PostgreSQL查詢性能和變化

Question

我有一個事件表格，具有以下列user_id,points,created。我需要的是獲得給定月份的所有積分，給定的user_id總積分和總排名。我需要做的是在這導致了以下嘗試一個查詢：

select 
    e.user_id, 
    sum(e.points) as total_points, 
    (select sum(points) from event where user_id = 1 and extract(month from created) = 1) as month_points, 
    (select rank from (select user_id as id, rank() over (order by sum(points) desc) from event group by user_id) as rank where id = 1) 
from 
    event pte 
where 
    e.user_id = 1 
group by 
    e.user_id 
; 

我想什麼要問的是：

1. 此查詢可能會很慢？
2. 它可以做得更好/以另一種方式？
3. 是rank功能足夠可靠還是被誤用？

Answer 1

假設PostgreSQL的版本大於或等於9.4，你可以使用集合filter條款，以避免子查詢的month_points和rank：

select * from 
    (select 
     e.user_id, 
     sum(e.points) as total_points, 
     sum(points) filter (where extract(month from created) = 1) as month_points, 
     rank() over (order by sum(points) desc) 
    from 
     event e 
    group by 
     e.user_id 
    ) as inner_query 
where user_id = 1;