Refactoring composite primary key to simple key for Rails? - sql

Question

My application uses Ruby on Rails ActiveRecord models, which don't allow for composite keys without installing a third-party gem such as composite-primary-keys. Is there a way I can refactor a composite key into a simple key so it will fit this paradigm, or should I bite the bullet and install the gem?
I'm still at the early design stage so I have no data I need to worry about, and I'd like to stay as true to Rails idioms as possible.
I'm creating a recipe database that can list ingredients and instructions in a step-by-step manner. The database schema is similar to the one shown below, and is using composite keys in the Recipe_Steps and Recipe_Step_Ingredients tables (bottom center of image).

Answer 1

You're very likely overthinking and overcomplicating the problem. Stick with the AR idiom of using a single primary key named id.
For join tables use foreign keys instead of compound PKs. Also stick to the naming conventions unless you want to look inept or annoy other devs by violating the principle of least surprise. That means:
use snake_case for everything (table names, columns, index names etc.)
don't prefix the column with the table name. It just makes every variable in your application longer and is not needed in a ORM.
use _id for foreign key columns. ex; parent_id
use _at for timestamps. ex; confirmed_at
use thing_other_things for join tables unless there is a more descriptive name
Also many of these cases should just use an indirect relation to join up the hierarchy instead of duplicating foreign keys.
This is an example DB schema:
ActiveRecord::Schema.define(version: 20161214013752) do
# These are extensions that must be enabled in order to support this database
enable_extension "plpgsql"
create_table "ingredient_types", force: :cascade do |t|
t.string "name"
t.string "description"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "ingredients", force: :cascade do |t|
t.integer "ingredient_type_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["ingredient_type_id"], name: "index_ingredients_on_ingredient_type_id", using: :btree
end
create_table "recipe_ingredients", force: :cascade do |t|
t.integer "recipe_id"
t.integer "ingredient_id"
t.float "quantity"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["ingredient_id"], name: "index_recipe_ingredients_on_ingredient_id", using: :btree
t.index ["recipe_id"], name: "index_recipe_ingredients_on_recipe_id", using: :btree
end
create_table "steps", force: :cascade do |t|
t.integer "recipe_id"
t.integer "ordinal"
t.text "instruction"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["recipe_id"], name: "index_steps_on_recipe_id", using: :btree
end
create_table "recipes", force: :cascade do |t|
t.string "name"
t.string "description"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
add_foreign_key "ingredients", "ingredient_types"
add_foreign_key "recipe_ingredients", "ingredients"
add_foreign_key "recipe_ingredients", "recipes"
add_foreign_key "steps", "recipes"
end
class IngredientType < ApplicationRecord
has_many :ingredients
end
class Ingredient < ApplicationRecord
belongs_to :ingredient_type
has_many :recipe_ingredients
has_many :recipes, through: :recipe_ingredients
end
class RecipeIngredient < ApplicationRecord
belongs_to :recipe
belongs_to :ingredient
has_one :ingredient_type, through: :ingredient
end
class Step < ApplicationRecord
belongs_to :recipe
end
class Recipe < ApplicationRecord
has_many :recipe_ingredients
has_many :ingredients, through: :recipe_ingredients
has_many :steps
end