Polymorphic Association Rails : Different primary_keys types (id & uuid)

Question

I would like to define a polymorphic table. My problem being that one table's primary_key is of type uuid(string) and the other id(integer) . I thought maybe having a model_able_id and a model_able_uuid varying depending on the model_type but i cannot figure that out and it would probably break tons of activerecord features for polymorphic.

Some other things i have thought of would be to use STI, but i'm still confused, and, of course, i could migrate ids to uuids and that'd sort me out (but i'd rather not).

Answer 1

Specify the type for the (polymorphic) foreign key in the options. Change :string to :uuid if required.

create_table :table_name do |t|
  t.references :target, type: :string, polymorphic: true, null: false
end

Then both string and integer target_id s are acceptable.

Check the API docs .

Answer 2

Was facing same issue, there is no official solution yet, these two issues are open in rails repo about this:

https://github.com/rails/rails/issues/33407

https://github.com/rails/rails/issues/33525

There is a suggestion in one of these issues , it didn't work for me(it was generating both joins, the default one generated by rails which causes failure and one which i defined).

I ended up not using association at all, i defined a method to get the actual records properly with a custom query. I didn't need dependent: destroy otherwise i could have defined a before_destroy method too.

Hope it helps someone.

Answer 3

I had exactly the same problem. My solution modifies the type of the _id field to string.

def change
  add_reference :ratings, :rater, polymorphic: true, index: true
  change_column :ratings, :rater_id, :string
end

I hope it helps.