Currently, the random query generator is run against postgres 9.3 for a reference database, but it needs postgres 9.5 features to better verify Impala/Kudu functionality. Specifically it's the ON CONFLICT clause here https://www.postgresql.org/docs/9.5/static/sql-insert.html . This is needed both to handle INSERT with implied IGNORE, which Impala will do, and UPSERT.
The validation should show that data migration and loading and query execution and comparison is possible. It's mostly a smoke/sanity test.