哪个 rails query/chain 更好？

Question

我有一个 rails 应用程序，其中包含以下型号。对于给定用户，我同时拥有 assigned_tasks 和 executed_tasks。我想知道哪个选项更适合为给定用户获取所有任务（也执行和分配）。

task.rb

belongs_to :assigner, class_name: "User"
belongs_to :executor, class_name: "User"

user.rb

has_many :assigned_tasks, class_name: "Task", foreign_key: "assigner_id", dependent: :destroy
has_many :executed_tasks, class_name: "Task", foreign_key: "executor_id", dependent: :destroy

解决方案 1:

task.rb

scope :completed, -> { where.not(completed_at: nil) }
scope :uncompleted, -> { where(completed_at: nil) }

user.rb

def tasks_uncompleted
  tasks_uncompleted = assigned_tasks.uncompleted.order("deadline DESC")
  tasks_uncompleted += executed_tasks.uncompleted.order("deadline DESC")
  tasks_uncompleted.sort_by { |h| h[:deadline] }.reverse!
end

tasks_controller:

@tasks = current_user.tasks_uncompleted.paginate(page: params[:page], per_page: 12)

方案二：

task.rb

scope :completed, -> { where.not(completed_at: nil) }
scope :uncompleted, -> { where(completed_at: nil) }
scope :alltasks, -> (u) { where('executor_id = ? OR assigner_id = ?', u.id, u.id) }

tasks_controller

@tasks = Task.alltasks(current_user).uncompleted.order("deadline DESC").paginate(page: params[:page], per_page: 12)

Answer 1

解决方案 2 是从数据库中检索记录的更有效方法。在大多数 Rails 应用程序中，对数据库的调用是瓶颈的常见原因，在解决方案 2 中，您调用数据库一次以检索所有记录，但在解决方案 1 中，您调用数据库两次以检索同样的信息。

就我个人而言，我也认为此解决方案更具可读性、易于测试和可维护性，因此解决方案 2 在许多方面都比速度更好！

Answer 2

您应该在用户上定义一个关联，该关联将 return 所有由 executor_id 或 assigner_id 关联的任务:

class User < ActiveRecord::Base
  has_many :assigned_and_executed_tasks,
           ->(user) { where('executor_id = ? OR assigner_id = ?', user, user) },
           class_name: 'Task',
           source: :tasks
end

user = User.find(123)
user.assigned_and_executed_tasks
# => SELECT tasks.* FROM tasks WHERE executor_id = 123 OR assigner_id = 123;

然后你可以像在 "Solution 2," 中那样做，但你可以只做 current_user.assigned_and_executed_tasks 而不是不幸的 Task.alltasks(current_user) （当然你可以给它一个更短的名字，但描述性名字比短的好):

@tasks = current_user.assigned_and_executed_tasks
           .uncompleted
           .order("deadline DESC")
           .paginate(page: params[:page], per_page: 12)

哪个 rails query/chain 更好？

which rails query/chain is better?

sql

activerecord

ruby-on-rails

chaining