improve blueprint associations performance for many teachers

we try to return teacher information but having thousands
of teachers slows things down so just return a count
(like we do on the account course search)

test plan:
* have a course with more than 5 teachers
* should be able to search for and add them to a
blueprint course and have the UI show a count
instead of every teacher's name

closes #LA-863

Change-Id: Ie4d2294d04492e52d9f6854886458871c7f050d9
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/231920
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Jeremy Stanley <jeremy@instructure.com>
Product-Review: James Williams <jamesw@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>

app/controllers/master_courses/master_templates_controller.rb

@@ -279,6 +279,7 @@ class MasterCourses::MasterTemplatesController < ApplicationController
     courses = Api.paginate(scope, self, api_v1_course_blueprint_associated_courses_url)
     can_read_sis = @course.account.grants_any_right?(@current_user, :read_sis, :manage_sis)
 
+    preload_teachers(courses)
     json = courses.map do |course|
       course_summary_json(course, can_read_sis: can_read_sis, include_teachers: true)
     end

app/jsx/blueprint_courses/apiClient.js

@@ -54,6 +54,7 @@ const ApiClient = {
       {blueprint_associated: 'false'},
       {'include[]': 'term'},
       {'include[]': 'teachers'},
+      {teacher_limit: '5'},
       {search_term: search},
       {enrollment_term_id: term}
     ])
@@ -62,7 +63,7 @@ const ApiClient = {
   },
 
   getAssociations({masterCourse}) {
-    const params = this._queryString([{per_page: '100'}])
+    const params = this._queryString([{per_page: '100'}, {teacher_limit: '5'}])
 
     return this._depaginate(
       `/api/v1/courses/${masterCourse.id}/blueprint_templates/default/associated_courses?${params}`

app/jsx/blueprint_courses/components/AssociationsTable.js

@@ -176,7 +176,11 @@ export default class AssociationsTable extends React.Component {
           <td>{this.renderCellText(course.term.name)}</td>
           <td>{this.renderCellText(course.sis_course_id)}</td>
           <td>
-            {this.renderCellText(course.teachers.map(teacher => teacher.display_name).join(', '))}
+            {this.renderCellText(
+              course.teachers
+                ? course.teachers.map(teacher => teacher.display_name).join(', ')
+                : I18n.t('%{teacher_count} teachers', {teacher_count: course.teacher_count})
+            )}
           </td>
           <td className="bca-associations__x-col">
             <form
@@ -214,7 +218,11 @@ export default class AssociationsTable extends React.Component {
           <td>{this.renderCellText(course.term.name)}</td>
           <td>{this.renderCellText(course.sis_course_id)}</td>
           <td>
-            {this.renderCellText(course.teachers.map(teacher => teacher.display_name).join(', '))}
+            {this.renderCellText(
+              course.teachers
+                ? course.teachers.map(teacher => teacher.display_name).join(', ')
+                : I18n.t('%{teacher_count} teachers', {teacher_count: course.teacher_count})
+            )}
           </td>
           <td className="bca-associations__x-col">
             <form

app/jsx/blueprint_courses/components/CoursePickerTable.js

@@ -193,7 +193,11 @@ export default class CoursePickerTable extends React.Component {
         <td>{this.renderCellText(course.term.name)}</td>
         <td>{this.renderCellText(course.sis_course_id)}</td>
         <td>
-          {this.renderCellText(course.teachers.map(teacher => teacher.display_name).join(', '))}
+          {this.renderCellText(
+            course.teachers
+              ? course.teachers.map(teacher => teacher.display_name).join(', ')
+              : I18n.t('%{teacher_count} teachers', {teacher_count: course.teacher_count})
+          )}
         </td>
       </tr>
     ))

app/jsx/blueprint_courses/propTypes.js

@@ -45,7 +45,8 @@ propTypes.course = shape({
     shape({
       display_name: string.isRequired
     })
-  ).isRequired,
+  ),
+  teacher_count: string,
   sis_course_id: string
 })
 propTypes.courseList = arrayOf(propTypes.course)

lib/api/v1/course.rb

@@ -183,7 +183,7 @@ module Api::V1::Course
   def preload_teachers(courses)
     threshold = params[:teacher_limit].presence&.to_i
     if threshold
-      scope = TeacherEnrollment.active_or_pending.where(:course_id => courses).distinct.select(:user_id, :course_id)
+      scope = TeacherEnrollment.where.not(:workflow_state => %w{deleted rejected}).where(:course_id => courses).distinct.select(:user_id, :course_id)
       teacher_counts = Enrollment.from("(#{scope.to_sql}) AS t").group("t.course_id").count
       to_preload = []
       courses.each do |course|

lib/api/v1/master_courses.rb

@@ -99,7 +99,13 @@ module Api::V1::MasterCourses
     hash = api_json(course, @current_user, session, :only => %w{id name course_code})
     hash['sis_course_id'] = course.sis_source_id if can_read_sis
     hash['term_name'] = course.enrollment_term.name
-    hash['teachers'] = course.teachers.map { |teacher| user_display_json(teacher) } if opts[:include_teachers]
+    if opts[:include_teachers]
+      if course.teacher_count
+        hash['teacher_count'] = course.teacher_count
+      else
+        hash['teachers'] = course.teachers.map { |teacher| user_display_json(teacher) }
+      end
+    end
     hash
   end