ruby - 有没有更简洁的方法来检查 PGResult 是否为空？

Question

我正在使用 pg gem 从 Ruby 与 PostgreSQL 对话。有没有检查是否没有结果比使用 res.ntuples == 0 更好的方法？

conn = PGconn.connect config

cmd = "select * from labels inner join labels_mail using(label_id) " + 
  "where labels_mail.mail_id = $1 and labels.name = $2"

res = conn.exec(cmd, [mail_id, mailbox])

if res.ntuples == 0  #  <=== is there a better way to check this?
  cmd = "insert into labels_mail (mail_id, label_id) values ($1, $2)"
  conn.exec(cmd, [mail_id, label_id(mailbox)])
end

Answer 1

元组，打字错误？使用 zero? 比 == 0

更快更简洁

if res.num_tuples.zero?