discourse/app/jobs/scheduled/clean_up_inactive_users.rb

module Jobs

  class CleanUpInactiveUsers < Jobs::Scheduled
    every 1.day

    def execute(args)
      return if SiteSetting.clean_up_inactive_users_after_days <= 0

      User.joins("LEFT JOIN posts ON posts.user_id = users.id")
        .where(last_posted_at: nil, trust_level: TrustLevel.levels[:newuser], admin: false)
        .where(
          "posts.user_id IS NULL AND users.last_seen_at < ?",
          SiteSetting.clean_up_inactive_users_after_days.days.ago
      )
        .limit(1000)
        .pluck(:id).each_slice(50) do |slice|
        destroy(slice)
      end

    end

    private

    def destroy(ids)

      destroyer = UserDestroyer.new(Discourse.system_user)

      User.transaction do
        ids.each do |id|
          begin
            user = User.find(id)
            destroyer.destroy(user, transaction: false, context: I18n.t("user.destroy_reasons.inactive_user"))
          rescue => e
            Discourse.handle_job_exception(e,
             message: "Cleaning up inactive users",
             extra: { user_id: id }
            )
            raise e
          end
        end
      end
    end
  end
end