跨多个模型定义关系 - Django

Posted 2023-02-24

【中文标题】跨多个模型定义关系 - Django

【英文标题】：Defining relationships across Multiple Models - Django

【发布时间】：2015-07-31 18:09:31

【问题描述】：

我在三个Django模型之间有如下关系：

  class TestCase(models.Model):
       '''
       Define the testcase model. A testcase is a python Class
       which contains a set of tests
       '''
       name = models.BinaryField(blank=False)
       filename = models.BinaryField(blank=True)
       run_flag = models.IntegerField(default=0)
       run_as_root = models.BooleanField(default=0)
       num_tests = models.IntegerField(default=0)
       testsuite = models.ForeignKey(TestSuite)

       def __str__(self):
           return self.name

请忽略TestSuite：这对这个问题并不重要。每个TestCase 都是你想象的：一个TestCase（类）。所以每次执行TestCase 时都会有TestExecution 和Result：

  class Result(models.Model):
       '''
       Define the result of a testcase. It may be 'PASS', 'FAIL',
       'SKIPPED' or 'ABORTED'
       '''
       FAIL = 0
       PASS = 1
       ABORTED = 2
       SKIPPED = 3

       Status = (
           (PASS, 'PASS'),
           (FAIL, 'FAIL'),
           (SKIPPED, 'SKIPPED'),
           (ABORTED, 'ABORTED'),
       )

       status = models.IntegerField(choices=Status, default=FAIL)

       testcase = models.ForeignKey(TestCase)


   class TestExecution(models.Model):

       name = models.BinaryField(blank=False)
       num_testsuites = models.IntegerField(default=0)
       time = models.FloatField()
       date = models.DateTimeField(default=django.utils.timezone.now)

      result = models.OneToOneField(Result)

      def __str__(self):
          return self.name + " : " + self.date + " : " + self.time

可以说是TestCasehasManyResult，但Result和TestExecution的关系是OneToOne。我的模型架构有一些问题。我知道一个简单的解决方案是merge 表Result 和TestExecution：

    python manage.py migrate
Operations to perform:
  Synchronize unmigrated apps: staticfiles, messages
  Apply all migrations: admin, autotester, contenttypes, auth, sessions
Synchronizing apps without migrations:
  Creating tables...
    Running deferred SQL...
  Installing custom SQL...
Running migrations:
  Rendering model states... DONE
  Applying autotester.0005_auto_20150519_1831...Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 330, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 390, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 441, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 221, in handle
    executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 110, in migrate
    self.apply_migration(states[migration], migration, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 147, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py", line 115, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/fields.py", line 62, in database_forwards
    field,
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/mysql/schema.py", line 43, in add_field
    super(DatabaseSchemaEditor, self).add_field(model, field)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/schema.py", line 403, in add_field
    self.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/schema.py", line 111, in execute
    cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 97, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/mysql/base.py", line 124, in execute
    return self.cursor.execute(query, args)
  File "/usr/local/lib/python2.7/dist-packages/MySQLdb/cursors.py", line 205, in execute
    self.errorhandler(self, exc, value)
  File "/usr/local/lib/python2.7/dist-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue
django.db.utils.IntegrityError: (1062, "Duplicate entry '0' for key 'result_id'")

关于模型架构的最合适的处理方式是什么？

根据要求添加autotester/migrations/0005_auto_20150519_1831.py：

# -- 编码：utf-8 -- 从未来导入 unicode_literals

从 django.db 导入模型，迁移

类迁移（migrations.Migration）：

    dependencies = [
       ('autotester', '0004_auto_20150519_1744'),
   ]

   operations = [
       migrations.RemoveField(
           model_name='testexecution',
           name='framework',
       ),
       migrations.AddField(
           model_name='testexecution',
           name='result',
           field=models.OneToOneField(default=None, to='autotester.Result'),
           preserve_default=False,
       ),
   ]           

【问题讨论】：

您的迁移有问题吗？

你能给我们看看 autotester.0005_auto_20150519_1831 吗？

【参考方案1】：

OneToOneField 类似于 ForeignKey 和 unique=True。

您的问题与此唯一约束有关，因为如果您的数据库不为空，则无法添加具有唯一约束的字段。你要做的是：

添加没有唯一约束的字段 = ForeignKey 填写此字段，了解即将到来的唯一约束 将 ForeignKey 更改为 OneToOneField

详细步骤如下：

第一步：

删除您的 autotester/migrations/0005_auto_20150519_1831.py 文件并在您的 result = models.ForeignKey(Result, null=True, blank=True) 模型中将您的 result 字段更改为 TestExecution 并进行迁移：

./manage.py makemigrations autotester
./manage.py migrate autotester

第二步：

对于您拥有的每个Result，创建一个TestExecution（将 FOO 替换为适当的数据）：

results = Result.objects.all()

for result in results:
    tst = TestExecution()
    tst.name = FOO
    tst. num_testsuites = FOO
    tst.time = FOO
    tst.result_id = result.id
    tst.save()

第三步

使用result = models.OneToOneField(Result) 更改您的结果字段，然后进行迁移：

./manage.py makemigrations autotester
./manage.py migrate autotester

你应该很高兴。

【讨论】：

删除result = models.OneToOneField(Result)?

迁移成功了……我现在正在解析我的 xml 测试结果！完成后我会在那里发帖

我认为它不起作用...Unknown column 'autotester_testexecution.result_id' in 'where clause'