我有一个属性为DateTimeField的对象，现在我想将其更改为DateField.
但是我的数据库中已经有数据，所以只需执行此迁移:
migrations.AlterField(
model_name='assignedtip',
name='date',
field=models.DateField(),
),
不会起作用的，因为后来桌子被打破了.
如何确保在使用makemigration执行此迁移时，首先将DateTimeField值转换为DateFields？
我认为分四步来做可能更好:
NULL的字段assignedtip_date；assignedtip的截断部分填充字段；assginedtip字段；以及assginedtip_date字段重命名为assignedtip.因此，迁移将如下所示:
# app_name/migrations/0123_some_name.py
from django.db import migrations, models
from django.db.models.functions import TruncDate
def migrate_date(apps, schema_editor):
MyModel = apps.get_model("app_name", "MyModel")
MyModel.objects.update(assignedtip_date=TruncDate('assignedtip'))
class Migration(migrations.Migration):
dependencies = [("migrations", "0001_initial")]
operations = [
migrations.AddField(
"MyModel", "assignedtip_date", models.DateField(null=True)
),
migrations.RunPython(migrate_date),
migrations.RemoveField("MyModel", "assignedtip"),
migrations.RenameField("MyModel", "assignedtip_date", "assignedtip"),
]