perf: reduce number of queries for respondents

app/models/report/subcategory.rb

@@ -1,10 +1,10 @@
 module Report
   class Subcategory
-    def self.create_report(schools: School.all.includes(:district), academic_years: AcademicYear.all, subcategories: ::Subcategory.all, filename: 'subcategories.csv')
+    def self.create_report(schools: School.all.includes(:district), academic_years: AcademicYear.all, subcategories: ::Subcategory.all, filename: "subcategories.csv")
       data = []
       mutex = Thread::Mutex.new
-      data << ['District', 'School', 'School Code', 'Academic Year', 'Recorded Date Range', 'Grades', 'Subcategory', 'Student Score', 'Student Zone', 'Teacher Score',
-               'Teacher Zone', 'Admin Score', 'Admin Zone', 'All Score (Average)', 'All Score Zone']
+      data << ["District", "School", "School Code", "Academic Year", "Recorded Date Range", "Grades", "Subcategory", "Student Score", "Student Zone", "Teacher Score",
+               "Teacher Zone", "Admin Score", "Admin Zone", "All Score (Average)", "All Score Zone"]
       pool_size = 2
       jobs = Queue.new
       schools.each { |school| jobs << school }
@@ -14,7 +14,7 @@ module Report
           while school = jobs.pop(true)
             academic_years.each do |academic_year|
               subcategories.each do |subcategory|
-                respondents = Respondent.find_by(school:, academic_year:)
+                respondents = Respondent.by_school_and_year(school:, academic_year:)
                 next if respondents.nil?
 
                 response_rate = subcategory.response_rate(school:, academic_year:)
@@ -58,8 +58,8 @@ module Report
       end
 
       workers.each(&:join)
-      FileUtils.mkdir_p Rails.root.join('tmp', 'reports')
-      filepath = Rails.root.join('tmp', 'reports', filename)
+      FileUtils.mkdir_p Rails.root.join("tmp", "reports")
+      filepath = Rails.root.join("tmp", "reports", filename)
       write_csv(data:, filepath:)
       data
     end
@@ -76,7 +76,7 @@ module Report
     def self.student_score(row:)
       row in [response_rate, subcategory, school, academic_year]
       student_score = subcategory.student_score(school:, academic_year:) if response_rate.meets_student_threshold?
-      student_score || 'N/A'
+      student_score || "N/A"
     end
 
     def self.student_zone(row:)
@@ -86,14 +86,14 @@ module Report
                                                 academic_year:).type.to_s.capitalize
       end
 
-      student_zone || 'N/A'
+      student_zone || "N/A"
     end
 
     def self.teacher_score(row:)
       row in [response_rate, subcategory, school, academic_year]
       teacher_score = subcategory.teacher_score(school:, academic_year:) if response_rate.meets_teacher_threshold?
 
-      teacher_score || 'N/A'
+      teacher_score || "N/A"
     end
 
     def self.teacher_zone(row:)
@@ -102,20 +102,20 @@ module Report
         teacher_zone = subcategory.teacher_zone(school:, academic_year:).type.to_s.capitalize
       end
 
-      teacher_zone || 'N/A'
+      teacher_zone || "N/A"
     end
 
     def self.admin_score(row:)
       row in [response_rate, subcategory, school, academic_year]
       admin_score = subcategory.admin_score(school:, academic_year:)
-      admin_score = 'N/A' unless admin_score >= 0
+      admin_score = "N/A" unless admin_score >= 0
       admin_score
     end
 
     def self.admin_zone(row:)
       row in [response_rate, subcategory, school, academic_year]
       tmp_zone = subcategory.admin_zone(school:, academic_year:).type
-      tmp_zone == :insufficient_data ? 'N/A' : tmp_zone.to_s.capitalize
+      tmp_zone == :insufficient_data ? "N/A" : tmp_zone.to_s.capitalize
     end
   end
 end

app/models/respondent.rb

@@ -16,4 +16,12 @@ class Respondent < ApplicationRecord
       end
     end
   end
+
+  def self.by_school_and_year(school:, academic_year:)
+    @by_school_and_year ||= Hash.new do |memo, (school, academic_year)|
+      memo[[school, academic_year]] = Respondent.find_by(school:, academic_year:)
+    end
+
+    @by_school_and_year[[school, academic_year]]
+  end
 end

app/models/response_rate_calculator.rb

@@ -40,7 +40,7 @@ class ResponseRateCalculator
   end
 
   def respondents
-    @respondents ||= Respondent.find_by(school:, academic_year:)
+    @respondents ||= Respondent.by_school_and_year(school:, academic_year:)
   end
 
   def population_data_unavailable?

app/models/school.rb

@@ -21,6 +21,6 @@ class School < ApplicationRecord
   end
 
   def grades(academic_year:)
-    @grades ||= Respondent.find_by(school: self, academic_year:)&.enrollment_by_grade&.keys || (-1..12).to_a
+    @grades ||= Respondent.by_school_and_year(school: self, academic_year:)&.enrollment_by_grade&.keys || (-1..12).to_a
   end
 end

app/presenters/analyze/graph/column/grouped_bar_column_presenter.rb

@@ -142,7 +142,7 @@ module Analyze
         end
 
         def grades(year_index)
-          Respondent.find_by(school:, academic_year: academic_years[year_index]).enrollment_by_grade.keys
+          Respondent.by_school_and_year(school:, academic_year: academic_years[year_index]).enrollment_by_grade.keys
         end
 
         private

app/presenters/response_rate_presenter.rb

@@ -99,7 +99,7 @@ class ResponseRatePresenter
   end
 
   def respondents
-    Respondent.find_by(school:, academic_year:)
+    @respondents ||= Respondent.by_school_and_year(school:, academic_year:)
   end
 
   def grades