Suppose you have a custom UDF myUDF() that you've created to extend hive. The goal of this JIRA is to create a facility where if you run a query that uses myUDF() in an expression, the query will run in vectorized mode.
This would be a general-purpose bridge for custom UDFs that users add to Hive. It would work with existing UDFs.
I'm considering a separate JIRA for a new kind of custom UDF implementation that is vectorized from the beginning, to optimize performance. That is not covered by this JIRA.