UDTF failed with "org.apache.hadoop.hive.serde2.lazy.LazyString cannot be cast to org.apache.hadoop.io.Text"

Task with the most failures(4):
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Task ID:
  task_1436218099233_0158_m_000000

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Diagnostic Messages for this Task:
Error: java.lang.RuntimeException: org.apache.hadoop.hive.ql.metadata.HiveException: Hive Runtime Error while processing row {"a":"abc","b":"xyz"}
	at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:195)
	at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:54)
	at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:435)
	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:347)
	at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:168)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1566)
	at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:163)
Caused by: org.apache.hadoop.hive.ql.metadata.HiveException: Hive Runtime Error while processing row {"a":"abc","b":"xyz"}
	at org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:550)
	at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:177)
	... 8 more
Caused by: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.lazy.LazyString cannot be cast to org.apache.hadoop.io.Text
	at org.apache.hadoop.hive.serde2.objectinspector.primitive.WritableStringObjectInspector.getPrimitiveJavaObject(WritableStringObjectInspector.java:46)
	at org.apache.hadoop.hive.serde2.objectinspector.primitive.WritableStringObjectInspector.getPrimitiveJavaObject(WritableStringObjectInspector.java:26)
	at openkb.hive.udtf.DoubleColumn.process(DoubleColumn.java:64)
	at org.apache.hadoop.hive.ql.exec.UDTFOperator.processOp(UDTFOperator.java:107)
	at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:793)
	at org.apache.hadoop.hive.ql.exec.SelectOperator.processOp(SelectOperator.java:87)
	at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:793)
	at org.apache.hadoop.hive.ql.exec.TableScanOperator.processOp(TableScanOperator.java:92)
	at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:793)
	at org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:540)
	... 9 more

select * from testudtf;
abc	xyz

ADD JAR ~/target/DoubleColumn-1.0.0.jar;
CREATE TEMPORARY FUNCTION double_column AS 'openkb.hive.udtf.DoubleColumn'; 

SELECT double_column(a,b) as (a1,a2,b) FROM testudtf;
abc	abc	xyz