Import this JSON File: { "BackupType" : "DBBackup", "Date" : "29-1-2015", "test": [{ "TeiidArray": [ { "_id": { "$oid" : "541087c3f706400030000002" } , "FirstName": "Eugene", "Score": [ "Korean", "100", "Medium" ], "LastName": "T", "CustomerID": 1 }, { "_id": { "$oid" : "541089051c4d5a0030000001" } , "FirstName": "Stas", "Score": [ "Japanese", "50", "Advance" ], "LastName": "C", "CustomerID": 2 }, { "_id": { "$oid" : "5410c969516cd50064000001" } , "FirstName": "Sally", "Score": [ "Russian", "90", "Advance" ], "LastName": "F", "CustomerID": 3 } ]}]} Create Schema like: CREATE FOREIGN TABLE TeiidArray ( ID String PRIMARY KEY, FirstName varchar(25), LastName varchar(25), Score object[] ) OPTIONS(UPDATABLE 'TRUE'); Run the following sql: select "FirstName" from "MongoDB_Array_263"."TeiidArray" group by "FirstName" order by "FirstName" limit 1000 Exception: Caused by: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 at java.util.ArrayList.rangeCheck(ArrayList.java:604) at java.util.ArrayList.get(ArrayList.java:382) at org.teiid.translator.mongodb.MongoDBQueryExecution.next(MongoDBQueryExecution.java:132) at org.teiid.dqp.internal.datamgr.ConnectorWorkItem.handleBatch(ConnectorWorkItem.java:386) at org.teiid.dqp.internal.datamgr.ConnectorWorkItem.more(ConnectorWorkItem.java:204) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at org.teiid.dqp.internal.datamgr.ConnectorManager$1.invoke(ConnectorManager.java:209) at $Proxy182.more(Unknown Source) at org.teiid.dqp.internal.process.DataTierTupleSource.getResults(DataTierTupleSource.java:301) at org.teiid.dqp.internal.process.DataTierTupleSource$1.call(DataTierTupleSource.java:110) at org.teiid.dqp.internal.process.DataTierTupleSource$1.call(DataTierTupleSource.java:107) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) at java.util.concurrent.FutureTask.run(FutureTask.java:166) at org.teiid.dqp.internal.process.FutureWork.run(FutureWork.java:58) at org.teiid.dqp.internal.process.DQPWorkContext.runInContext(DQPWorkContext.java:274) at org.teiid.dqp.internal.process.ThreadReuseExecutor$RunnableWrapper.run(ThreadReuseExecutor.java:119) at org.teiid.dqp.internal.process.ThreadReuseExecutor$3.run(ThreadReuseExecutor.java:210) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)