The issue is that MergeTable gets a connection from a connection pool, and then assumes it is safe to set hive properties on the connection's session. With enough runs of many connected processors, this would create a merge of the properties from all processors in the connection.
In MergeTable.java line 191, onTrigger() method (407ee9246f68):
In TableMergeSyncSupport.java setHiveConf() method:
we now support reset in the MergeTable.
Another enhancement would be to add this reset to the Thrift Service itself to ensure every user gets sessions reset upon getting the connection.
Add property in controller service to 'reset' hive session upon new connection