Ruby：表上的更新或删除违反了外键约束

Question

我目前在运行时遇到此错误

Shop.last.destroy

，但我不明白为什么：

PG::ForeignKeyViolation: ERROR:  update or delete on table "credit_changes" violates foreign key constraint "fk_rails_16918229d0" on table "sms_historicals" (ActiveRecord::InvalidForeignKey)

这是一个 Postgres 数据库

我的模型看起来像这样：

class SmsHistorical < ApplicationRecord
  belongs_to :customer
  belongs_to :credit_change, optional: true
  belongs_to :notification_setting, optional: true
end

class CreditChange < ActiveRecord::Base 
  belongs_to :credit
  belongs_to :customer
  has_one :sms_historicals
  has_one :email_historicals
end

创建这些表的迁移如下：

create_table :credit_changes, if_not_exists: true do |t|
  t.integer "credit_id"
  t.text "credit_notes"
  t.decimal "credit_amount_changed", precision: 4, scale: 2, default: 0.0
  t.datetime "date"
  t.string "transaction_type"
  t.datetime "created_at", null: false
  t.datetime "updated_at", null: false
end

class CreateSmsHistoricals < ActiveRecord::Migration[6.1]
  def change
    create_table :sms_historicals, if_not_exists: true do |t|
      t.string :phone_number
      t.text :message
      t.references :customer, null: true, foreign_key: true, on_delete: :cascade
      t.references :credit_change, null: true, foreign_key: true, on_delete: :cascade
      t.references :notification_setting, null: true, foreign_key: true, on_delete: :cascade
      t.timestamps
    end
  end
end

Answer 1

belongs_to :credit_change

是 Sms 和 Credit 表之间的 FK。 Credit ID 存储在Sms 表中。当您尝试删除Credit时，还需要清除Sms表中的数据。例如

class CreditChange < ActiveRecord::Base 
  has_one :sms_historicals, dependent: :nullify
end

我在这里选择

:nullify

，因为您在短信表上将

belongs_to :credit_change

设置为可选。但也可以是其他东西：https://guides.rubyonrails.org/association_basics.html#options-for-has-one