从丑陋的方式开始:您可以将数学压平到查询中。也就是转for i in ... sum(min(...)/abs(...))
进入对每个字段进行操作的 SQL。注意MIN
and SUM
是您不想使用的聚合函数。而是使用+
对于总和和IF(a < b, a, b)
for MIN
. ABS(a, b)
好像IF(a < b, b-a, a-b)
。如果你只是计算欧几里德距离,你可以这样做
SELECT left.user, right.user,
SQRT((left.x-right.x)*(left.x-right.x)
+ (left.y-right.y)*(left.y-right.y)
+ (left.z-right.z)*(left.z-right.z)) as dist
FROM (
SELECT *
FROM dataset.table1 AS left
CROSS JOIN dataset.table1 AS right)
更好的方法是用户定义函数,并将向量创建为重复值。然后你可以写一个DISTANCE()
对交叉连接左侧和右侧的两个数组执行计算的函数。如果您尚未加入 UDF Beta 计划并想加入,请联系 Google Cloud 支持。
最后,如果您更改架构{user:string, field1:float, field2:float, field3:float,...}
to {user:string, fields:[field:float]}
然后,您可以使用位置展平该字段并对其进行交叉连接。如:
SELECT
user,
field,
index,
FROM (FLATTEN((
SELECT
user,
fields.field as field,
POSITION(fields.field) as index,
from [dataset1.table1]
), fields))
如果将其另存为视图,请将其命名为“dataset1.flat_view”
然后你就可以加入:
SELECT left.user as user1, right.user as user2,
left.field as l, right.field as r,
FROM dataset1.flat_view left
JOIN dataset1.flat_view right
ON left.index = right.index
WHERE left.user != right.user
这将为每对用户和每个字段匹配字段提供一行。您可以将其保存为视图“dataset1.joined_view”。
最后,您可以进行聚合:
既然你想要这个:
sum(min(user1_row[i], user2_row[i]) / abs(user1_row[i] - user2_row[i]))
它看起来像:
SELECT user1, user2,
SUM((if (l < r, l, r)) / (if (l > r, l-r, r-l))
FROM [dataset1.joined_view]
GROUP EACH BY user1, user2