Currently if in hive you have Avro or other formats, where the schema is complex, you cannot currently query the fields in the complex object via hcatalog/pxf integration.
In terms of Avro Schema - records, enums and complex arrays, do not work.
Hive fully supports this complex/object notation, as does many of the other SQL tools in the Hadoop eco-system (Spark, Impala, Drill).
These all seem to support the same styled solution of using dots for complex object/path negotiation:
SELECT schema.table.fieldA.nestedRecordFieldS FROM myavrotable;