delete_instance with recursive=True only works with one level

I have a table with foreign key to itself

class Post(BaseModel):
    reply_to: Post = ForeignKeyField(
        'self', null=True, default=None, backref='child_posts', on_delete='CASCADE')

Then in db if i have

id reply_to_id
1 nulll
2 1
3 2
4 3
5 4

If i delete_instance(True, True) record id=2, it deletes ID 2,3 only and leave ID 4,5. It means it doesn’t delete recursively (only works for 1 level).

Did i miss something or i have to deploy delete recursively by myself?

[coleifer]

I remembered that the other - in fact, main - reason for not supporting this is that we don’t know how deep into the graph to go without resolving foreign-keys at every step.

So with a non-self-referential graph of foreign-keys, we just make sure to issue a query for each node in the graph (each foreign-key). With self-referential, we would have to issue n deletes where n is the maximum depth of any row’s relations. But we don’t know how far to go without resolving at each step. So peewee doesn’t do this, but you could very easily write it yourself.

Or just use the database. The database knows how to delete a self-referential collection of rows. That is why the ON DELETE constraint exists. Use it!

I prefer to do delete on code rather than depend on db.

Why? To my thinking that’s 100% backwards.

[dzpt]

avoid cycles in the dependency graph.

Can we check the type of foreign key before deleting, it would avoid circular delete? I prefer to do delete on code rather than depend on db.