discourse/lib/jobs/enqueue_digest_emails.rb

module Jobs

  # A daily job that will enqueue digest emails to be sent to users
  class EnqueueDigestEmails < Jobs::Base

    def execute(args)
      target_users.each do |u|
        Jobs.enqueue(:user_email, type: :digest, user_id: u.id)
      end      
    end

    def target_users
      # Users who want to receive emails and haven't been emailed int he last day
      User
        .select(:id)        
        .where(email_digests: true)
        .where("COALESCE(last_emailed_at, '2010-01-01') <= CURRENT_TIMESTAMP - ('1 DAY'::INTERVAL * digest_after_days)")
        .where("COALESCE(last_seen_at, '2010-01-01') <= CURRENT_TIMESTAMP - ('1 DAY'::INTERVAL * digest_after_days)")
    end

  end

end