在Hive中爆炸一行XML数据

Question

我们将XML数据作为名为XML的单个字符串列加载到Hadoop中.我们试图检索到数据级别进行规范化或将其分解为单行进行处理(你知道,就像一个表!)尝试过爆炸功能,但没有得到我们想要的.

示例XML

<Reports>
<Report ID="1">
<Locations>
  <Location ID="20001">
    <LocationName>Irvine Animal Shelter</LocationName>
  </Location>   
  <Location ID="20002">
    <LocationName>Irvine City Hall</LocationName>
  </Location>   
  </Locations>
</Report>
<Report ID="2">
<Locations>
  <Location ID="10001">
    <LocationName>California Fish Grill</LocationName>
  </Location>   
  <Location ID="10002">
    <LocationName>Fukada</LocationName>
  </Location>   
  </Locations>
</Report>
</Reports>

查询1

我们正在查询更高级别的Report.Id,然后是孩子的ID和名称(位置/位置).以下基本上给出了所有可能组合的笛卡尔积(在这个例子中,8行而不是我们希望的4行).

SELECT xpath_int(xml, '/Reports/Report/@ID') AS id, location_id, location_name 
FROM   xmlreports 
LATERAL VIEW explode(xpath(xml, '/Reports/Report/Locations/Location/@ID')) myTable1 AS location_id 
LATERAL VIEW explode(xpath(xml, '/Reports/Report/Locations/Location/LocationName/text()')) myTable2 AS location_name;

查询2

试图分组成一个结构然后爆炸,但这会返回两行和两个数组.

SELECT id, loc.col1, loc.col2
FROM (
SELECT xpath_int(xml, '/Reports/Report/@ID') AS id, 
       array(struct(xpath(xml, '/Reports/Report/Locations/Location/@ID'), xpath(xml,     '/Reports/Report/Locations/Location/LocationName/text()'))) As foo
FROM   xmlreports) x
LATERAL VIEW explode(foo) exploded_table as loc;

结果

1   ["20001","20002"]       ["Irvine Animal Shelter","Irvine City Hall"]
2   ["10001","10002"]       ["California Fish Grill","Irvine Spectrum"]

我们想要的是什么

1   "20001" "Irvine Animal Shelter"
1   "20002" "Irvine City Hall"
2   "10001" "California Fish Grill"
2   "10002" "Irvine Spectrum"

看起来像是一件常见的事情,但却找不到任何例子.任何帮助是极大的赞赏.

Answer 1

我看到有两种方法可以解决这个问题。

1. 创建自定义 UDF，它将解析一个 XML 元素并返回您需要的数组。之后爆炸阵。

2. 使用子选择。

我使用子选择实现了解决方案 2。即使在使用子选择时，Hive 也“足够智能”，只为此创建一个映射缩减作业，所以我认为您不会遇到性能问题。

SELECT 
 l2.key,
 l2.rid,
 l2.location_id,
 location_name
FROM (
 SELECT 
  l1.key as key,  
  l1.rid as rid, 
  location_id as location_id,
  l1.xml as xml
 FROM (
   SELECT key, xml, rid
   FROM xmlreports
   LATERAL VIEW explode(xpath(xml, '/Reports/Report/@ID')) rids as rid
 ) l1
 LATERAL VIEW explode(xpath(l1.xml, concat('/Reports/Report[@ID = ',l1.rid, ']/Locations/Location/@ID'))) locids as location_id
) l2
LATERAL VIEW explode(xpath(l2.xml, concat('/Reports/Report[@ID = ',l2.rid, ']/Locations/Location[@ID = ', l2.location_id ,' ]/LocationName/text()'))) locnames as location_name;

对您提供的 XML 文件运行此查询后，我得到了您正在搜索的结果

1   1   20001   Irvine Animal Shelter
1   1   20002   Irvine City Hall
1   2   10001   California Fish Grill
1   2   10002   Fukada

希望这能解决您的问题。

问候，迪诺