Modify subcategory report to be threaded

app/models/report/subcategory.rb

@@ -1,10 +1,17 @@
 module Report
   class Subcategory
-    def self.create_report(schools: School.all, 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', 'Grades', 'Subcategory', 'Student Score', 'Student Zone', 'Teacher Score',
                'Teacher Zone', 'Admin Score', 'Admin Zone', 'All Score (Average)', 'All Score Zone']
-      schools.each do |school|
+      pool_size = 2
+      jobs = Queue.new
+      schools.each { |school| jobs << school }
+
+      workers = pool_size.times.map do
+        Thread.new do
+          while school = jobs.pop(true)
             academic_years.each do |academic_year|
               subcategories.each do |subcategory|
                 respondents = Respondent.find_by(school:, academic_year:)
@@ -20,6 +27,7 @@ module Report
 
                 all_grades = respondents.counts_by_grade.keys
                 grades = "#{all_grades.first}-#{all_grades.last}"
+                mutex.synchronize do
                   data << [school.district.name,
                            school.name,
                            school.dese_id,
@@ -37,7 +45,12 @@ module Report
                 end
               end
             end
+          end
+        rescue ThreadError
+        end
+      end
 
+      workers.each(&:join)
       FileUtils.mkdir_p Rails.root.join('tmp', 'reports')
       filepath = Rails.root.join('tmp', 'reports', filename)
       write_csv(data:, filepath:)