Django 2.1.5，带有MySQL后端。
我的django应用有效。此问题与测试有关。在django代码中添加了查询打印，但此行失败：
ALTER TABLE `documents`
ADD CONSTRAINT`documents_assessment_perspecti_2890f0af_fk_assess_pe`
FOREIGN KEY (`assessment_perspective`) REFERENCES `assess_perspectives` (`id`)
我通过命令行工具进入MySQL，发现在运行上述外键命令时，在test_db中尚未创建'assess_perspectives'表。我想知道，Django在测试运行期间如何决定表创建的顺序？这是Django错误，还是我使用的方式不正确？有什么方法可以强制在测试中首先创建“ assessment_perspective”表？
运行测试
python manage.py test document --settings=myapp.settings.local
我的简化模型
class AssessPerspective(models.Model):
_id = models.AutoField(db_column='id', primary_key=True)
name = models.CharField(db_column='name', max_length=255, blank=True, null=True)
class Documents(models.Model):
assessment_perspective = models.ForeignKey(AssessPerspective, models.DO_NOTHING, db_column='assessment_perspective', blank=True, null=True)
......
例外
Traceback (most recent call last):
File "/Users/xxx/myapp/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/backends/mysql/base.py", line 71, in execute
return self.cursor.execute(query, args)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/MySQLdb/cursors.py", line 198, in execute
res = self._query(query)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/MySQLdb/cursors.py", line 306, in _query
db.query(q)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/MySQLdb/connections.py", line 217, in query
_mysql.connection.query(self, query)
MySQLdb._exceptions.IntegrityError: (1215, 'Cannot add foreign key constraint')
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 15, in <module>
execute_from_command_line(sys.argv)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
utility.execute()
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/__init__.py", line 375, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/commands/test.py", line 26, in run_from_argv
super().run_from_argv(argv)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/base.py", line 316, in run_from_argv
self.execute(*args, **cmd_options)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/base.py", line 353, in execute
output = self.handle(*args, **options)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/commands/test.py", line 56, in handle
failures = test_runner.run_tests(test_labels)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/test/runner.py", line 604, in run_tests
old_config = self.setup_databases()
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/test/runner.py", line 551, in setup_databases
self.parallel, **kwargs
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/test/utils.py", line 174, in setup_databases
serialize=connection.settings_dict.get('TEST', {}).get('SERIALIZE', True),
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/backends/base/creation.py", line 68, in create_test_db
run_syncdb=True,
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/__init__.py", line 148, in call_command
return command.execute(*args, **defaults)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/base.py", line 353, in execute
output = self.handle(*args, **options)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/base.py", line 83, in wrapped
res = handle_func(*args, **kwargs)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/core/management/commands/migrate.py", line 203, in handle
fake_initial=fake_initial,
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/migrations/executor.py", line 117, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/migrations/executor.py", line 147, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
state = migration.apply(state, schema_editor)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 106, in __exit__
self.execute(sql)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 133, in execute
cursor.execute(sql, params)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 68, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/utils.py", line 89, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/django/db/backends/mysql/base.py", line 71, in execute
return self.cursor.execute(query, args)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/MySQLdb/cursors.py", line 198, in execute
res = self._query(query)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/MySQLdb/cursors.py", line 306, in _query
db.query(q)
File "/Users/xxx/myapp/see/env/lib/python3.7/site-packages/MySQLdb/connections.py", line 217, in query
_mysql.connection.query(self, query)
django.db.utils.IntegrityError: (1215, 'Cannot add foreign key constraint')
更新：找到了根本原因
plan = executor.migration_plan(targets)返回当前
/ myapp / migrations / xxx文件，而不是从模型进行全新的迁移。class Meta: managed = False。一开始我是手动管理它们，但是在初始设置和一切正常后，我应该将它们更改为managed = True。managed: True，创建空数据库，makemigration，迁移（为不可为空的列填写一些默认值。完成） 。固定。