到目前为止，我正在使用的方法，似乎工作可靠，是为模型示例化一个本地Manager，然后将manager的model属性设置为我感兴趣的模型：

class MyManager(Manager):
    ...
    def my_create_func(self):
        ...

class MyModel(Model):
    ...
    objects = MyManager()

def data_migration(apps, schema_editor):
    model = apps.get_model(...)
    manager = MyManager()
    manager.model = model
    manager.my_create_func()

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您还可以使用Manager的use_in_migrations属性（docs）：

class MyManager(models.Manager):
    use_in_migrations = True

class MyModel(models.Model):
    objects = MyManager()

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为什么不直接导入你的模型？

from myproj.models import MyModel
MyModel.objects.filter(field=value).update(field=new_value)

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这让我今天。

如何在自定义RunPython Django迁移中使用自定义管理器的方法

假设你已经有了这个模型及其自定义管理器：

# e.g. in myapp.managers file
class MyModelManager(models.Manager):
    def do_something_special():
        # ... your clever database manipulation

# in myapp.models file
class MyModel(models.Model):
    #... various fields

    objects = MyModelManager()

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当您试图通过直接将Model导入到迁移中来使用它时，会发生这样的错误：

def my_custom_migration_function__forwards(apps, schema_editor):
    from myapp.models import MyModel
    MyModel.objects.do_something_special()  # Custom Manager method

class Migration(migrations.Migration):

    dependencies = [
        ('myapp', '0001_an_earlier_migration')
    ]

    operations = [
        #... Other migration steps such as CreateModel or AddField etc...,
        migrations.RunPython(my_custom_migration_function__forwards, reverse_code=migrations.RunPython.noop)
    ]

# Raises: 
#    'do_something_special': Could not find an 'apps.get_model("...", "MyModel")'
#    Importing the model directly is incorrect for data migrations.
#    'do_something_special': Model variable name MyModel is different from the model class name that was found in the apps.get_model(...)

型
当你有一个自定义的模型方法，而迁移看不到的时候，会发生这样的错误：

def my_custom_migration_function__forwards(apps, schema_editor):
    MyModel = apps.get_model('myapp', 'MyModel')
    MyModel.objects.do_something_special()  # Custom Manager method

# Raises: *AttributeError: Manager has no do_something_special*

型
在43TesseractsAnswer的基础上，解决方案分为四个部分：

A）将use_in_migrations = True放入Manager类中：

# e.g. in myapp.managers.py file
class MyModelManager(models.Manager):
    use_in_migrations = True   # << Add this

型

B）在终端中使用makemigrations生成迁移

./manage.py makemigrations

型
您会发现一个新的迁移是由一个migrations生成的。

C）移植迁移，AlterModelManagers从新的迁移迁移到您自定义迁移的正确位置：

def my_custom_migration_function__forwards(apps, schema_editor):
    from myapp.models import MyModel
    MyModel.objects.do_something_special()  # Custom Manager method

class Migration(migrations.Migration):

    dependencies = [
        ('myapp', '0001_an_earlier_migration')
    ]

    operations = [
        #... Other migration steps such as CreateModel or AddField etc...,
        migrations.AlterModelManagers(  # << GRAFT THIS IN
            name='mymodel',
            managers=[
                ('objects', 
myapp.managers.MyModelManager()),
            ],
        ),
        migrations.RunPython(my_custom_migration_function__forwards, reverse_code=migrations.RunPython.noop)
    ]

型

D）删除自动创建的迁移

您已经将该步骤移植到早期的迁移中，因此不再需要它。