Question

In django, I want to copy data from identical tables in one db to those in another — from ‘db01’ to ‘default’. Schema are identical.

>>> a=Household.objects.filter(h_identifier='H122000-48').using('db01')
>>> a[0].pk
>>> u'451465ea-0137-11e0-879a-70f1a16e0f80'
>>> a[0].save(using='default')
>>> b=Household.objects.filter(h_identifier='H122000-48').using('default')
>>> b[0].pk
>>> u'7c2484fe-8641-11e0-b080-00188b4d6b0e'

it works but the primary key for the record inserted into ‘default’ is not the same as the one fetched from ‘db01’. To maintain integrity with other tables, the pk must not change. The django docs section selecting-a-database-for-save suggests that since instance ‘a’ already has a primary, the same primary key will be used when a new record is inserted to ‘default’. I cannot get it to do that.

Does anyone know if this can be done? thanks in advance!!

(This may seem like an odd setup, but the application runs independently on disconnected netbooks during the day, and data is merged into a master db during the night when all the netbooks are docked. I can do it fine in mysql but would like to use the django ORM if possible.)

Answer 1

I know this is from a while ago, but I had the same issue today – judging by the key you’re using, your id field is of type UUIDField from django_extensions?

It’s slightly buggy, as the pre_save signal will always ensure the key is replaced regardless of whether there’s one already existing. Subclassing it and replacing the pre_save function fixes it.

class FixedUUIDField(UUIDField):
def pre_save(self, model_instance, add):
    value = super(UUIDField, self).pre_save(model_instance, add)
    if self.auto and add and not value:
        value = unicode(self.create_uuid())
        setattr(model_instance, self.attname, value)
    return value