Deleting rails active records with delete_all/delete violates foreign key constraint

On Postgres you can use the CASCADE option on the foreign key itself.

CASCADE specifies that when a referenced row is deleted, row(s) referencing it should be automatically deleted as well.
- https://www.postgresql.org/docs/9.5/ddl-constraints.html

This is usually setup when creating the table but you can add it to an exisiting table by removing and then re-adding the foreign key constraint:

class AddCascadeToOrderItems < ActiveRecord::Migration[6.0]
  def up
    remove_foreign_key :order_items, :orders
    add_foreign_key :order_items, :orders, on_delete: :cascade
  end

  def down
    remove_foreign_key :order_items, :orders
    add_foreign_key :order_items, :orders
  end
end

Since this is handled on the DB level no configuration is needed in your model.

has_many :inventory_items, dependent: :delete_all

Works as well and is the only option on peasant databases like MySQL but it will only be fired when you call .destroy and not .delete on the model that declares the association as its implemented as a model callback. For example:

class Store < ApplicationRecord
  has_many :inventory_items, dependent: :delete_all
end

store = Store.find(1)
store.destroy # triggers callbacks and will delete all assocatiated inventory_items
store.delete  # will not trigger callbacks