Django post_migrate信号被多次调用

Question

我已经创建了一个post_migrate，其目标是在迁移运行时同步表中的所有数据。这是post_migrate文件的片段：

# signals.py
@receiver(post_migrate)
def full_sync_if_model_change(plan, **kwargs):
    if plan:
        models_set = set()
        for file, _ in plan:
            for model in file.operations:
                try:
                    model = SyncModel.objects.get(
                        app_name=file.app_label, model_name=model.model_name
                    )
                    models_set.add(model)
                except ObjectDoesNotExist:
                    pass
        print(models_set)
        if models_set:
            for model in models_set:
                model.set_full_sync()
                run_update_sync(model, False)
        return

但是，当我运行迁移时，它被调用了6次；正如您在迁移的输出中看到的那样：

evandro@evandro-340XAA-350XAA-550XAA:~/Desktop/.../test_service$ python3 manage.py migrateOperations to perform:
  Apply all migrations: admin, auth, contenttypes, django_cron, lakehouse_sync, sessions, test_models
Running migrations:
  Applying test_models.0019_auto_20211026_2052... OK
set()
set()
set()
set()
set()
set()

我还将在此处添加应用程序文件：

class LakeSyncConfig(AppConfig):
    name = "lake_sync"

    def ready(self):
        """Import signals"""
        import lakehouse_sync.core.delete_action

        from . import signals

我不知道该怎么做，我试图添加此返回语句，但它不起作用，因为函数总是被调用。

Answer 1

对于每个迁移的应用程序，即使没有任何更改，也会发送一次post_migrate信号。在连接信号时传递sender参数，以便在应用程序迁移后仅运行函数一次

def full_sync_if_model_change(plan, **kwargs):
    ...


class LakeSyncConfig(AppConfig):
    name = "lake_sync"

    def ready(self):
        post_migrate.connect(full_sync_if_model_change, sender=self)