删除记录时出现外键约束错误

我得到一个外键约束错误,它说明:

ActiveRecord::InvalidForeignKey: PG::ForeignKeyViolation: ERROR:  update or delete on table "users" violates foreign key constraint "fk_rails_5b5ddfd518" on table "posts"
DETAIL:  Key (id)=(950961012) is still referenced from table "posts".

所以我的post表引用了一个用户表条目,但是当用户被删除时,我不希望用户的文章也被删除。所以会发生什么:仍然有一个对不存在的用户的引用。

我希望在删除用户时断开该关系,并保留用户的日志,也许可以通过将用户引用设为零

这是我的一个摘录 图RB

  create_table "posts", force: :cascade do |t|
    t.bigint "user_id"
    t.string "title"
    t.text "body"
    t.string "category"
    t.string "slug"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["category"], name: "index_posts_on_category"
    t.index ["slug"], name: "index_posts_on_slug", unique: true
    t.index ["user_id"], name: "index_posts_on_user_id"
  end

  create_table "users", force: :cascade do |t|
    t.string "name"
    t.string "email"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "password_digest"
    t.string "slug"
    t.string "remember_digest"
    t.boolean "admin", default: false
    t.string "activation_digest"
    t.boolean "activated", default: false
    t.datetime "activated_at"
    t.string "reset_digest"
    t.datetime "reset_sent_at"
    t.index ["email"], name: "index_users_on_email", unique: true
    t.index ["name"], name: "index_users_on_name", unique: true
    t.index ["slug"], name: "index_users_on_slug", unique: true
  end

用户地址 :

class User < ApplicationRecord
  ...
  has_many :posts
  ...

邮政银行 :

class Post < ApplicationRecord
  ...
  belongs_to :user
  ...
end