Index error in the uniqueness of two columns

Question

I created to tables:

class CreateWines < ActiveRecord::Migration[6.1]
  def change
    create_table :wines do |t|
      t.string :name
      t.string :producer

      t.timestamps
    end
  end
end

class CreateWineItems < ActiveRecord::Migration[6.1]
  def change
    create_table :wine_items do |t|
      t.references :wine, null: false, foreign_key: true
      t.string :vintage

      t.timestamps
    end
    add_index :wine_items, [:wine, :vintage], unique: true
  end
end

Adding the index for te uniqueness of two columns. In the WineItem model I added the validation:

validates :wine, uniqueness: {scope: :vintage}

I can insert a WineItem

WineItem.create(wine_id: 1, vintage: "2018")

but if I try another Wine with the same vintage an Unique constraint failed:

WineItem.create(wine_id: 2, vintage: "2018")
ActiveRecord::RecordNotUnique (SQLite3::ConstraintException: UNIQUE constraint failed:
 index 'index_wine_items_on_wine_and_vintage')

I only want not to insert same wines with same vintage, and all the references tell me this is the way.

Thanks in advance

Just out of courisity - why is vintage a string and not an integer? — max
– max, Commented Jul 24, 2021 at 10:02

Lam Phan · Accepted Answer · 2021-07-24 09:10:01Z

2

the uniqueness is the helper validates that the attribute's value is unique, so your validation should be

validates :wine_id, uniqueness: {scope: :vintage}

edited Jul 24, 2021 at 9:10

answered Jul 24, 2021 at 9:00

Lam Phan

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1 Comment

John Fadria Over a year ago

Yes and the index should be add_index :wine_items, [:wine_id, :vintage], unique: true

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