 在Django的settings.py中修改数据库配置，使用自定义后端：

DATABASES = {
    'default': {
        'ENGINE': 'custom_mysql.backends.mysql',
        # 其他数据库连接配置...
    }
}

内容的提问来源于stack exchange，提问作者Vlad