Rails 5 - 使用具有关联模型查询的范围方法答案

【问题标题】：Rails 5 - Using scope method with associated models queryRails 5 - 使用具有关联模型查询的范围方法
【发布时间】：2017-08-10 17:39:54
【问题描述】：

我正在尝试创建一个范围方法，该方法仅查询最近更新过的记录（或其关联模型最近更新过）。我相信生成的 SQL 语句看起来不错，但是当应该有一些结果时我没有看到任何结果。感谢您的帮助！

控制器

class Api::V1::EncountersController < ApplicationController
  respond_to :json

  def index
    if params.has_key?(:datestart)
      ...
    elsif params.has_key?(:updated_since)
      date = Date.parse(params[:updated_since])
      respond_with(Encounter.by_updated_since(date),
                  :include => [:facility, :physician, :encounter_type, :group, :provider, :insurance],
                  :except => [:facility_id, :physician_id, :encounter_type_id, :group_id, :provider_id, :insurance_id])
    else
      ...
    end
  end

型号

    class Encounter < ApplicationRecord
      validates :encounter_type, :physician, :facility, :datetime_start_utc_scheduled, :procedures, :presence => true
      belongs_to :encounter_type
      belongs_to :physician
      belongs_to :facility
      belongs_to :insurance
      belongs_to :group, optional: true
      has_many :encounter_procedures, :dependent => :destroy
      has_many :procedures, through: :encounter_procedures
      has_many :actuals, :dependent => :destroy
      has_many :providers, through: :actuals

      ...

      scope :by_updated_since, -> updated_at {
        joins(:facility)
        .joins(:physician)
        .joins(:encounter_type)
        .joins(:group)
        .joins(:insurance)
        .where("encounters.updated_at >= ? OR
               facilities.updated_at >= ? OR
               physicians.updated_at >= ? OR
               encounter_types.updated_at >= ? OR
               groups.updated_at >= ? OR
               insurances.updated_at >= ?",
               updated_at, updated_at, updated_at, updated_at, updated_at, updated_at)}
   ...
   end

生成 SQL 的日志

app/controllers/api/v1/encounters_controller.rb:12:in `index'
Started GET "/api/v1/encounters?updated_since=2017-08-01" for 127.0.0.1 at 2017-08-10 11:55:01 -0500
Processing by Api::V1::EncountersController#index as JSON
  Parameters: {"updated_since"=>"2017-08-01"}
  Encounter Load (32.2ms)  SELECT "encounters".* FROM "encounters" INNER JOIN "facilities" ON "facilities"."id" = "encounters"."facility_id" INNER JOIN "physicians" ON "physicians"."id" = "encounters"."physician_id" INNER JOIN "encounter_types" ON "encounter_types"."id" = "encounters"."encounter_type_id" INNER JOIN "groups" ON "groups"."id" = "encounters"."group_id" INNER JOIN "insurances" ON "insurances"."id" = "encounters"."insurance_id" WHERE (encounters.updated_at >= '2017-08-01' OR
           facilities.updated_at >= '2017-08-01' OR
           physicians.updated_at >= '2017-08-01' OR
           encounter_types.updated_at >= '2017-08-01' OR
           groups.updated_at >= '2017-08-01' OR
           insurances.updated_at >= '2017-08-01')
[active_model_serializers] Rendered ActiveModel::Serializer::CollectionSerializer with ActiveModelSerializers::Adapter::Attributes (0.12ms)
Completed 200 OK in 81ms (Views: 31.4ms | ActiveRecord: 32.2ms)

【问题讨论】：

你正在做很多连接！也许你应该在你的belongs_to 关系中考虑touch: true (apidock.com/rails/ActiveRecord/Persistence/touch)
另外，这些连接关系是强制性的吗？例如，如果Encounter 记录没有（现有的）关联Insurance，则INNER JOIN 将从列表中删除该Encounter 记录。尝试使用includes 而不是joins
我认为它们是强制性的，因此如果关联模型最近更新（而不是 Encounter 记录本身），Encounter 记录仍会显示在结果中。
当我将“joins”更改为“includes”时出现错误--->“PG::UndefinedTable: ERROR: missing FROM-clause entry for table "facilities" LINE 2: facility.updated_at >= '2017-08-01' OR ^ : SELECT "encounters".* FROM "encounters" WHERE (encounters.updated_at >= '2017-08-01' OR facility.updated_at >= '2017-08-01' OR医师.updated_at >= '2017-08-01' 或遇到类型.updated_at >= '2017-08-01' 或 groups.updated_at >= '2017-08-01' 或 insurances.updated_at >= '2017-08-01 ')"
试试includes(:facility, :physician, :encounter_type, :group, :insurance).references(:facility, :physician, :encounter_type, :group, :insurance).where(...)

标签： ruby-on-rails scope rails-activerecord ruby-on-rails-5

【解决方案1】：

您的问题：

ActiveRecord joins 生成一个INNER JOIN，因此User.joins(:posts) 仅返回User 具有至少 1 个关联Post 的记录。

我很确定如果你做一个简单的Encounter.joins(:facility, :physician, :encounter_type, :group, :insurance) 它会返回一个空列表。

解决方案：

将includes 与references 结合使用，这样它就不会忽略没有关联记录的遇到记录：

Encounter.includes(:facility, :physician, :encounter_type, :group, :insurance).references(:facility, :physician, :encounter_type, :group, :insurance).where([...])

在你的范围内：

scope :by_updated_since, -> updated_at {
        includes(:facility, :physician, :encounter_type, :group, :insurance)
        .references(:facility, :physician, :encounter_type, :group, :insurance)
        .where("encounters.updated_at >= ? OR
               facilities.updated_at >= ? OR
               physicians.updated_at >= ? OR
               encounter_types.updated_at >= ? OR
               groups.updated_at >= ? OR
               insurances.updated_at >= ?",
               updated_at, updated_at, updated_at, updated_at, updated_at, updated_at)}

改进建议：

scope :by_updated_since, ->(updated_at) {
            relations = %i(facility physician encounter_type group insurance)
            sql_cond = relations.map(&:pluralize).map { |table_name| "#{table_name}.updated_at >= :datetime" }.join(' OR ')
            includes(*relations)
            .references(*relations)
            .where(sql_cond, datetime: updated_at) }

但我担心.references 需要一个 table_name 而不是关系名称...

【讨论】：