调整

app/jobs/create_subject_course_student_job.rb

@@ -12,9 +12,8 @@ class CreateSubjectCourseStudentJob < ApplicationJob
       course.subject.subject_appointments.each do |app|
         next if course.students.where(user_id: app.user_id).any?
         worker.add same_attrs.merge(user_id: app.user_id)
+        app.destroy
       end
     end
-
-    course.subject.subject_appointments.destroy_all
   end
 end