refactor(reference time): extract end_at from SQL

for performance efficiency while getting statistics

app/controllers/concerns/course/statistics/reference_times_concern.rb

@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+module Course::Statistics::ReferenceTimesConcern
+  private
+
+  def personal_end_at_hash
+    personal_end_at = Course::PersonalTime.find_by_sql(<<-SQL.squish
+      WITH course_user_personal_end_at AS (
+        SELECT course_user_id, end_at
+        FROM course_personal_times cpt
+        JOIN (
+          SELECT course_lesson_plan_items.id
+          FROM course_lesson_plan_items
+          WHERE course_lesson_plan_items.actable_type = 'Course::Assessment'
+            AND course_lesson_plan_items.actable_id = #{assessment_params[:id]}
+        ) clpi
+        ON cpt.lesson_plan_item_id = clpi.id
+      ),
+
+      personal_times AS (
+        SELECT cu.id AS course_user_id, pt.end_at
+        FROM (
+          SELECT course_users.id
+          FROM course_users
+          WHERE course_users.course_id = #{@assessment.course.id}
+        ) cu
+        LEFT JOIN (
+          SELECT course_user_id, end_at
+          FROM course_user_personal_end_at
+        ) pt
+        ON cu.id = pt.course_user_id
+      ),
+
+      personal_reference_times AS (
+        SELECT cu.id AS course_user_id, crt.end_at
+        FROM (
+          SELECT course_users.id, course_users.reference_timeline_id
+          FROM course_users
+          WHERE course_users.course_id = #{@assessment.course.id} AND course_users.role = #{CourseUser.roles[:student]}
+        ) cu
+        LEFT JOIN (
+          SELECT reference_timeline_id, lesson_plan_item_id, end_at
+          FROM course_reference_times
+        ) crt
+        ON crt.reference_timeline_id = cu.reference_timeline_id
+        LEFT JOIN (
+          SELECT id
+          FROM course_lesson_plan_items
+          WHERE course_lesson_plan_items.actable_type = 'Course::Assessment'
+            AND course_lesson_plan_items.actable_id = #{assessment_params[:id]}
+        ) clpi
+        ON crt.lesson_plan_item_id = clpi.id
+      )
+
+      SELECT
+        pt.course_user_id,
+        CASE WHEN pt.end_at IS NOT NULL THEN pt.end_at ELSE prt.end_at END AS end_at
+      FROM personal_times pt
+      LEFT JOIN personal_reference_times prt
+      ON pt.course_user_id = prt.course_user_id
+    SQL
+                                                      )
+    personal_end_at.map { |pea| [pea.course_user_id, pea.end_at] }.to_h
+  end
+
+  def reference_times_hash
+    reference_times = Course::ReferenceTime.find_by_sql(<<-SQL.squish
+      SELECT clpi.actable_id AS lesson_plan_item_id, crt.end_at
+      FROM course_reference_times crt
+      JOIN (
+        SELECT id
+        FROM course_reference_timelines
+        WHERE course_id = #{@assessment.course.id} AND "default" = TRUE
+      ) crtl
+      ON crt.reference_timeline_id = crtl.id
+      JOIN (
+        SELECT id, actable_id
+        FROM course_lesson_plan_items
+        WHERE course_lesson_plan_items.actable_type = 'Course::Assessment'
+          AND course_lesson_plan_items.actable_id = #{assessment_params[:id]}
+      ) clpi
+      ON crt.lesson_plan_item_id = clpi.id
+    SQL
+                                                       )
+    reference_times.map { |rt| [rt.lesson_plan_item_id, rt.end_at] }.to_h
+  end
+end

app/controllers/concerns/course/statistics/submissions_concern.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 module Course::Statistics::SubmissionsConcern
+  include Course::Statistics::ReferenceTimesConcern
+
   private
 
   def initialize_student_hash(students)
@@ -80,26 +82,34 @@ def answer_statistics_hash
 
   def populate_hash_including_answers(student_hash, submissions)
     answers_hash = answer_statistics_hash
+    fetch_personal_and_reference_timeline_hash
 
     submissions.map do |submission|
       submitter_course_user = submission.creator.course_users.select { |u| u.course_id == @assessment.course_id }.first
       next unless submitter_course_user&.student?
 
       answers = answers_hash[submission.id]
-      end_at = @assessment.lesson_plan_item.time_for(submitter_course_user).end_at
+      end_at = @personal_end_at_hash[submitter_course_user.id] || @reference_times_hash[@assessment.id]
 
       student_hash[submitter_course_user] = [submission, answers, end_at]
     end
   end
 
   def populate_hash_without_answers(student_hash, submissions)
+    fetch_personal_and_reference_timeline_hash
+
     submissions.map do |submission|
       submitter_course_user = submission.creator.course_users.select { |u| u.course_id == @assessment.course_id }.first
       next unless submitter_course_user&.student?
 
-      end_at = @assessment.lesson_plan_item.time_for(submitter_course_user).end_at
+      end_at = @personal_end_at_hash[submitter_course_user.id] || @reference_times_hash[@assessment.id]
 
       student_hash[submitter_course_user] = [submission, end_at]
     end
   end
+
+  def fetch_personal_and_reference_timeline_hash
+    @personal_end_at_hash = personal_end_at_hash
+    @reference_times_hash = reference_times_hash
+  end
 end

app/controllers/course/statistics/assessments_controller.rb

@@ -7,8 +7,7 @@ class Course::Statistics::AssessmentsController < Course::Statistics::Controller
   def main_statistics
     @assessment = Course::Assessment.where(id: assessment_params[:id]).
                   calculated(:maximum_grade, :question_count).
-                  preload(lesson_plan_item: [:reference_times, personal_times: :course_user],
-                          course: :course_users).first
+                  preload(course: :course_users).first
     submissions = Course::Assessment::Submission.where(assessment_id: assessment_params[:id]).
                   calculated(:grade, :grader_ids).
                   preload(creator: :course_users)