destroy_duplicates.rb

namespace :resource do
  desc 'remove duplicate saved students'
  task cleanup: :environment do
    # find all models and group them on keys which should be common
    grouped_by_foreign_keys = SavedStudent.all.group_by do |model|
      [model.recruiter_user_id, model.student_profile_id]
    end
    # grouped_by_email = Person.all.group_by{|model| [model.email] }
    # grouped_by_foreign_keys.merge(grouped_by_email).values.each do |duplicates|
    grouped_by_foreign_keys.values.each do |duplicates|
      # duplicates.shift # -> keep the first one
      duplicates.pop # -> keep the last one
      # if there are any more left, they are duplicates
      # so delete all of them
      duplicates.each(&:destroy) # duplicates can now be destroyed
    end
  end
end