优化“ COUNT（DISTINCT col）WHERE othercol =？”为了速度

Question

我有一个独特的计数，大约需要半分钟或更长时间才能得到结果。

select COUNT(DISTINCT ip) as unique_visits
from idevaff_iptracking
where acct_id = ? and stamp = ?

计算IP的更快方法是什么？ ip列和带有ip列的acct_id上都有索引。

Answer 1

对于此查询：

select COUNT(DISTINCT ip) as unique_visits
from idevaff_iptracking
where acct_id = ? and stamp = ?

您要在idevaff_iptracking(acct_d, stamp, ip)上建立索引。