Counter Cache for a column with conditions?

Question

I am new to the concept of counter caching and with some astronomical load times on one of my app\'s main pages, I believe I need to get going on it.

Most of the coun

Answer 1

You should not use "counter_cache" but rather a custom column :

rails g migration AddCompletedProjectsCountToEmployees completed_projects_count:integer

(add , :default => 0 to the add_column line if you want)

rake db:migrate

then use callbacks

class Project < ActiveRecord::Base
  belongs_to :employee

  after_save :refresh_employee_completed_projects_count
  after_destroy :refresh_employee_completed_projects_count

  def refresh_employee_completed_projects_count
    employee.refresh_completed_projects_count
  end
end

class Employee
  has_many :projects

  def refresh_completed_projects_count
    update(completed_projects_count:projects.where(completed:true).size)
  end
end

After adding the column, you should initialize in the console or in the migration file (in def up) :

Employee.all.each &:refresh_completed_projects_count

Then in your code, you should call employee.completed_projects_count in order to access it