Rails ERROR: 'missing FROM-clause entry' when order through associated model

Question

在我的 Rails 5 和 Ruby 2.4 应用程序中，我有两个模型 CaregiverAuthorization 和 Registrant:

# caregiver_authorization
class CaregiverAuthorization < ApplicationRecord
  belongs_to :registrant

  scope :pending, (-> { where(status: [statuses[:pending], statuses[:pending_renewal]]) })
end

# registrant
class Registrant < User
  has_many :caregiver_authorizations,
           (-> { order('created_at asc') })

  def full_name
    [first_name, last_name].join(' ')
  end
end

现在我想让 registrant.full_name 订购所有待处理的 caregiver_authorizations。很简单，所以我做到了：

CaregiverAuthorization.includes(:registrant).order("registrants.full_name")

令人惊讶的是我得到了以下错误：

ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "registrants"
LINE 1: ...id" AND "users"."type" IN ('Registrant') ORDER BY registrant...
                                                             ^

我错过了什么？

[编辑]

完整错误信息：

  SQL (0.8ms)  SELECT "caregiver_authorizations"."id" AS t0_r0, "caregiver_authorizations"."registrant_id" AS t0_r1, "caregiver_authorizations"."reviewer_id" AS t0_r2, "caregiver_authorizations"."reviewed_at" AS t0_r3, "caregiver_authorizations"."status" AS t0_r4, "caregiver_authorizations"."created_at" AS t0_r5, "caregiver_authorizations"."updated_at" AS t0_r6, "users"."id" AS t1_r0, "users"."external_system_id" AS t1_r1, "users"."external_system_type" AS t1_r2, "users"."type" AS t1_r3, "users"."login_id" AS t1_r4, "users"."first_name" AS t1_r5, "users"."last_name" AS t1_r6, "users"."status" AS t1_r7, "users"."minor" AS t1_r8, "users"."created_at" AS t1_r9, "users"."updated_at" AS t1_r10, "users"."paper_entry" AS t1_r11, "users"."date_of_birth" AS t1_r12, "users"."caregiver_limit_override" AS t1_r13, "users"."patient_limit_override" AS t1_r14 FROM "caregiver_authorizations" LEFT OUTER JOIN "users" ON "users"."id" = "caregiver_authorizations"."registrant_id" AND "users"."type" IN ('Registrant') ORDER BY registrants.full_name
ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "registrants"
LINE 1: ...id" AND "users"."type" IN ('Registrant') ORDER BY registrant...
                                                             ^
: SELECT "caregiver_authorizations"."id" AS t0_r0, "caregiver_authorizations"."registrant_id" AS t0_r1, "caregiver_authorizations"."reviewer_id" AS t0_r2, "caregiver_authorizations"."reviewed_at" AS t0_r3, "caregiver_authorizations"."status" AS t0_r4, "caregiver_authorizations"."created_at" AS t0_r5, "caregiver_authorizations"."updated_at" AS t0_r6, "users"."id" AS t1_r0, "users"."external_system_id" AS t1_r1, "users"."external_system_type" AS t1_r2, "users"."type" AS t1_r3, "users"."login_id" AS t1_r4, "users"."first_name" AS t1_r5, "users"."last_name" AS t1_r6, "users"."status" AS t1_r7, "users"."minor" AS t1_r8, "users"."created_at" AS t1_r9, "users"."updated_at" AS t1_r10, "users"."paper_entry" AS t1_r11, "users"."date_of_birth" AS t1_r12, "users"."caregiver_limit_override" AS t1_r13, "users"."patient_limit_override" AS t1_r14 FROM "caregiver_authorizations" LEFT OUTER JOIN "users" ON "users"."id" = "caregiver_authorizations"."registrant_id" AND "users"."type" IN ('Registrant') ORDER BY registrants.full_name

也许这会有所帮助：

2.4.5 :065 > CaregiverAuthorization.includes(:registrant).order("registrants.full_name").to_sql
 => "SELECT \"caregiver_authorizations\".\"id\" AS t0_r0, \"caregiver_authorizations\".\"registrant_id\" AS t0_r1, \"caregiver_authorizations\".\"reviewer_id\" AS t0_r2, \"caregiver_authorizations\".\"reviewed_at\" AS t0_r3, \"caregiver_authorizations\".\"status\" AS t0_r4, \"caregiver_authorizations\".\"created_at\" AS t0_r5, \"caregiver_authorizations\".\"updated_at\" AS t0_r6, \"users\".\"id\" AS t1_r0, \"users\".\"external_system_id\" AS t1_r1, \"users\".\"external_system_type\" AS t1_r2, \"users\".\"type\" AS t1_r3, \"users\".\"login_id\" AS t1_r4, \"users\".\"first_name\" AS t1_r5, \"users\".\"last_name\" AS t1_r6, \"users\".\"status\" AS t1_r7, \"users\".\"minor\" AS t1_r8, \"users\".\"created_at\" AS t1_r9, \"users\".\"updated_at\" AS t1_r10, \"users\".\"paper_entry\" AS t1_r11, \"users\".\"date_of_birth\" AS t1_r12, \"users\".\"caregiver_limit_override\" AS t1_r13, \"users\".\"patient_limit_override\" AS t1_r14 FROM \"caregiver_authorizations\" LEFT OUTER JOIN \"users\" ON \"users\".\"id\" = \"caregiver_authorizations\".\"registrant_id\" AND \"users\".\"type\" IN ('Registrant') ORDER BY registrants.full_name"

Answer 1

请注意 includes 不一定要在数据库查询中加入 table。它是为了避免 N+1 查询而构建的，它可能只是运行两个查询（一个用于 caregiver_authorizations，另一个用于关联的 registrants.

当您在一个查询中确实需要两个 table 时，因为您需要按它们进行过滤或排序，那么您需要使用 joins。此外，table 没有命名为 registrants，而是命名为 users，因为 Registrant 是 User 的子类。而且您不能按 full_name 排序，因为 full_name 不是数据库查询，而是模型中的一种方法。要按 full_name 排序，您需要在 SQL.

中模拟该方法的行为

我想以下内容应该适合您：

CaregiverAuthorization
  .pending
  .joins(:registrant)
  .order(Arel.sql("LOWER(CONCAT(users.first_name, ' ', users.last_name))"))

Rails ERROR: 'missing FROM-clause entry' when order through associated model

Rails ERROR: 'missing FROM-clause entry' when order through associated model

ruby

ruby-on-rails