Hi,
> I'm hoping someone can help me shed some light on how Hive deals with
virtual columns.
The virtual column impl is not extensible in Hive, it is a fixed set of
enums.
https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/metadata/VirtualColumn.java#L64
However, according to the next comment, what you're looking for is a
time metadata column, which has a different pathway in the system & is
simpler than the complex struct ROW__ID impl.
> We are trying to implement some time travel features in a custom
input format we're building and are considering the approach of adding a
virtual column
See
https://github.com/apache/hive/blob/master/kafka-handler/src/java/org/apache/hadoop/hive/kafka/MetadataColumn.java#L63
which is used to produce time-travel queries over Kafka streams in Hive.
Cheers,
Gopal
