Hive：将两个地图合并为一列

Question

我有一个蜂巢 table 作为

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

这是记录的样子

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

我的目标 table 看起来像这样

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

现在我想将 mySource 中的两列组合成一个地图并将其提供给我的目标 table。基本上我想写一些像

insert into myTarget
    select
        some_method(col_1, col_2) as my_col
    from mySource;

hive 中是否有可以执行此操作的内置方法？我用 collect_set 尝试了一些东西，但出现了很多错误

Answer 1

仅使用内置方法的解决方案。分解两个映射，UNION ALL 结果，收集 key:value 的数组，将数组与 ',' 连接，使用 str_to_map:

将字符串转换为映射

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"}

使用 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;

Hive：将两个地图合并为一列

Hive : Merge two maps into one column

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