Admin save of non-default database model fails when model contains unique fields

[jay@…]

When I created the appropriate ​admin.ModelAdmin , pointing to a different database (non-default), querying the database worked correctly. However, when trying to save, it would fail with the following message:

(1146, "Table 'django_dev._Transactions' doesn't exist")

The problem is that django_dev is the default database, not the database specified in the ModelAdmin. Here's my model admin definition:

class TransactionAdmin(admin.ModelAdmin):
    using = "salesdb"

    def save_model(self, request, obj, form, change):
        # Tell Django to save objects to the 'other' database.
        obj.save(using=self.using)

    def delete_model(self, request, obj):
        # Tell Django to delete objects from the 'other' database
        obj.delete(using=self.using)

    def queryset(self, request):
        # Tell Django to look for objects on the 'other' database.
        return super(TransactionAdmin, self).queryset(request).using(self.using)

    def formfield_for_foreignkey(self, db_field, request=None, **kwargs):
        # Tell Django to populate ForeignKey widgets using a query
        # on the 'other' database.
        return super(TransactionAdmin, self).formfield_for_foreignkey(db_field, request=request, using=self.using, **kwargs)

    def formfield_for_manytomany(self, db_field, request=None, **kwargs):
        # Tell Django to populate ManyToMany widgets using a query
        # on the 'other' database.
        return super(TransactionAdmin, self).formfield_for_manytomany(db_field, request=request, using=self.using, **kwargs)

and here is my model definition (simplified):

class Transaction(models.Model):
    transactionId = models.IntegerField(primary_key=True, db_column='_TransactionID')
    transactionDate = models.DateField("Transaction date", db_column='_TransactionDate', default=datetime.now())
    customer = models.ForeignKey(Customer, db_column='_CustomerID')
    quantity = models.IntegerField(db_column='_Quantity', default=1)
    regName = models.CharField("Registered name", max_length=240, db_column='_RegName')
    regProdCode = models.CharField("Registered product", max_length=12, db_column='_RegProdCode', choices=PROD_CODE_CHOICES, default="INDM")
    regDate = models.DateField("Registration date", db_column='_RegDate', default=datetime.now())
    regKey = models.CharField("Registration code", max_length=90, db_column='_RegKey', blank=True, unique=True) # PROBLEM IS HERE
    ipAddress = models.GenericIPAddressField("IP address", max_length=60, db_column='_IPAddress', blank=True)

    def __unicode__(self):
        if self.transactionId:
            return "%i" % (self.transactionId,)
        return "None"

    class Meta:
        db_table = u'_Transactions'

I found that I had a field that was marked unique=True in the model. If I remove that, then everything works. I also used PyCharm to trace the problem into the code that was checking the uniqueness of the fields. The very odd thing is that if I break before the problem occurs, then step through it, it will in fact work. But when running with no breakpoints it fails every time. Not sure what that indicates.

I can provide the full model if it will help - it's just pretty large.

[Tim Graham]

This seems likely to be a duplicate of #15130 -- Model.validate_unique() isn't multi-db aware.