:dependent => :destroy 销毁不再依赖的记录

Question

Rails 4.2 运行 PostgreSQL

我正在重构我的数据库并移动一些数据。每个ProgressUpdate属于一个LanguageProgress。在迁移中，我将一些 ProgressUpdates 从一个 LanguageProgress 移动到另一个，然后我销毁了不再有任何关联的 ProgressUpdates 的 LanguageProgress，但是销毁会触发销毁ProgressUpdates 那个曾经的依赖吧！这是为什么？

迁移中的相关代码如下：

LanguageProgress.find_each do |lp|
  if existing_lp = LanguageProgress.find_by(progress_marker: lp.progress_marker, language_id: lp.state_language.language_id)
    puts "LanguageProgress #{existing_lp.id} has these ProgressUpdates: #{existing_lp.progress_updates.pluck :id}"
    puts "LanguageProgress #{lp.id} has these ProgressUpdates: #{lp.progress_updates.pluck :id}"
    lp.progress_updates.each do |pu|
      pu.language_progress = existing_lp
      pu.save!
    end
    puts "now LanguageProgress #{existing_lp.id} has these ProgressUpdates: #{existing_lp.progress_updates.pluck :id}"
    puts "and LanguageProgress #{lp.id} has #{lp.progress_updates.count} ProgressUpdates"
    puts "destroying LanguageProgress #{lp.id}"
    lp.destroy
  else
    lp.language_id = lp.state_language.language_id
    lp.save!
  end
end

这是打印出来的内容：

LanguageProgress 1073685945 has these ProgressUpdates: [1071256240]
LanguageProgress 1073691483 has these ProgressUpdates: [1071256239]
now LanguageProgress 1073685945 has these ProgressUpdates: [1071256239, 1071256240]
and LanguageProgress 1073691483 has 0 ProgressUpdates
destroying LanguageProgress 1073691483
destroying ProgressUpdate 1071256239

这是language_progress.rb

的相关部分

class LanguageProgress < ActiveRecord::Base

  belongs_to :language
  belongs_to :state_language
  belongs_to :progress_marker
  has_many :progress_updates, dependent: :destroy

  validates :progress_marker, presence: true, uniqueness: { scope: :state_language }
  validates :state_language, presence: true

和progress_update.rb

class ProgressUpdate < ActiveRecord::Base

  belongs_to :user
  belongs_to :language_progress
  delegate :language, to: :language_progress

  validates :progress, presence: true, inclusion: ProgressMarker.spread_text.keys
  validates :month, presence: true, inclusion: 1..12
  validates :year, presence: true, inclusion: 2000..Time.now.year
  validates :user, presence: true
  validates :language_progress, presence: true

  before_destroy{ |pu| puts "destroying ProgressUpdate #{pu.id}" }

end

Answer 1

我猜测，我会尝试在移动其他进程后（并在销毁它之前）重新加载 lp。

实例变量可能包含对它认为仍然属于它的进程的引用（即使它们不再存在）。

:dependent => :destroy 销毁不再依赖的记录

:dependent => :destroy destroys records that are no longer dependents

postgresql

ruby-on-rails

relational-database