xpath - 在 Hive 中爆破一行 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。我们正在尝试检索到数据级别，将其规范化或将其分解为单行以进行处理(你知道，就像一个表格!)已经尝试过分解函数，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，然后是子项 (Locations/Location) 的 ID 和名称。下面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

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

这似乎是一件很常见的事情，但找不到任何例子。非常感谢任何帮助。

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。在爆炸阵列之后。

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“足够聪明”为此创建一个 map-reduce 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;

在对您提供的 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，恐龙