Insert fails when using union all

HUE version * 2.6.1-3485
hdp 2.3.4

insert overwrite table trn_operation
Select code , opcode from
(
select code , opcode from master
union all
select code, opcode from master
)as base;

when i give the union it inserts but when i give union all it gives error.

ERROR : Failed with exception checkPaths

at org.apache.hadoop.hive.ql.metadata.Hive.checkPaths(Hive.java:2491)
at org.apache.hadoop.hive.ql.metadata.Hive.replaceFiles(Hive.java:2905)
at org.apache.hadoop.hive.ql.metadata.Hive.loadTable(Hive.java:1659)
at org.apache.hadoop.hive.ql.exec.MoveTask.execute(MoveTask.java:298)
at org.apache.hadoop.hive.ql.exec.Task.executeTask(Task.java:160)