Question

我有一个配置单元表

operator []

这是一条记录的样子

create table mySource(
    col_1   map<string, string>,
    col_2   map<string, string>
)

我的目标表如下

col_1                col_2
{"a":1, "b":"2"}     {"c":3, "d":"4"}

现在，我想将mySource中的两列合并为一个映射，并将其提供给目标表。基本上我想写类似的东西

create table myTarget(
        my_col   map<string, string>
    )

蜂巢中是否有内置方法可以做到这一点？我用collect_set尝试了几件事，但是出现了很多错误

Answer 1

仅使用内置方法的解决方案。展开两个地图，将所有结果都合并，收集key:value的数组，将数组与','连接，使用str_to_map将字符串转换为地图：

with mytable as (--Use your table instead of this
select 
map('a','1', 'b','2') as col_1, map('c','3', 'd','4') as col_2
)

select str_to_map(concat_ws(',',collect_set(concat(key,':',val)))) as mymap
from
(
select m1.key, m1.val 
  from mytable
       lateral view explode(col_1) m1 as key, val
union all
select m2.key, m2.val 
  from mytable
       lateral view explode(col_2) m2 as key, val
)s       
;

结果：

mymap

{"a":"1","b":"2","c":"3","d":"4"}

有了brickhouse库，会容易得多：

ADD JAR /path/to/jar/brickhouse-0.7.1.jar;
CREATE TEMPORARY FUNCTION COMBINE AS 'brickhouse.udf.collect.CombineUDF';

select combine(col_1, col_2) as mymap from mytable;

蜂巢：将两张地图合并为一列

1 个答案: