arrays - 如何按位置对 postgresql 数组的元素求和？

Question

假设我有一个返回生产作业表的查询，并且在一列中我有过去 7 天每个作业的输出数组:

 sku | job | outputs
-----------------------------
 A1  | 123 | {2,4,6,5,5,5,5}
 A1  | 135 | {0,0,0,3,5,7,9}
 B3  | 109 | {3,2,3,2,3,2,3}
 C5  | 144 | {5,5,5,5,5,5,5}

如何编写一个按 SKU(产品编号)分组并按位置对 7 天输出求和的查询？在这种情况下，您可以看到产品 A1 有两个生产作业:它们应该合并到结果的一行中:

 sku | outputs
--------------------------
 A1  | {2,4,6,8,10,12,14}
 B3  | {3,2,3,2,3,2,3}
 C5  | {5,5,5,5,5,5,5}

Answer 1

您应该使用序数取消嵌套数组，按 sku 和序数计算分组中元素的总和，最后使用按 sku 分组的序数将总和聚合到数组中:

select sku, array_agg(elem order by ordinality) as outputs
from (
    select sku, ordinality, sum(elem) as elem
    from jobs
    cross join unnest(outputs) with ordinality as u(elem, ordinality)
    group by 1, 2
    ) s
group by 1
order by 1

DbFiddle.

如果您在各种情况下经常需要此功能，创建自定义聚合可能是合理的:

create or replace function sum_int_arrays(int[], int[])
returns int[] language sql immutable as $$
    select array_agg(coalesce(a, 0)+ b)
    from unnest($1, $2) as u(a, b)
$$;

create aggregate sum_int_array_agg(integer[]) (
    sfunc = sum_int_arrays,
    stype = int[]
);

select sku, sum_int_array_agg(outputs)
from jobs
group by 1
order by 1

DbFiddle.