I use PostgreSQL.
Look at attached image.
When I tried to run Modelling->Preview Data I got:
[JDBCExecutionException] 0: Error Code:0 Message:'ERROR: "customer_pk" is an index
Position: 42' error executing statement(s): [Prepared Values: [] SQL: SELECT "public"."customer_pk"."ssn" FROM "public"."customer_pk"]
1 [PSQLException]ERROR: "customer_pk" is an index
Position: 42
at org.teiid.translator.jdbc.JDBCQueryExecution.execute(JDBCQueryExecution.java:88)
at org.teiid.dqp.internal.datamgr.ConnectorWorkItem.execute(ConnectorWorkItem.java:263)