@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "type")
public abstract class BigEvent implements Serializable {
}

> db.BigEvent.getIndexes()
[            
        ...    
        {                
                "v" : 1,         
                "key" : {
                        "type" : 1 
                },                                      
                "name" : "type_idx",
                "ns" : "ogm_test_database.BigEvent"
        }          
]