我如何创建一个带有外键的 Django 模型，它不会将删除级联到它的孩子?

How do I create a Django model with ForeignKeys which does not cascade deletes to its children?(我如何创建一个带有外键的 Django 模型，它不会将删除级联到它的孩子?)

问题描述

我的一个具有 ForeignKey 的模型实际上是其他表上的 MySQL 视图.我遇到的问题是，当我从这些表中删除数据时，Django，如 "删除对象" 文档...

One of my models which has ForeignKey's is actually a MySQL view on other tables. The problem I'm running into is that when I delete data from these tables, Django, as described in the "deleting objects" documentation...

当 Django 删除一个对象时，它模拟 SQL 的行为约束 ON DELETE CASCADE -- in换句话说，任何具有指向对象的外键被删除将被删除

When Django deletes an object, it emulates the behavior of the SQL constraint ON DELETE CASCADE -- in other words, any objects which had foreign keys pointing at the object to be deleted will be deleted along with it.

...试图从我的视图中删除行，这当然不能，因此引发错误:

...tries to remove rows from my view, which of course it can't, and so throws the error:

mysql_exceptions.OperationalError '>=(1395, "Can not delete from join view 'my_db.my_mysql_view'"'

有什么方法可以在模型上指定 ForeignKey 约束，它会为我提供所有 Django 魔法，但不会级联删除到它上面?或者，有没有办法让 MySQL 忽略从我的视图中删除一行的命令而不是引发错误?

Is there any way to specify a ForeignKey constraint on a model which will provide me with all the Django wizardry, but will not cascade deletes onto it? Or, is there a way to ask MySQL to ignore the commands to delete a row from my view instead of raising an error?

推荐答案

Harold 的回答为我指明了正确的方向.这是我实现它的方式的草图(在法国遗留数据库上，因此命名约定有点奇怪):

Harold's answer pointed me in the right direction. This is a sketch on the way I implemented it (on a french legacy database, hence the slightly odd naming convention):

class Factures(models.Model):
    idFacture = models.IntegerField(primary_key=True)
    idLettrage = models.ForeignKey('Lettrage', db_column='idLettrage', null=True, blank=True)

class Paiements(models.Model):
    idPaiement = models.IntegerField(primary_key=True)
    idLettrage = models.ForeignKey('Lettrage', db_column='idLettrage', null=True, blank=True)

class Lettrage(models.Model):
    idLettrage = models.IntegerField(primary_key=True)

    def delete(self):
        """Dettaches factures and paiements from current lettre before deleting"""
        self.factures_set.clear()
        self.paiements_set.clear()
        super(Lettrage, self).delete()

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