Rails 外键违规删除 has_many 依赖关系销毁

Question

我在 Rails 4.2 模型中有一个简单的 has_many 关系：

class Owner < ActiveRecord::Base
  has_many :nested_things, :inverse_of => :owner, :class_name => "Nested::Thing", :dependent => :destroy
end

class Nested::Thing < ActiveRecord::Base
  belongs_to :owner, :inverse_of=>:nested_things
end

模型比这复杂得多，还有许多其他关系。

今天有人试图删除一个 Owner，但失败了，因为 nested_things table:

上有一个外键

> psql annoying_problem

psql (9.5.3)
Type "help" for help.

annoying_problem=# \d+ nested_things
                                                            Table "public.nested_things"
      Column      |            Type             |                           Modifiers                            | Storage  | Stats target | Description 
------------------+-----------------------------+----------------------------------------------------------------+----------+--------------+-------------
 id               | integer                     | not null default nextval('nested_things_id_seq'::regclass)     | plain    |              | 
 owner_id         | integer                     |                                                                | plain    |              | 

 Indexes:
    "nested_things_pkey" PRIMARY KEY, btree (id)
    "ix_nested_things_on_owner_id" btree (owner_id)
Foreign-key constraints:
    "nested_things_owner_id_fk" FOREIGN KEY (owner_id) REFERENCES owners(id)

删除 owner 时，这是一个耗时的过程 - 此特定记录在本地生成了所有 SQL 执行的 109,000 行日志文件。但是，nested_things 关系导致整个操作中止，因为外键检查失败。

这似乎是日志文件的相关部分：

> grep -n nested_things delete-owner.txt 

....

109762: SQL (1.1ms)  DELETE FROM "nested_things" WHERE "nested_things"."id" =   [["id", 8665]]

109836: ActiveRecord::InvalidForeignKey: PG::ForeignKeyViolation: 
        ERROR:  update or delete on table "owners" violates foreign key 
        constraint "nested_things_owner_id_fk" on table "nested_things"

109837: DETAIL:  Key (id)=(6343) is still referenced from table "nested_things".

此所有者只有一个 nested_things 条目。 什么会导致 Rails 中的 :dependent => :destroy 关系删除依赖关系，但外键检查失败？

Answer 1

原来答案是 has_many 关系的默认范围，在销毁中没有考虑。

Rails 外键违规删除 has_many 依赖关系销毁

Rails Foreign Key violation deleting has_many relationships with dependent destroy

postgresql

activerecord

ruby-on-rails

postgresql-9.5