我正在尝试使用pig解析带有嵌套标记的xml文件。我有下面的xml示例。

<Document>
    <medicationsInfo>
     <code>10160-0</code>
     <entryInfo> 
        <statusCode>completed</statusCode>
        <startTime>20110729</startTime>
        <endTime>20110822</endTime>
        <strengthValue>24</strengthValue>
        <strengthUnits>h</strengthUnits>
     </entryInfo> 
     <entryInfo>
        <statusCode>completed</statusCode>
        <startTime>20120130</startTime>
        <endTime>20120326</endTime>
        <strengthValue>12</strengthValue>
        <strengthUnits>h</strengthUnits>
     </entryInfo>
     <entryInfo>
        <statusCode>completed</statusCode>
        <startTime>20100412</startTime>
        <endTime>20110822</endTime>
        <strengthValue>8</strengthValue>
        <strengthUnits>d</strengthUnits>
     </entryInfo>  
    </medicationsInfo>
    <ProductInfo>
     <code>10160-0</code>
     <entryInfo> 
        <statusCode>completed</statusCode>
        <startTime>20110729</startTime>
        <endTime>20110822</endTime>
        <strengthValue>24</strengthValue>
        <strengthUnits>h</strengthUnits>
     </entryInfo> 
     <entryInfo>
        <statusCode>completed</statusCode>
        <startTime>20120130</startTime>
        <endTime>20120326</endTime>
        <strengthValue>12</strengthValue>
        <strengthUnits>h</strengthUnits>
     </entryInfo>
     <entryInfo>
        <statusCode>completed</statusCode>
        <startTime>20100412</startTime>
        <endTime>20110822</endTime>
        <strengthValue>8</strengthValue>
        <strengthUnits>d</strengthUnits>
     </entryInfo>  
    </ProductInfo>
   </Document>

我正在写下面的代码来获取药物结果的entryinfo信息，但是我得到了一个错误。
代码：

Register /home/cloudera/piggybank-0.16.0.jar;
DEFINE XPathAll org.apache.pig.piggybank.evaluation.xml.XPathAll();
DEFINE XPath org.apache.pig.piggybank.evaluation.xml.XPath();
A =  LOAD '/home/cloudera/Parsed_CCD.xml' using org.apache.pig.piggybank.storage.XMLLoader('medicationsInfo/entryInfo') as (x:chararray);
B = FOREACH A GENERATE XPathAll(x, 'statusCode',false,true), XPathAll(x, 'medicationsInfo/code/code',false,true).$0, XPathAll(x,'strengthValue',false,true).$1;
DUMP B;

错误：
[main]info org.apache.pig.backend.hadoop.executionengine.mapreducelayer.mapreducelauncher-失败[main]error org.apache.pig.tools.grunt.grunt-错误1066:无法打开别名b的迭代器
预期产量：

completed 20110729 20110822 24 h
completed 20120130 20120326 12 h
completed 20100412 20110822  8 d