dependant: :destroy 导致 postgresql 错误

Question

class Accdist < ActiveRecord::Base
  has_many :accdistlavoraziones, dependent: :destroy

删除 accdist 时，控制台输出以下内容：

 Accdist Load (27.3ms)  SELECT "accdists".* FROM "accdists" WHERE "accdists"."id" =  LIMIT 1  [["id", "1"]]
 Accdistlavorazione Load (20.2ms)  SELECT "accdistlavoraziones".* FROM "accdistlavoraziones" WHERE "accdistlavoraziones"."accdist_id" = 1
  SQL (59.7ms)  DELETE FROM "accdistlavoraziones" WHERE "accdistlavoraziones"."" =   [[nil, nil]]
PG::SyntaxError: ERROR:  zero-length delimited identifier at or near """"
LINE 1: ...OM "accdistlavoraziones" WHERE "accdistlavoraziones"."" = 
                                                                ^
: DELETE FROM "accdistlavoraziones" WHERE "accdistlavoraziones"."" = 
   (0.1ms)  ROLLBACK
Completed 500 Internal Server Error in 155.3ms

奇怪的是，如果我查询：

Accdistlavorazione.where('accdist_id = ?', 1).count
   (0.6ms)  SELECT COUNT(*) FROM "accdistlavoraziones" WHERE (accdist_id = 1)
 => 10

正在返回有效结果。

为什么内部机制导致postgresql处理nil(s)？

Answer 1

对于遇到此问题的任何人，可能发生的情况如下。
- 通过 rails 快捷方式 has_and_belongs_to_many
创建连接 table - 意识到您稍后需要 has_many ... through: 设置
- 在创建新的连接记录时突突突实际运行...因为 [...]_id 正在被引用。
– 删除时间到了，您正在寻找连接的 ID table，自然是 nil

dependant: :destroy 导致 postgresql 错误

dependant: :destroy leading to postgresql error

ruby-on-rails-3.2

postgresql-9.3