You could try using update_columns
which will update the database directly without performing any callbacks or validation:
Design.first.update_columns(targetable_id: 1, targetable_type: "Collection")
However, if it were me, I'd try to figure out exactly why it's failing... If you try:
Design.first.update_attributes!(targetable_id: 1, targetable_type: "Collection")
... the console should give you additional information as to why it's failing, which may help you run update_attributes
.