如何从基于多个分组的表中获取第一行

Question

我有一个PostgreSQL表，需要根据不同的列组（每个时间组由不同列的组合）选择第一条记录。

table1 (id1, id2, id3, id4, u1, u2, u3, ...)

我尝试了这段代码，它工作正常。

select 
  t.*,
  row_number() over (partition by id1, id2) as rn1,
  row_number() over (partition by id1, id3) as rn2,
  row_number() over (partition by id1, id2, id4) as rn3
from table1 t

我只需要每组的第一条记录（rn1 = 1，rn2 = 1，rn3 = 1）。

case when rn1 = 1 and u1 > 0 then 1 else 0 as res1
case when rn2 = 1 and u2 = 1 then 1 else 0 as res2
case when rn3 = 1 and u3 < 0 then 1 else 0 as res3

但是此查询非常慢，需要在不使用任何窗口函数的情况下将其重写。反正有做吗？