教师列表的性能优化

app/controllers/courses_controller.rb

@@ -284,6 +284,7 @@ class CoursesController < ApplicationController
     page = params[:page] || 1
     limit = params[:limit] || 20
     @teacher_list = @teacher_list.page(page).per(limit)
+    @teacher_list = @teacher_list.preload(:graduation_group, :user, :teacher_course_groups)
   end
 
   def apply_teachers

app/views/courses/teachers.json.jbuilder

@@ -7,9 +7,11 @@ json.teacher_list do
     json.user_id teacher.user.id
     json.role teacher.role == "CREATOR" ? "管理员" : teacher.role == "PROFESSOR" ? "教师" : "助教"
     json.course_groups do
-      json.array! CourseGroup.where(id: TeacherCourseGroup.where(course_member_id: teacher.id, user_id: teacher.user.id, course_id: @course.id).pluck(:course_group_id)) do |course_group|
-        json.name course_group.name
-        json.id course_group.id
+      if @course.course_groups_count > 0
+        json.array! @course.course_groups.select{|group| teacher.teacher_course_groups.pluck(:course_group_id).include?(group.id)} do |course_group|
+          json.name course_group.name
+          json.id course_group.id
+        end
       end
     end
     json.graduation_group teacher.graduation_group.try(:name)