8

我们将 XML 数据作为名为 XML 的单个字符串列加载到 Hadoop 中。我们正在尝试检索数据级别并进行规范化或将其分解为单行以进行处理（您知道，就像一个表格！）尝试了分解功能，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，然后是子级的 id 和名称（Locations/Location）。下面给了我们所有可能组合的基本笛卡尔积（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

试图组合成一个结构然后分解，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"

似乎是一件很常见的事情，但找不到任何例子。任何帮助是极大的赞赏。

4

1 回答 1

3

我看到了两种解决这个问题的方法。

  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。在那之后爆炸阵列。

  2. 使用子选择。

我使用子选择实现了解决方案 2。即使使用 subselects Hive 是“足够聪明”来为此创建一个 map-reduce 作业，所以我认为你不会有性能问题。

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;

在您提供的 XML 文件上运行此查询后，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

于 2013-05-07T12:08:03.430 回答