在 bigquery 中装袋元素的桶数最少

如何解决在 bigquery 中装袋元素的桶数最少

我有一个带有桶和元素的矩阵，如下所示。如果一个元素可以放入一个桶中，那么它在相应的单元格中为 1

例如：如果您查看图像，元素 x 可以放入桶 a、b、c 而不是 d 和 e

我想找到最少的桶来分组我的元素。在这种情况下，桶 c 和 d 可以将所有元素分组到两个桶中。

知道我是否可以在 bigquery 中动态有效地执行此操作吗？原始数据没有这么简单。

 select "element-x" as element,1 as bucketa,1 as bucketb,1 as bucketc,0 as bucketd,0 as buckete
 union all
 select "element-y" as element,0 as bucketa,0 as bucketb,0 as buckete
 union all
 select "element-z" as element,0 as buckete
 union all
 select "element-p" as element,0 as buckete
 union all
 select "element-q" as element,0 as bucketc,1 as bucketd,0 as buckete
 union all
 select "element-r" as element,1 as buckete

解决方法

考虑以下解决方案 - 显然您需要确保在 matrix CTE 中提供准确的数据，并且您还需要分别调整 buckets_elements CTE 以反映矩阵中的所有桶。 CTE 的其余部分和最终查询将为您提供帮助！

with matrix as (
  select "element-x" as element,1 as bucketa,1 as bucketb,1 as bucketc,0 as bucketd,0 as buckete union all
  select "element-y",1,0 union all
  select "element-z",0 union all
  select "element-p",0 union all
  select "element-q",0 union all
  select "element-r",1    
),buckets_elements as ( 
  select array[struct(a),struct(b),struct(c),struct(d),struct(e)] buckets
  from (
    select 
      array_agg(if(bucketa = 1,element,null) ignore nulls) a,array_agg(if(bucketb = 1,null) ignore nulls) b,array_agg(if(bucketc = 1,null) ignore nulls) c,array_agg(if(bucketd = 1,null) ignore nulls) d,array_agg(if(buckete = 1,null) ignore nulls) e
    from matrix
  )
),columns_names as (
  select 
    regexp_extract_all(to_json_string((select as struct * except(element) from unnest([t]))),r'"([^"]+)"') cols
  from matrix t limit 1
),columns_index as (
  select generate_array(0,array_length(cols) - 1) as arr  
  from columns_names
),buckets_combinations as (
  select  
    (select array_agg(
      case when n & (1<<pos) <> 0 then arr[offset(pos)] end 
      ignore nulls)
     from unnest(generate_array(0,array_length(arr) - 1)) pos
    ) as combo
  from columns_index cross join 
  unnest(generate_array(1,cast(power(2,array_length(arr)) - 1 as int64))) n
)
select 
  array(select cols[offset(i)] from columns_names,unnest(combo) i) winners
from (
  select combo,rank() over(order by (select count(distinct  el) from unnest(val) v,unnest(v.a) el) desc,array_length(combo)) as rnk
  from (
    select any_value(c).combo,array_agg(buckets[offset(i)]) val
    from buckets_combinations c,unnest(combo) i,buckets_elements b
    group by format('%t',c)
  )
)
where rnk = 1

带输出