AnaReis skrev:
> Hi all!
> I have a delete that isn't working properly. It deletes more than 1
> register when it shouldn't because I'm specifying the primary key in
> the filter.
> The class file is this:
> class UserInstrument(models.Model):
> user_name = models.CharField(primary_key=True, maxlength=60)
> instrument_name = models.CharField(blank=False, maxlength=60)
> permission = models.TextField(blank=True)
> def __str__(self):
> string="user_name: "+self.user_name+"; instr_name:
> "+self.instrument_name+"; permission: "+self.permission
> return string
> class Meta:
> db_table = 'User_instrument'
> unique_together = (("user_name", "instrument_name"),)
> In the view function I'm doing this:
> UserInstrument.objects.filter(user_name__exact=username,
> instrument_name__exact=itemid).delete()
>
> Oh and another detail, in the MySQL table, the primary key is the
> user_name and the instrument_name together.
>
I am not sure whether this is the cause of your problem, but
- Django doesn't support multi-field primary keys
- Your model class tells Django that "user_name" alone is the primary
key, which is wrong (and will lead to strange primary key lookups).
- Django implements its own cascading delete, independent of the
database. In this I believe it loops throught the queryset, and deletes
the objects based on the primary key. Since you "lied" to it about what
the PK is, it deletes the wrong objects.
Quick solution: Remove the primary_key=True from the model - this will
add the standard "id" autonumber field.
Slow solution: Add support for multi-field primary keys to the database.
Nis
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