Hive之count (distinct)剖析与优化

HIVE —— count distinct优化方法

市场部小姐姐：我的sql为啥这么慢呀？
做去重统计时，小姐姐一般都这么写：

select
  count(distinct (bill_no)) as visit_users
from
  i_usoc_user_info_d
where
  p_day = '20200408'
  and bill_no is not null
  and bill_no