Rails 4 ActiveRecord帮助使用包括查询Postgres

时间：2015-09-17 17:30:08

标签： ruby-on-rails ruby postgresql activerecord

我们正试图加载与AR包含查询的关联，但我们遇到了一个问题。

控制器中的相关位：

def index
  @students = current_admin.current_cohort.students.includes(:attendance_records)
end

该部分似乎与生成的查询一起正常工作：

  Student Load (0.5ms)  SELECT "users".* FROM "users" WHERE "users"."type" IN ('Student') AND "users"."id" IN (413, 400, 386, 399, 380, 410)  ORDER BY "users"."name" ASC
  Student Load (0.8ms)  SELECT "users".* FROM "users" WHERE "users"."type" IN ('Student') AND "users"."cohort_id" = $1  ORDER BY "users"."name" ASC  [["cohort_id", 8]]
  AttendanceRecord Load (4.2ms)  SELECT "attendance_records".* FROM "attendance_records" WHERE "attendance_records"."student_id" IN (212, 216, 210, 282, 305, 283, 361, 265, 168, 229, 228, 376, 338, 223, 339, 308, 214, 185, 165, 224, 211, 91, 172, 221, 266, 220, 192, 240, 173, 226, 218, 302, 183, 241, 163, 219, 243, 231, 272, 244, 362, 213, 328, 171, 227, 202, 201, 275, 248, 236, 342, 217, 293, 194, 208, 39, 199, 170, 284)

问题是我们正在检查视图中其他位置的出勤记录，如下所示。这部分内容是查询数据库的出勤记录，即使它们已经预加载，导致n + 1查询问题。

查看代码：

<% if student.signed_in_today? %>
  <p class="text-success"><span class="check">&#x2713;</span> Signed in</p>
    <% if student.signed_out_today? %>
      <p class="text-success"><span class="check">&#x2713;</span> Signed out</p>
    <% else %>
      <%= form_for student.attendance_records.today.first do |f| %>
        <%= f.hidden_field :student_id, value: student.id %>
        <%= f.hidden_field :signing_out, value: true %>
        <%= f.submit "I'm leaving", class: 'btn btn-warning' %>
      <% end %>
    <% end %>
<% else %>
  <%= form_for AttendanceRecord.new do |f| %>
    <%= f.hidden_field :student_id, value: student.id %>
    <%= f.submit "I'm soloing", class: 'btn btn-primary' %>
  <% end %>
<% end %>

型号代码：

# Student model
  def signed_in_today?
    attendance_records.today.exists?
  end

  def signed_out_today?
    if signed_in_today?
      attendance_records.today.first.signed_out_time != nil
    end
  end

# AttendanceRecord model
    scope :today, -> { where(date: Time.zone.now.to_date) }

有问题的查询如下：

  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 212], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 216], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 210], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 282], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 305], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 283], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 361], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 265], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 168], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 229], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 228], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 376], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 338], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 223], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 339], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 308], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 214], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 185], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 165], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 224], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 211], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 91], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 172], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 221], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 266], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 220], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 192], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 240], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.3ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 173], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 226], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 218], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 302], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 183], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 241], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 163], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 219], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 243], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 231], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 272], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 244], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 362], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 213], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 328], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 171], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 227], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 202], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 201], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 275], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 248], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 236], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 342], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.2ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 217], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 293], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 194], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 208], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.3ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 39], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 199], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 170], ["date", "2015-09-17"]]
  AttendanceRecord Exists (0.1ms)  SELECT  1 AS one FROM "attendance_records" WHERE "attendance_records"."student_id" = $1 AND "attendance_records"."date" = $2 LIMIT 1  [["student_id", 284], ["date", "2015-09-17"]]

非常感谢任何帮助。谢谢！

1 个答案:

答案 0 :(得分：0)

只要您拨打where（就像在今天的范围内一样），您就会触发查询。您正在使用学生索引查询获取所需的记录 - 它们都将在内存中，因此您应将其视为数组 - 使用select之类的数组方法来查找所需的记录。

相关问题
最新问题