Getting Vertex failed error while executing merge query

[#1]

I'm trying to run a merge query in Hive. But it gives me this error every time. How do I resolve the same ?

java.sql.SQLException:
Error while processing statement: FAILED: Execution Error, return code 2 from
org.apache.hadoop.hive.ql.exec.tez.TezTask. Vertex failed, vertexName=Reducer
4, vertexId=vertex_1524056113553_0052_2_03, diagnostics=[Task failed,
taskId=task_1524056113553_0052_2_03_000000, diagnostics=[TaskAttempt 0 failed,
info=[Error: Failure while running task:java.lang.RuntimeException:
java.lang.RuntimeException: org.apache.hadoop.hive.ql.metadata.HiveException:
Hive Runtime Error while processing row (tag=0)
{"key":{"_col0":{"transactionid":2,"bucketid":1,"rowid":0},"_col1":"2018-05-02"},"value":{"_col0":1}}         
at org.apache.hadoop.hive.ql.exec.tez.TezProcessor.initializeAndRunProcessor(TezProcessor.java:173)
at org.apache.hadoop.hive.ql.exec.tez.TezProcessor.run(TezProcessor.java:139)
at org.apache.tez.runtime.LogicalIOProcessorRuntimeTask.run(LogicalIOProcessorRuntimeTask.java:347)
at org.apache.tez.runtime.task.TezTaskRunner$TaskRunnerCallable$1.run(TezTaskRunner.java:194)

[#2]

@Prathamesh H

Please check below KB -

https://community.hortonworks.com/content/supportkb/155515/error-javalangruntimeexception-hive-runti...