Jani Tiainen wrote:
> Michael Glassford kirjoitti:
>>
>> Alex Gaynor wrote:
>>
>>> Can you upload it with a .diff extension so we can get proper code
>>> highlighting on trac.
>>>
>>> Alex
>>>
>> Sorry. Done.
>
> I did a quick look and what I understand now it only supports client
> side on_delete actions (cascade, protect (restrict), set null and set
> default)?
Yes.
> I assume that None means not specified on_delete (old way).
Yes.
> Could that
> translation to CASCADE or SET_NULL activity made in field construction
> phase?
> Or is there need to have explicitly define on_delete=None?
No.
> Only thing I'm a bit worried is a performance. I have model like
> following (legacy model):
>
> class Device(models.Model):
> name = models.CharField()
>
> class Connector(models.Model):
> device = models.ForeignKey(Device, on_delete=CASCADE)
> type = models.CharField()
>
> class Connection(models.Model):
> connector_1 = models.ForeignKey(Connector, on_delete=CASCADE)
> connector_2 = models.ForeignKey(Connector, on_delete=CASCADE)
> direction = models.CharField()
>
> class Route(models.Model):
> name = models.CharField()
>
> class RouteConnection(models.Model):
> route = models.ForeignKey(Route, on_delete=PROTECT)
> connection = models.ForeignKey(Connection, on_delete=PROTECT)
>
>
> Now I have one device that contains 1000 connectors. Each connection has
> at least 1 connection. And one connection has one route attached to it
> (using RouteConnection).
>
> I want to delete this partical device.
>
> In worst case does system need to traverse over all 999 connections
> before hitting one that says we can't delete device?
Unfortunately, yes. I realize that the ideal situation is to allow the
backend to handle this if it can, since it can do so more efficiently,
but I didn't think that feature could be ready for the Django 1.2. So I
decided that something is better than nothing and went for a phased
approach. I hope to add backend support in a later version of Django.
Mike
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