由于 Ruby 和 Rails 中的外键约束，为什么用于为数据库播种的 rake 文件无法工作？

Question

我已经用 Rails 6 创建了一个虚拟旅行社，我正在尝试使用 rake 文件为船舶、邮轮和客户详细信息等播种数据。

文件：ships.rake 看起来像这样：

namespace :ships do
  desc "TODO"
  task seed_cabins: :environment do
    CreditCard.destroy_all
    Address.destroy_all
    Customer.destroy_all
    Cruise.destroy_all
    Ship.destroy_all

    p "tables emptied"
  
    5.times do |index|
      Ship.create!(name: Faker::Coffee.blend_name, tonnage: Faker::Number.within(range: 10000..100000))
    end

    p "ships created"
    
    # create cabins for each ship
    ships = Ship.all
    ships.each do |ship|
      5.times do |index|
        Cabin.create!(
          ship_id: ship.id,
          name: "Suite #{index+1}",
          beds: Faker::Number.between(from: 1, to: 3),
          deck: Faker::Number.between(from: 1, to: 3)
        )
      end
    end
    
    p "Cabins created"
    ships = Ship.all
    ships.each do |ship|
      2.times do |index|
        Cruise.create!(
          ship_id: ship.id,
          name: Faker::Hacker.adjective.capitalize + " " +Faker::Hacker.noun.capitalize+" Cruise"
        )
      end
    end
    
  #create customers
    3.times do |index |
      Customer.create!(
        first_name:Faker::Name.first_name,
        last_name:Faker::Name.last_name,
       has_good_credit: true,
        paid: false
      )
    end

   #give each customer an addresses and credit card
    customers = Customer.all
    customers.each do | customer|
      Address.create!(
      street:Faker::Address.street_address,
      city:Faker::Address.city,
      postcode:Faker::Address.postcode,
      customer_id: customer.id
      )
      year = [2020, 2021,2022, 2023]
      organisations =["American Express", "MasterCard", "Visa"]
      CreditCard.create!(
        customer_id:customer.id,
        number:Faker::Number.number(12),
        exp_date:year.sample.to_s + "/" + Faker::Number.between(1,12).to_s,
       name_on_card: customer.first_name + " " + customer.last_name,
       organisation: organisations.sample.to_s
      )
    end
    p "customers created"
  end
end

数据库模式如下所示：

ActiveRecord::Schema.define(version: 2020_10_27_221059) do

  create_table "addresses", force: :cascade do |t|
    t.string "street"
    t.string "city"
    t.string "postcode"
    t.integer "customer_id", null: false
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["customer_id"], name: "index_addresses_on_customer_id"
  end

  create_table "cabins", force: :cascade do |t|
    t.string "name"
    t.integer "beds"
    t.integer "deck"
    t.integer "ship_id", null: false
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["ship_id"], name: "index_cabins_on_ship_id"
  end

  create_table "credit_cards", force: :cascade do |t|
    t.string "number"
    t.string "exp_date"
    t.string "name_on_card"
    t.string "organisation"
    t.integer "customer_id", null: false
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["customer_id"], name: "index_credit_cards_on_customer_id"
  end

  create_table "cruises", force: :cascade do |t|
    t.string "name"
    t.integer "ship_id", null: false
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["ship_id"], name: "index_cruises_on_ship_id"
  end

  create_table "customers", force: :cascade do |t|
    t.string "last_name"
    t.string "first_name"
    t.integer "has_good_credit"
    t.boolean "paid"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
  end

  create_table "harbours", force: :cascade do |t|
    t.string "name"
    t.string "country"
    t.string "lat"
    t.string "long"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
  end

  create_table "ships", force: :cascade do |t|
    t.string "name"
    t.integer "tonnage"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
  end

  add_foreign_key "addresses", "customers"
  add_foreign_key "cabins", "ships"
  add_foreign_key "credit_cards", "customers"
  add_foreign_key "cruises", "ships"
end

本质上，我只是尝试运行命令：rake ships:seed_cabins 并尝试生成新鲜的数据。但是，我不断收到以下错误：

rake aborted!
ActiveRecord::InvalidForeignKey: SQLite3::ConstraintException: FOREIGN KEY constraint failed
/home/jonathon/Projects/waad/RailsApps/travelagent/lib/tasks/ships.rake:8:in `block (2 levels) in <main>'

Caused by:
SQLite3::ConstraintException: FOREIGN KEY constraint failed
/home/jonathon/Projects/waad/RailsApps/travelagent/lib/tasks/ships.rake:8:in `block (2 levels) in <main>'
Tasks: TOP => ships:seed_cabins
(See full trace by running task with --trace)

我知道销毁表的顺序是个问题，当前顺序是我能找到的最接近文件正常工作的顺序。这似乎是 Ship.destroy_all 行的问题，因为当我删除它和运行文件时，它运行没有问题！

但是，据我所知，一旦其他表被清除，该数据库将不会留下任何约束，这将阻止 Ship 被删除？

如果有人能指出正确的方向，我将不胜感激。

Answer 1

你错过了摧毁小木屋的机会，它们仍然引用船只作为外键。因此外键约束开始起作用。

附带说明一下，您可以通过在关联中添加 dependent: :destroy 让您的生活更轻松。例如，在您的 Ship 模型中，您将添加

class Ship < ApplicationRecord
  has_many :cabins, dependent: :destroy
end

因为没有相应的船，舱室就没有意义。这样做的目的是，每当一个 Ship 实例被销毁时，它也会同时销毁相关的舱室。

由于 Ruby 和 Rails 中的外键约束，为什么用于为数据库播种的 rake 文件无法工作？

Why will a rake file used to seed a datbase not work due to foreign key constraints in Ruby on Rails?

database

sqlite

activerecord

ruby-on-rails