binary: a sequence of unencoded bytes
N.B.: This is currently a specialized form of the string type above, added to provide better interoperability with Java. The current plan-of-record is to elevate this to a base type at some point.
The consequence is that, Thrift BINARY and STRING are both passed to parquet-thrift as STRING, and are always encoded as BINARY (UTF8).
This is really a problem on Thrift side. One possible workaround is to inspect binary fields in the actual generated Java classes to see whether the type is ByteBuffer.