我有一个这样的模型：

class AssignedTip(models.Model):
    """Model representing a tip (but not a specific copy of a tip)."""
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    date = models.DateField(null=True)
    note = models.CharField(max_length=50, default="Tip")
    amount = models.FloatField()
    minutes = models.FloatField(default=0)

    class Meta:
        unique_together = ('user', 'date',)

所以user+date存在唯一约束。
现在我想在表中插入新数据。但是如果唯一约束匹配，则应该更新对象而不是创建新对象。我怎么能这样做。使用create_or_update给了我一个错误，并没有更新项目。如果约束匹配，我如何告诉它更新？：

AssignedTip.objects.update_or_create(user=User.objects.get(id=user), amount=user_amount, date=day.date(), minutes=minutes)

我得到这个错误：

Environment:

Request Method: GET
Request URL: http://0.0.0.0:8000/tasks/

Django Version: 4.0.8
Python Version: 3.10.12
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'widget_tweaks',
 'tasks.apps.TasksConfig',
 'tips.apps.TipsConfig',
 'ratings.apps.RatingsConfig',
 'procedures.apps.ProceduresConfig',
 'inventory.apps.InventoryConfig',
 'registration.apps.RegistrationConfig',
 'ckeditor',
 'crispy_forms',
 'crispy_bootstrap4',
 'django_crontab']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'whitenoise.middleware.WhiteNoiseMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 'login_required.middleware.LoginRequiredMiddleware']


Traceback (most recent call last):
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/query.py", line 657, in get_or_create
    return self.get(**kwargs), False
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/query.py", line 496, in get
    raise self.model.DoesNotExist(

During handling of the above exception (AssignedTip matching query does not exist.), another exception occurred:
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/backends/sqlite3/base.py", line 477, in execute
    return Database.Cursor.execute(self, query, params)

The above exception (UNIQUE constraint failed: tips_assignedtip.user_id, tips_assignedtip.date) was the direct cause of the following exception:
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/core/handlers/exception.py", line 55, in inner
    response = get_response(request)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/core/handlers/base.py", line 197, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/raphael/development/iaro/iaroapp/tasks/views.py", line 86, in index
    assignTips(datetime.today().replace(day=7))
  File "/home/raphael/development/iaro/iaroapp/iaroapp/cron.py", line 71, in assignTips
    AssignedTip.objects.update_or_create(user=User.objects.get(id=user), amount=user_amount, date=day.date(), minutes=minutes)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/query.py", line 684, in update_or_create
    obj, created = self.select_for_update().get_or_create(defaults, **kwargs)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/query.py", line 664, in get_or_create
    return self.create(**params), True
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/query.py", line 514, in create
    obj.save(force_insert=True, using=self.db)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/base.py", line 806, in save
    self.save_base(
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/base.py", line 857, in save_base
    updated = self._save_table(
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/base.py", line 1000, in _save_table
    results = self._do_insert(
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/base.py", line 1041, in _do_insert
    return manager._insert(
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/query.py", line 1434, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 1621, in execute_sql
    cursor.execute(sql, params)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/backends/utils.py", line 103, in execute
    return super().execute(sql, params)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/backends/utils.py", line 67, in execute
    return self._execute_with_wrappers(
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/backends/utils.py", line 80, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/backends/utils.py", line 84, in _execute
    with self.db.wrap_database_errors:
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/utils.py", line 91, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)
  File "/home/raphael/.conda/envs/iaro/lib/python3.10/site-packages/django/db/backends/sqlite3/base.py", line 477, in execute
    return Database.Cursor.execute(self, query, params)

Exception Type: IntegrityError at /tasks/
Exception Value: UNIQUE constraint failed: tips_assignedtip.user_id, tips_assignedtip.date