.diff

class CreateRecommendations < ActiveRecord::Migration[5.2]
   def change
-     create_table :recommendations do |t|
+     create_table :recommendations, id: false do |t| # idの代わりにuidを使う
-     t.bigint :uid
+     t.bigint :uid, null: false, unique: true
-     t.blob :recommended_id_list
+     t.blob :recommended_id_list,  null: false
-     t.timestamps
+     t.datetime :updated_at, null: false # created_atは不要
    end
   end
-  add_index :recommendations, :uid
+  add_index :recommendations, :uid, unique: true
+  add_index :recommendations, :updated_at, unique: true
 end