Rails 6.1.4 counter_cache 问题

Question

我开发了具有 Issue 和 IssueStep 模型的简单应用程序。我不确定我是否错过了 counter_cache 的某些内容，因为对于使用自定义名称和 class_name.

定义的关系，它无法按预期工作

issue.steps.size - fire count() in DB, why? 
issue.issue_steps.size - uses counter_cache
issue.issue_steps_count - has correct values and I use it now

class IssueStep < ApplicationRecord
  belongs_to :issue, counter_cache: true
end

class Issue < ApplicationRecord
  has_many :steps, class_name: 'IssueStep', foreign_key: 'issue_id', dependent: :destroy
  has_many :issue_steps # added for test only 
end

Answer 1

这是你必须做的才能让它发挥作用

将 Issue table 中的计数器列名称更改为 steps_count
在 IssueStep 模型中用以下代码替换您的代码

  belongs_to :issue, counter_cache: :steps_count

现在您应该可以使用 issue.steps.size

获取缓存值

This is how Rails find the cached column name: link to official source code

Rails 6.1.4 counter_cache 问题

Rails 6.1.4 counter_cache issue

ruby-on-rails

counter-cache